WEIRD idle surge...kind of

[ramsack]

my car idles fine, but when coming to a stop, ONLY if the car is moving, even a slight bit, it will idle surge (slower than usual surge) until the car is completely stopped, and then return to normal idle. when i say slower than usual, it bounces between idle and ~1500 slower than if you unplug the IAC. there aren't any boost leaks that i'm aware of (been tested) or vacuum leaks. TPS is good and adjusted correctly. didn't test the idle switch yet. the IAC is also in spec last time i checked, and when i unplug it the car does it fast up/down surge. this is really getting annoying and it just started. oh and my FIAV is completely ripped out and blocked off. i JB-welded a piece of pipe in there. the idle misses a bit sometimes if i'm sitting in a drive-through waiting for food. new plugs, new wires. what else is there to check?

 

[1995gsx20g]

when you are moving the ecu takes into account that you are moving via speed sensor on the tranny and if you are in neutral it will bump up the idle to take into account that when you step on the brakes vacuum decreases and your car may stall if rpm is at 750. so it keeps it above. im pretty sure you still have a small idle issue that is hiding and only being viewed by you when your coasting.
-how is the throttle cable tension?
-spray the coil with water while running the car in the dark. it will miss and the arc will show better in the darkness.
-many people including myself have over looked the fact that the intake pipe between the mas and turbo also counts. and will not show up on a blt.

 

[ramsack]

the throttle cable is kind of a design of my own. i cut it off the cruise control itself and got a little metal piece with a set screw that resembles the solder bead that comes stock where the cable goes to the throttle body. the cable is kinda bent where it goes to the throttle body because of being wrapped around a pulley inside the CC its whole life. long story short it has a lot of slack. when putting the tps on i adjusted it to i think 0.49 volts, and it shows up on mmcd as 10%. just wondering if this has anything to do with anything at all. i just sprayed the coils with water and no arcing. what should i look for with the intake pipe? just cracks? also i have a missing problem sometimes while driving. very random, and very rare. the car cuts out, and flashes the CEL and it's code 44. BUT i can also hear the MPI relay click out when it does this. i'm thinking it's my ecu. it had leaking caps and i replaced them, but nothing else. other components (SMD) that looked afftected tested good on the multimeter. i know it can't be any of the black drivers on the board either, because the IAC is good and functions. there is just something causing the car to over-rev while coasting.

EDIT: to add, i've been swapping in and out my fuel rail a lot lately because a put a gauge on the rail itself and it kept leaking. i tore off the intake manifold a little bit ago, cleaned it, cleaned the TB. the gasket between the manifold and head had chunks missing out of it. needless to say i did have a surge problem then. anyway, i also replaced the injector to head insulators. when i took my rail out the first time recently i discovered one of the insulators was kind of torn, so my friend gave me one that was good looking. it's not as soft as the others. but this problem started just the other day, probably a week or so after the last time i touched the rail. also every time i put the rail back in i carefully positioned it and all the seals as to not tear them.

 

[1995gsx20g]

if i was able to visually see how your cable is modded i would better understand but from what you tell me i don't think i like the bend. but i was looking for to much tension when referring to throttle cable tension. if you can't get an proper setting with your tps it could be your cause right there.
what is this code 44?

 

[ramsack]

it is under-tensioned. also it does open all the way, and it does close all the way. i'm just wondering why i adjust the TPS how the manual says, and even in MMCD it will show the same voltage as my multimeter, but just says 10%. code 44 is for the power transistor i believe. if it isn't 44, it's a power transistor code. which why would the power transistor cause the MPI relay to shut off? it seems like the whole ECU shut off IMO.

 

[1995gsx20g]

-do you have all of the proper springs on the tb and at the proper number of time winded?
-i believe the power transistor is the reason you have random misfires and the car dies.
-i had a hard time setting like the manual says so i just kept guessing and checking until i got it right. if you go to far you will give it gas and the car will bog or be unresponsive until you give it more gas. if you adjust it the opposite way to much it will buck when trying to move from a stop. and in between shifts at normal speeds.

 

[ramsack]

yes, the throttle body hasn't been taken apart ever. the car doesn't die. if it ever does it is after i just beat the piss out of it, and i restart it, and it runs fine. i'm not even going to bother trying (buying) another power transistor because i want a dynatek arc-2. and there is no way to actually test the power transistor because it is a solid state device. it either works or it doesn't. i adjusted the TPS according to the vfaq and how everyone else does. i just stuck 2 tiny pins in the 2 proper wires and adjusted until i got .48-.50 volts. the car drives fine except it has no power because it is constantly knocking. it is a turbo car with an n/a bottom end. i also have a walbro 255hp in there and my fuel pressure is about 8 psi higher due to FPR overrun. it is running rich, but not too too rich. it was really running like crap the other week, which is why i put the fuel pressure gauge on, and found out the FPR that was on there was bad and giving me almost 60 psi of base fuel pressure. now it runs 42-44 psi and it still boosts like ASS.

 

[1995gsx20g]

i don't know how a 1g ecu handles it but i have a 255 and no regulator yet its in the mail finally and it boosts pretty good but this is in a 2g. do you have any mods done to your honeycomb in the mas?
what mods do you have?

 

[ramsack]

only mods are the 255hp, the fuel pressure gauge, and my exhaust is cut off where the cat attaches. i have the 255 high pressure. if you have a regular 255 then you are less likely to have overrun. the ecu is blind to fuel mods anyway. the maf is unhacked. i have no vacuum lines except the FPR and BOV. the wastegate is connected right to the compressor housing, so i am running ~10 psi of boost.

 

[1995gsx20g]

i have the high pressure. but this may help you.
SYMPTOM DESCRIPTION:

The engine runs unevenly at idle. If bad enough, the vehicle may shake. Also, the idle may vary in rpm (called "hunting"). Either condition may be severe enough to cause stalling. Engine idles at incorrect speed.

SYSTEM OR COMPONENT TO CHECK ACTION
COMPUTER INPUTS/OUTPUTS CHECK: - OXYGEN SENSOR (O2) -

Inspect sensor for silicon contamination
from fuel, or use of improper RTV sealant.
The sensor will have a white, powdery coating,
coating, and will result in a high but
false signal voltage (rich exhaust).
The Control Unit will then reduce the
amount of fuel being delivered to the
engine, causing a driveability problem.
Refer to COMPONENT TEST PROCEDURES.

* THROTTLE POSITION SENSOR (TPS) - If a sticking throttle shaft or binding linkage

causes a high TPS output voltage.
Refer to COMPONENT TEST PROCEDURES.

* COOLANT TEMPERATURE SENSOR (CTS) - Compare coolant temperature

with ambient temperature on a cold engine.
If coolant temperature reads 5 degrees
greater than or less than ambient air
temperature. Check for high resistance
in coolant sensor circuit or sensor itself.
Refer to COMPONENT TEST PROCEDURES.

* MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR - Test sensor for response and accuracy.

Refer to COMPONENT TEST PROCEDURES.

* CONTROL UNIT - Check grounds for being clean,

tight, and in their proper location.

* IDLE SPEED CONTROLS Check operation of Stepper Motor, Actuator,

or Sole-Vac Throttle Positioner.
Refer to COMPONENT TEST PROCEDURES.

* A/C SELECT SWITCH Check to see that the Control Unit

is receiving an input signal indicating
A/C system activation.
Refer to COMPONENT TEST PROCEDURES.
If problem exists with A/C ON, check
A/C System operation.

FUEL CHECK: - FUEL PRESSURE

* FUEL INJECTOR BALANCE TEST

IGNITION CHECK: - SECONDARY AND PRIMARY SYSTEM.
- IGNITION TIMING.
EMISSIONS CHECK: - EVAPORATIVE SYSTEM
- EGR SYSTEM
- PCV VALVE
- AIR MANAGEMENT SYSTEM.

Refer to Powertrain Management/Emission Control Systems/Testing and Inspection/Procedures.

ENGINE CHECK: - VACUUM LEAKS

Can cause higher than normal idle speeds.
- BATTERY
Cables and ground straps should be
clean and secure.
Erratic voltage will cause poor idle quality.
- A/C SYSTEM
Refrigerant pressure too high,
overcharge or faulty high pressure switch.
- MOTOR MOUNTS.
- CYLINDER COMPRESSION.

 

[ramsack]

o2 sensor - this is functioning properly. the voltage fluctuates and is usually around 0.8v. there is no silicone on it.

TPS - this is functioning properly.

coolant temp. sensor - this is functioning properly. i checked it earlier today while the car was warm. was about 500 ohms which should be around ~160 degrees.

these cars have no map sensors.

ECU - definitely a suspect. don't know where i can get one just to test.

idle speed control - IAC is good and within specifications. i put in another IAC i have, the newer 40 ohm style that is black. the car idled low for a while and the rising idle while coasting stopped until i reset the car.

a/c select switch - i don't have a/c

fuel check - as stated before pressure is ~44 psi which is ~8 psi too high. car ran like crap at ~60 psi fuel pressure with a bad FPR, and this 44 psi made it run a little better, but not quite there.

ignition - timing is DEAD on 5 degrees BTDC. wires are a few weeks old ngk wires. basically oem specs. plugs are bpr7es gapped at .028" coil is not arcing.

emissions - i don't have any left. the port on the intake manifold for the PCV valve is actually plugged because IMO these PCV valves suck and leak boost. the EGR is simply unplugged but not blocked off.

vacuum leaks - yea they can pop up at any time. i really have to do a boost leak test to see if anything after the turbo is leaking again.

motor mounts - not in the greatest shape, but whoever had it before jammed some metal rods in there to stiffen them up, so the engine doesn't really move.

compression - 210 psi across the board

when i first got this car back together, it ran like a CHAMP. the only way i know how to describe it is that it felt like a bone stock 3000gt vr-4. i mean a torquey SOB. now it just has tons of knock. on MMCD it was getting like 40-some counts. i don't have a PDA to datalog again, i was just borrowing it for a few minutes to look things over. i have a 160 degree thermostat in the car because i worry about head temperatures high and causing knock being 9:1. also the car is just running like it is a better in partial throttle, but that's knock related. i am trying to get money to get an AFPR kit and fuel supply kit from STM. also, injectors are 2g 450's.

a while ago i got on it in 1st gear and there was a loud pop, and the car has been running like crap ever since. a few days later i did a boost leak test and found the j-pipe flange was warped and leaking. put another one on and there was absolutely no boost leaks that could be heard. i really wouldn't see how if there was a slow slow leak that just barely makes soapy water bubble up cause a huge difference in MAS readings, but that's just my opinion.

 

[ramsack]

did a boost leak test tonight and heard air leaking around the throttle body area. moving the throttle revealed it is the shaft seal on the side where the cable goes.

 

[BLINKY619]

Yea those tend to leak alot...! By the way were do you get the shaft seals i mean ive tried the dealership but they dont have them there were should i look...! I have the same problem

 

[ramsack]

machv.com has them for $12 a pair.

 

[steve]

compression - 210 psi across the board

That's strange, what compression are you running. A perfect 1G turbo engine wouldn't be over 160psi.

 

[ramsack]

it is a non-turbo bottom end. bought the car like that. that's why i said it felt like a 3000gt when it was running good before.

 

[steve]

Good luck with that.

 

[1995gsx20g]

when in doubt break out the check list, glad you found your problem

 

[fwd4g63tsi]

Can anyone name all the censors that effect the idle in a 1g and how to test each one.

thank you in advance if anyone can help

 

[ramsack]

really, any sensor CAN affect idle, just all differently. there are factiory pdf manuals floating around somewhere, just search.

 

[1995gsx20g]

Can anyone name all the censors that effect the idle in a 1g and how to test each one.

thank you in advance if anyone can help

read post 10. this is copied from a service manual

 

[fwd4g63tsi]

Thank you for the help

 

[ramsack]

yeah, so i replaced the TB shaft seals today after work. definitely runs much better, but i still have an idle surge while coming to a stop. i'm calling ECU on this one mainly because the other day it wouldn't start and the MPI relay was clicking and buzzing all to hell. also i tried to put a dynatek arc-2 on, with brand new coils and plug wires, and it wouldn't run, so i'm thinking the capacitors that are messing with the MPI relay might also be causing the arc-2 to misfire. either that or i need plug wires and plugs with much lower resistance since high resistance wires are meant for inductive ignitions like the stock is, and from what i understand a capacitive ignition likes lower resistance wires.

 

[ramsack]

i grounded the timing connector and the pin 10 on the diagnostics connectors and adjusted the idle. it got better and stopped surging. idle didn't go above 1000 rpm while moving. now the past few days its back to creeping towards 1500 rpm and i had a few surges. what does anyone think gives? there are no audible leaks when hooked to a boost leak tester.

 

[91talon27]

I had the same problem last week. The car ran great no boost leaks. I found a exhaust leak at the O2 housing to downpipe. The gasket was toast. Replaced it and haven't been surging since. It was 3.00 at Advance Auto Parts.