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1G Deceleration Chugs like Donkey at Low RPM and Bouncy Idle

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
So my NT 4g63 was overhauled but since the shop wasn't experienced around old engines it ran like crap.

Cold start idle were around 600 rpm, turning on AC would go down to 400-500, I unplugged the coolant temp sensor and idle got better (800-1k rpm). But the major problem is it "chugs" below 1500-1k rpm like slamming the throttle on-off until I clutch it in and smoothly press the throttle, it's really embarrassing around traffic since I can't let the car decelerate below 1500 rpm or it'll chug slowly until it reaches 1k where it jerks super violently. Accelerating at lower rpm, pressing the throttle slightly chugs violently then slowly goes away as rpm rises. Lastly it hesitates at low rpms.

So I emptied my wallet and bought some plugs (NGK BP6ES) and wires, fuel pump & filter and a used MAF sensor. Put those in then adjusted TPS, BISS, CAS and throttle cable finally car rans much more smoother, no more hesitation upon acceleration and even plugged the coolant sensor back in, the idle didn't crap out on me. It idles around 1k then bounces a little down to 950 without load but when AC is turned on it stabilizes at 950 rpm. But the major problem is still present, deceleration chugging and minor acceleration chugging at low rpms!

So far I'm guessing the TPS is on it's way out together with motor mounts since the mounts are all fabricated from junkyard rubbers and when chugging violently some clunking can be heard.
 

pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
How are you running a 2g maf with no mention of a tuning solution?
Do not throw any parts at it. Diagnose it one sensor at a time and get objective data. Guessing is an expensive way to fix the car.
Define "chugging".
If you're having to unplug anything to get it to run better that isn't a solution.
Check your mechanical timing.
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
How are you running a 2g maf with no mention of a tuning solution?
Do not throw any parts at it. Diagnose it one sensor at a time and get objective data. Guessing is an expensive way to fix the car.
Define "chugging".
If you're having to unplug anything to get it to run better that isn't a solution.
Check your mechanical timing.
Ohh right haven't updated my profile, I'm back running a stock 1g maf again. It's 1am in the morning so I'll check my car later when the sun shines. I'm also throwing parts at it since most of it are old and in need of replacing anyway, call it preventative maintenance if you will.

Chugging like as if you're tapping the throttle fully, something like near stalling jerking where it tries to keep the engine from dying but it does at 1k rpm so it's hard to keep it smooth especially at traffic.

Mechanical timing was also checked, cam gears lines up perfectly.
 

pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
Ohh right haven't updated my profile, I'm back running a stock 1g maf again. It's 1am in the morning so I'll check my car later when the sun shines. I'm also throwing parts at it since most of it are old and in need of replacing anyway, call it preventative maintenance if you will.
I will disagree on sensors. They typically work or they don't. If you have some laying around fine but do one at a time.

Chugging like as if you're tapping the throttle fully, something like near stalling jerking where it tries to keep the engine from dying but it does at 1k rpm so it's hard to keep it smooth especially at traffic.

Mechanical timing was also checked, cam gears lines up perfectly.
Cam gears aren't the only thing to check. Gear timing is RELATIVE to the crank. You must line up crank THEN check cams.

There are some basic things you can check and possibly you can rule these items out by unplugging them and taking a drive.
Does it free rev?
Have you checked ignition timing?
What happens if you unplug maf?
What happens if you unplug TPS?
Have you datalogged anything?
If so coolant temp? TPS functioning smoothly? o2 sensor? Is it closed loop or open loop? Is ISC functioning? Is idle position switch functioning?
Do you have any vacuum leaks?
Tell us what you've checked already.

 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
I will disagree on sensors. They typically work or they don't. If you have some laying around fine but do one at a time.


Cam gears aren't the only thing to check. Gear timing is RELATIVE to the crank. You must line up crank THEN check cams.

There are some basic things you can check and possibly you can rule these items out by unplugging them and taking a drive.
Does it free rev?
Have you checked ignition timing?
What happens if you unplug maf?
What happens if you unplug TPS?
Have you datalogged anything?
If so coolant temp? TPS functioning smoothly? o2 sensor? Is it closed loop or open loop? Is ISC functioning? Is idle position switch functioning?
Do you have any vacuum leaks?
Tell us what you've checked already.

[URL unfurl="true"
The mechanical timing was checked by a local DSM tuner (gvr4 to be more specific), so I took his word on that.

What do you mean by free rev?
Ignition timing was adjusted, idle is stable now
Unplugged maf runs like crap
Unplugged tps revs like crap
Dont own a datalogger
Unpugged coolant temp idle is jumpy
PH versions of NT galants didnt come with o2 sensors
ISC was replaced but nothing happens when unplugged

I dont own any fancy stuff like dataloggers, OBD scanners or Ohmeters. Im just a college kid trying to get by.
 

pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
The mechanical timing was checked by a local DSM tuner (gvr4 to be more specific), so I took his word on that.

What do you mean by free rev?
Ignition timing was adjusted, idle is stable now
Unplugged maf runs like crap
Unplugged tps revs like crap
Dont own a datalogger
Unpugged coolant temp idle is jumpy
PH versions of NT galants didnt come with o2 sensors
ISC was replaced but nothing happens when unplugged

I dont own any fancy stuff like dataloggers, OBD scanners or Ohmeters. Im just a college kid trying to get by.
Free rev is just rev it up in neutral. Does it do this?
It has o2 sensors. It has to if it's ecu controlled.
Do you have a cel? You can buy a cheap analog meter for 10$ to check codes, do minor checks etc.
 

waltah

10+ Year Contributor
369
154
Mar 2, 2011
fairfield, Virginia
So my NT 4g63 was overhauled but since the shop wasn't experienced around old engines it ran like crap.

Cold start idle were around 600 rpm, turning on AC would go down to 400-500, I unplugged the coolant temp sensor and idle got better (800-1k rpm). But the major problem is it "chugs" below 1500-1k rpm like slamming the throttle on-off until I clutch it in and smoothly press the throttle, it's really embarrassing around traffic since I can't let the car decelerate below 1500 rpm or it'll chug slowly until it reaches 1k where it jerks super violently. Accelerating at lower rpm, pressing the throttle slightly chugs violently then slowly goes away as rpm rises. Lastly it hesitates at low rpms.
Do three things:

1. Set the throttle stop screw (Phillips head with a locknut) on the side of the throttle body with the spring and cable) 1-1/4 turns toward 'more throttle' from the closed throttle position. I would write you a guarantee that your mechanic diddled this in an attempt to set the idle RPM.

To do this back the screw out a few turns and the nut a bit more then with the throttle closed under spring tension (don't force it) turn the screw in until you feel it just touch the throttle. Go 1-1/4 turns more and tighten the locknut. Until this setting is right, nothing else can be correctly adjusted.

2. Use a cheap analog multimeter on OHMS to check between the top two pins (pins 3-4) of the throttle position sensor. This is the round black thing on the top front of the throttle valve assembly. Those pins are the closed throttle position switch: They tell the ECU 'His foot is off the gas so you, dear computer, must control the RPM.' With the throttle closed there should be a near short -- my old cars typically show 20=40 ohms but a new switch should be ~0. While monitoring the switch, open the throttle just a little. The switch should go to 'open circuit.' If it doesn't or if it isn't a short with the throttle closed then back out the two hex head screws that hold the Throttle Position Sensor (TPS) and rotate the sensor until it works right -- switch is closed with throttle closed, switch is open with a slight throttle movement.

The rest of the TPS is a potentiometer that gives the ECU and auto transmission (if that's what you have) info about how far open the throttle is. The transmission uses that info to adjust shift points, the ECU uses it in calculating injector times. This potentiometer is not separately adjustable: There are specs for it in the manual and if when the closed throttle position switch is set right, the TPS potentiometer is out of spec it must be replaced. That problem is uncommon compared to the others just mentioned.

3. Disconnect the battery for half a minute to reset the codes, then do a drive. See what's happened to your symptoms and if you get a CE light. If you do, get one of the auto parts places -- Advance Auto, O'Reilly, whatever -- to read the code(s) for you.

Almost all of our cars have by now met a mechanic who thinks 'Old Car!' and goes in with a screwdriver to adjust the throttle stop screw to set the idle speed. These cars will never run right -- your symptoms are standard -- until this is fixed. The idle speed on these cars is controlled by the ECU. It varies a little from one model to another -- I don't know the 1G number -- but it's usually 750 or 850 RPM and a bit higher with the A/C on. There is no adjustment to change that unless you get one of the programmable ECUs and do it there.
 

pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
I'll add to this. The idle position switch will never work unless the throttle body is grounded. There is a ground strap on the front of the throttle body that looks like a bracket that does nothing. There is also a ground on the intake manifold to firewall. These both must be present.
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
Alright, I've ordered a cheap multimeter and a new TPS, before anyone asks why buy a TPS it's because the one installed has the whole bottom end where the lower bolt is screwed are gone so it's hanging by the upper bolt and jiggles around. Plus at the top part of the TPS housing has a gaping hole, probably because of the mechanic hitting it with the 8mm wrench head when tightening the bolt.

In the meantime to make my car useable without proper tuning, I tightened the IPS to about 3/4 so it doesn't dip below 1k RPM when coasting therefore making the chugging to very minimal or none at all on accel and decel then adjusted the BISS to compensate the ridiculous tune I did. Of course the downside is it idles at 1100 RPM and dips to 950 with accessory load.

Yes it's the typical dumb crap that college kids do, and I am that typical dumb college kid. But once the multimeter and TPS arrives together with a clear schedule, I'll tune it properly.
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
Do three things:

1. Set the throttle stop screw (Phillips head with a locknut) on the side of the throttle body with the spring and cable) 1-1/4 turns toward 'more throttle' from the closed throttle position. I would write you a guarantee that your mechanic diddled this in an attempt to set the idle RPM.

To do this back the screw out a few turns and the nut a bit more then with the throttle closed under spring tension (don't force it) turn the screw in until you feel it just touch the throttle. Go 1-1/4 turns more and tighten the locknut. Until this setting is right, nothing else can be correctly adjusted.

2. Use a cheap analog multimeter on OHMS to check between the top two pins (pins 3-4) of the throttle position sensor. This is the round black thing on the top front of the throttle valve assembly. Those pins are the closed throttle position switch: They tell the ECU 'His foot is off the gas so you, dear computer, must control the RPM.' With the throttle closed there should be a near short -- my old cars typically show 20=40 ohms but a new switch should be ~0. While monitoring the switch, open the throttle just a little. The switch should go to 'open circuit.' If it doesn't or if it isn't a short with the throttle closed then back out the two hex head screws that hold the Throttle Position Sensor (TPS) and rotate the sensor until it works right -- switch is closed with throttle closed, switch is open with a slight throttle movement.

The rest of the TPS is a potentiometer that gives the ECU and auto transmission (if that's what you have) info about how far open the throttle is. The transmission uses that info to adjust shift points, the ECU uses it in calculating injector times. This potentiometer is not separately adjustable: There are specs for it in the manual and if when the closed throttle position switch is set right, the TPS potentiometer is out of spec it must be replaced. That problem is uncommon compared to the others just mentioned.

3. Disconnect the battery for half a minute to reset the codes, then do a drive. See what's happened to your symptoms and if you get a CE light. If you do, get one of the auto parts places -- Advance Auto, O'Reilly, whatever -- to read the code(s) for you.

Almost all of our cars have by now met a mechanic who thinks 'Old Car!' and goes in with a screwdriver to adjust the throttle stop screw to set the idle speed. These cars will never run right -- your symptoms are standard -- until this is fixed. The idle speed on these cars is controlled by the ECU. It varies a little from one model to another -- I don't know the 1G number -- but it's usually 750 or 850 RPM and a bit higher with the A/C on. There is no adjustment to change that unless you get one of the programmable ECUs and do it there.
Hey thanks a lot for a very detailed guide, I really appreciate it and once the Multimeter and TPS arrives I'll follow what you wrote here. From what I've read, Steve said the factory idle goes about 750+- so I'll aim for that. Will post an update regarding this too!
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
I'll add to this. The idle position switch will never work unless the throttle body is grounded. There is a ground strap on the front of the throttle body that looks like a bracket that does nothing. There is also a ground on the intake manifold to firewall. These both must be present.
The intake mani has a ground but the TB does not, I'll take a photo tomorrow of it since I can't find where the ground strap hooks up to. But even without it, the IPS has feedback to the ECU since the idle gets jumpy when its not tuned properly but plugged in, and unplugging it idles high?
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
This pic is from a 90 but the concept is the same. The strap is just basically a wire. The thread will explain.

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Here's my TB (on the left) compared to the 90' TB with the ground strap circulating around in this forums, it's completely different and I don't see where the Philips head should screw in even if it has a ground strap.

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pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
Here's my TB (on the left) compared to the 90' TB with the ground strap circulating around in this forums, it's completely different and I don't see where the Philips head should screw in even if it has a ground strap.

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More photos:

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That isn't the original throttle body. Its a non turbo throttle body. Nt throttle body doesn't use a ground strap because the body isn't Insulated from the manifold. The bolt head touches the actual throttle body. On a turbo throttle body there is an elbow separated by a gasket so the bolt can't act as a good ground to the throttle body necessitating the bracket.
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
That isn't the original throttle body. Its a non turbo throttle body. Nt throttle body doesn't use a ground strap because the body isn't Insulated from the manifold. The bolt head touches the actual throttle body. On a turbo throttle body there is an elbow separated by a gasket so the bolt can't act as a good ground to the throttle body necessitating the bracket.
That is the original throttle body... Like I said on the original post, it's a NT 4G63, my car is a Galant GTi-16v, they come with a NT 4G63 but look exactly like a VR-4 would except it's a FWD non turbo.

If you got confused by my vehicle profile stating it's a VR-4, it because there's no GTi trim version available to choose from, only VR-4 and GSX.
 
Last edited:

waltah

10+ Year Contributor
369
154
Mar 2, 2011
fairfield, Virginia
Hey thanks a lot for a very detailed guide, I really appreciate it and once the Multimeter and TPS arrives I'll follow what you wrote here. From what I've read, Steve said the factory idle goes about 750+- so I'll aim for that. Will post an update regarding this too!
You do not have a choice about the idle RPM. Either the ECU controls it and it is correct -- Steve knows these cars better than I do so 'correct' is probably 750 -- or the ECU isn't controlling it and it varies giving you a car that does weird stuff.

Here's how it works. RPM is set by the amount of air entering the engine. At idle, air gets there three main ways:

1. Some goes past the throttle plate. This is set by how far the throttle is open when your foot is off the pedal which is controlled by the throttle stop screw. This is a FIXED setting, should always be 1-1/4 turns unless your model is different from most of them -- you'd need a manual or an expert to know that. Go with 1-1/4 until someone tells you otherwise. Basically the purpose of this setting is to keep the throttle from jamming in the bore and give the right rate of air increase as you start to apply throttle.

2. Some goes through a separate passage controlled by the Basic Idle Speed Screw (BISS). This sets the total fixed air (never altered during operation) so that the Idle Speed Control (ISC) can operate correctly, neither going all the way closed to reduce air on hot idle nor lacking the range to give a good fast idle on an extreme cold morning. There's a procedure to set it but the way I've done it is to open the screw two turns from closed then tweak it until both cold fast idle and hot idle speed are okay.

3. And the rest of the idle air goes through the ISC -- a valve that is controlled by the ECU so that:

A. Warm idle is 750 RPM. YOU DO NOT HAVE A CHOICE ABOUT THIS NUMBER. It's in the ECU and you only change it there with a programmable one.
B. Accessory loads -- A/C, alternator, power steering -- don't slow the engine down and the A/C actually speeds it up by 100 RPM or so. ('idle up' function.)
C. When you are cruising and take your foot off the pedal abruptly, the engine does not stall but slows gradually to a correct idle RPM. ('dashpot' function.) Stalling at stop signs is often a symptom of an ISC that isn't working, most commonly because someone diddled the screws without knowing how.

The ECU then controls the amount of fuel that's injected to give the proper fuel/air mixture. This is done just from an ECU table when the engine is cold and altered by the 02 sensor in the exhaust manifold once that sensor is warm enough to operate -- 'closed loop operation.'

One input to the fuel amount is the TPS rheostat info about 'just how far open is the throttle'? If you have the stop screw wrong this will be wrong and even with the idle okay, the engine may try to die when you come off closed throttle.

The overall setup procedure is:

1. Set the throttle stop screw (Phillips head with lock nut) to 1-1/4 turns. This must be set first because it affects the next setting. It is on the side of the throttle body that's next to the firewall and is visible (head is toward you) from the passenger side below the throttle shaft. Not an easy place to adjust but it's supposed to be set at the factory and left alone: The only reason to touch it is the likelihood that it's been set incorrectly.

I've gotten to assuming that if one of these cars doesn't idle right, this screw has likely been fiddled with and the whole procedure must be done. Both of my Eclipses and at least a couple of the Expo LRVs were wrong.

2. Adjust the TPS so the closed throttle position switch is closed when the throttle is closed and opens promptly when the throttle opens. THIS SWITCH TELLS THE ECU TO TAKE CHARGE OF THE IDLE SPEED. If it's not doing that job the idle RPM will be wrong and not properly controlled -- accessories may bog the motor, hot idle may be too fast, there may not be enough fast idle to avoid repeated stalls on a cold morning, and car may stall at stop signs.

3. Adjust the BISS starting at 2 turns open and tweaking by 1/4 turns until you have proper hot idle (750 unless the A/C is running) and a definite fast idle on a cold engine. The BISS is in the hole on forward side of the top of the throttle body. It has one of those combo Phillips/straight heads so either screwdriver can be used. There should be a rubber plug in the hole but as on your car they are often missing.

Example: After doing 1 & 2 above you set the BISS at 2 turns. When the car is warmed up the idle is 1200 -- WAY too fast. Crank 'er in by 1/4 turns until the fast idle is 750. At this point 1/4 turn more will probably make no difference in the RPM -- you reduce the idle air with the BISS, but the ISC is cranked out by the ECU to keep the RPM right. Let it be until you've had a chance to drive it a bit and see that it has a correct fast idle on cold starting.

A damaged TPS must be replaced as you are doing. I have an 8 mm 1/4" drive socket that I've ground thin so it can be used on those screws without damaging the thing but an open end wrench will also work -- just really awkward. Just be glad your TPS is on the front side: Some models have it against the firewall and you have very little room and must work by feel.

Yes it's the typical dumb crap that college kids do, and I am that typical dumb college kid
Seems to me you're doing fine.
 

pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
That is the original throttle body... Like I said on the original post, it's a NT 4G63, my car is a Galant GTi-16v, they come with a NT 4G63 but look exactly like a VR-4 would except it's a FWD non turbo.

If you got confused by my vehicle profile stating it's a VR-4, it because there's no GTi trim version available to choose from, only VR-4 and GSX.
That's fine. Either way that style of throttle body does not have a strap because it doesn't need one.
 

1990TSIAWDTALON

Moderator
9,440
5,268
Nov 14, 2013
Independence, Kansas
When I have a TPS off of my TB, I like to replace those cap screws with allen head screws, it makes adjusting my TPS much easier with an allen wrench (which is also made a little shorter so it will fit in that cramped space).
Just a tip.
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
You do not have a choice about the idle RPM. Either the ECU controls it and it is correct -- Steve knows these cars better than I do so 'correct' is probably 750 -- or the ECU isn't controlling it and it varies giving you a car that does weird stuff.

Here's how it works. RPM is set by the amount of air entering the engine. At idle, air gets there three main ways:

1. Some goes past the throttle plate. This is set by how far the throttle is open when your foot is off the pedal which is controlled by the throttle stop screw. This is a FIXED setting, should always be 1-1/4 turns unless your model is different from most of them -- you'd need a manual or an expert to know that. Go with 1-1/4 until someone tells you otherwise. Basically the purpose of this setting is to keep the throttle from jamming in the bore and give the right rate of air increase as you start to apply throttle.

2. Some goes through a separate passage controlled by the Basic Idle Speed Screw (BISS). This sets the total fixed air (never altered during operation) so that the Idle Speed Control (ISC) can operate correctly, neither going all the way closed to reduce air on hot idle nor lacking the range to give a good fast idle on an extreme cold morning. There's a procedure to set it but the way I've done it is to open the screw two turns from closed then tweak it until both cold fast idle and hot idle speed are okay.

3. And the rest of the idle air goes through the ISC -- a valve that is controlled by the ECU so that:

A. Warm idle is 750 RPM. YOU DO NOT HAVE A CHOICE ABOUT THIS NUMBER. It's in the ECU and you only change it there with a programmable one.
B. Accessory loads -- A/C, alternator, power steering -- don't slow the engine down and the A/C actually speeds it up by 100 RPM or so. ('idle up' function.)
C. When you are cruising and take your foot off the pedal abruptly, the engine does not stall but slows gradually to a correct idle RPM. ('dashpot' function.) Stalling at stop signs is often a symptom of an ISC that isn't working, most commonly because someone diddled the screws without knowing how.

The ECU then controls the amount of fuel that's injected to give the proper fuel/air mixture. This is done just from an ECU table when the engine is cold and altered by the 02 sensor in the exhaust manifold once that sensor is warm enough to operate -- 'closed loop operation.'

One input to the fuel amount is the TPS rheostat info about 'just how far open is the throttle'? If you have the stop screw wrong this will be wrong and even with the idle okay, the engine may try to die when you come off closed throttle.

The overall setup procedure is:

1. Set the throttle stop screw (Phillips head with lock nut) to 1-1/4 turns. This must be set first because it affects the next setting. It is on the side of the throttle body that's next to the firewall and is visible (head is toward you) from the passenger side below the throttle shaft. Not an easy place to adjust but it's supposed to be set at the factory and left alone: The only reason to touch it is the likelihood that it's been set incorrectly.

I've gotten to assuming that if one of these cars doesn't idle right, this screw has likely been fiddled with and the whole procedure must be done. Both of my Eclipses and at least a couple of the Expo LRVs were wrong.

2. Adjust the TPS so the closed throttle position switch is closed when the throttle is closed and opens promptly when the throttle opens. THIS SWITCH TELLS THE ECU TO TAKE CHARGE OF THE IDLE SPEED. If it's not doing that job the idle RPM will be wrong and not properly controlled -- accessories may bog the motor, hot idle may be too fast, there may not be enough fast idle to avoid repeated stalls on a cold morning, and car may stall at stop signs.

3. Adjust the BISS starting at 2 turns open and tweaking by 1/4 turns until you have proper hot idle (750 unless the A/C is running) and a definite fast idle on a cold engine. The BISS is in the hole on forward side of the top of the throttle body. It has one of those combo Phillips/straight heads so either screwdriver can be used. There should be a rubber plug in the hole but as on your car they are often missing.

Example: After doing 1 & 2 above you set the BISS at 2 turns. When the car is warmed up the idle is 1200 -- WAY too fast. Crank 'er in by 1/4 turns until the fast idle is 750. At this point 1/4 turn more will probably make no difference in the RPM -- you reduce the idle air with the BISS, but the ISC is cranked out by the ECU to keep the RPM right. Let it be until you've had a chance to drive it a bit and see that it has a correct fast idle on cold starting.

A damaged TPS must be replaced as you are doing. I have an 8 mm 1/4" drive socket that I've ground thin so it can be used on those screws without damaging the thing but an open end wrench will also work -- just really awkward. Just be glad your TPS is on the front side: Some models have it against the firewall and you have very little room and must work by feel.


Seems to me you're doing fine.
Hey thanks for the in depth and thoroughly input again, this will definitely help once the things I need arrive.

Question though, the ISC does not need any adjustment correct? It's a new one for approximately 6 months but I didn't feel any change when I installed it, the idle still lowers once load is added. Could it be working but since the other sensors are improperly tuned, it isn't doing it's job the right way?
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
When I have a TPS off of my TB, I like to replace those cap screws with allen head screws, it makes adjusting my TPS much easier with an allen wrench (which is also made a little shorter so it will fit in that cramped space).
Just a tip.
Hey that's a great idea, I'll drop by the hardware store when I get the chance. This will lessen the hassle of removing the TB when installing and tuning the TPS big time!
 

pauleyman

DSM Wiseman
8,182
2,753
Nov 19, 2011
oklahoma city, Oklahoma
Hey thanks for the in depth and thoroughly input again, this will definitely help once the things I need arrive.

Question though, the ISC does not need any adjustment correct? It's a new one for approximately 6 months but I didn't feel any change when I installed it, the idle still lowers once load is added. Could it be working but since the other sensors are improperly tuned, it isn't doing it's job the right way?
You do not adjust isc. You adjust biss. Isc makes adjustments on the fly within a certain range of motion. You ensure that range is optimal by setting biss correctly. This will explain.
 

waltah

10+ Year Contributor
369
154
Mar 2, 2011
fairfield, Virginia
Question though, the ISC does not need any adjustment correct? It's a new one for approximately 6 months but I didn't feel any change when I installed it, the idle still lowers once load is added. Could it be working but since the other sensors are improperly tuned, it isn't doing it's job the right way?
Just as Paul and you say: The ISC just follows orders. With the adjustable things not working right the ECU is getting bad inputs and telling the ISC to do wrong things.

You're gonna like your car a lot better once you untangle this small mess!
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
Alright update, the multimeter came but the new TPS is still being delivered, however I can't resist and did the tune Waltah posted in this thread.

Adjusted the IPS just enough for the switch to touch the throttle whlist not adding tension that can cause the throttle to open and also not stick when closed. (Note that the screw on the IPS wasn't fiddled since I got this from a junkyard so I didn't messed with it). IPS has continuity on closed throttle, moving on to the TPS I turned the key to "ON" and adjusted the TPS the best I could. The lowest I got was 85+ ohms, any other adjustments goes higher on closed throttle so I left it with that since a new TPS is on the way. Next up was the BISS which was turned all the way in then backed out 2 turns, I unplugged the battery then left it for a while then plugged it to reset the codes.

Car stalls on cold start so I upped the BISS by 2 more turns then it idled around 700-750, let it sit for about 5 mins then tried the AC which still bogs the idle to 600-650. Took it for a test drive and the chugging was almost minimal, accel was more smoother albeit a little chugging same goes for decel but it only occurs below 1k. I haven't driven it a lot since I was in the middle of replacing my shifter cable bushings for skateboard bearings and it's a long story, but once the TPS arrives I'll throw another update.
 

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia

cmp1516

Proven Member
52
20
Aug 2, 2021
Quezon City, Asia
Just as Paul and you say: The ISC just follows orders. With the adjustable things not working right the ECU is getting bad inputs and telling the ISC to do wrong things.

You're gonna like your car a lot better once you untangle this small mess!
Understood, we'll see once I've finalize the tweaks.

This thing pulls hard although I do miss my 1980's Lancer, just a simple carburetor to adjust air/fuel ratio and it's good to go.
 
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