infamous idle surge

[AlexSza]

Ive held off posting about this but now its just getting under my skin . After this build I kept finding little things that would set the idle off, but now after completely sealing EVERYTHING, (no boost leak, vac lines are perfect) it still manages to surge. It does not surge when I start the car, it idles high then drops after a few seconds. When i go to drive it, clutch in gas it and start to move, it will begin to surge but only between about 1,100 to 1,300 or 1,400 RPMS.

Is it okay to drive it with this surge, or will it cause problems down the road, the motor has only 11 miles on it, but about 5 hours of tweaking while running.

Could I drive it with the annoying surge until I can get the accessories for a tune


And another note, I have an aftermarket FPR, it works just fine but the barbs inside of the tapered ends are always cutting my lines... the lines are braided but there is NO way they are getting through the fittings that were provided, any help would be well appreciated.

i could maybe load a video off of my phone if it would help any!

 

[GSXSixteenG]

Check pcv, isc, and biss screw?

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

 

[LiquidX]

Check the IAC for burnt coils, check to see if your TPS is set properly and that the idle switch works. If the BISS was messed with you need to set that properly by grounding it the diagnostic pin.

All of this info is on the Vfaq.

 

[daplatano91]

I know my car started idle surging when my coolant temp sensor went bad. It would idle surge until the car warmed up then it'd be fine. A bit different then your situation but worth a shot.

 

[Chicken Patty]

The guide linked above should have everything you need to know my friend.

Now, having said that, if you want to take a shot in the dark,
Try closing your B.I.S.S. a bit and see if it helps. If not, time to start troubleshooting.

Keep us posted, best of luck bro.

 

[jongraack]

As stated above, check ## temp sensor and especially the idle air control sensor. Check the ohm reading of each and make sure the car is completely cool for proper reading from the idle sensor. Had this same problem with my friend's car after everything else was replaced. The temp sensor would mess up the idle after warming up for a few minutes but the idle sensor has a mind of its own, trust me. Sometimes it would drive fine but other times it would rev way up then drop and stall. If you have eratic readings from any of the tests done to your idle sensor then change it, IMO.

 

[AlexSza]

i already know about VFAQ, that is where i first started to try and fix it. The ISC motor is good, throttle body is well cleaned, the BISS screw could use a new o-ring (havent found anyone with the right size yet).
Replaced my temp sensors due to no hot start. RTV the UIC pipe to throttle body with gasket to the manifold.

The only thing i could think of is that the TPS is throwing a code, i have it set for 1.1 ohms at idle but wide open it only reaches about 4.7 ohms when its suppose to be near 5.6 ohms.

Summary: the throttle body and everything connected to it has been checked several times, but the TPS throwing a code and at 230$ for a new one and three others that tested bad, im running out of options besides the aggressive cams that are in the motor.

 

[Chicken Patty]

i already know about VFAQ, that is where i first started to try and fix it. The ISC motor is good, throttle body is well cleaned, the BISS screw could use a new o-ring (havent found anyone with the right size yet).
Replaced my temp sensors due to no hot start. RTV the UIC pipe to throttle body with gasket to the manifold.

The only thing i could think of is that the TPS is throwing a code, i have it set for 1.1 ohms at idle but wide open it only reaches about 4.7 ohms when its suppose to be near 5.6 ohms.

Summary: the throttle body and everything connected to it has been checked several times, but the TPS throwing a code and at 230$ for a new one and three others that tested bad, im running out of options besides the aggressive cams that are in the motor.

Extreme PSI and Street Tuned Motorsports both sell the o-ring for like $2-3.

What brand cams are you running?

 

[WIKDGSX619]

I been having the same issues for a while now and its sooo annoying,ive tried everything and cant seem to get it to stop surging,adjusting my afc seems to help sometimes but it doesnt rememdy the problem completely

 

[92AWDHX40]

Your cams arent stock, could be a problem there, seems after the build cams could be an issue how are you tuning your car. Do you have ecmlink?

 

[Calan]

Idle surge is almost always due to a mechanical problem; too much air is entering the engine during idle, which causes the ECU's idle feedback loop to start oscillating.

Look for any and all ways that air can enter the engine... eliminate the ones that shouldn't be there and calibrate the ones that should. Here are the most likely culprits in no particular order:

1. Thottle plate (idle switch/stop adjustment, varnish and carbon build-up preventing it from closing, etc)
2. TPS out of adjustment (TB plate is not where the ECU thinks it is)
3. Vac leak (lines, TB seals, etc)
4. BISS (out of adjustment, not sealing, etc)
5. ISC (motor malfunction, electrical connection)
6. FIAV (clogged or not closing)
7. Improperly adjusted throttle cable (keeping plate partially open)

The only thing i could think of is that the TPS is throwing a code, i have it set for 1.1 ohms at idle but wide open it only reaches about 4.7 ohms when its suppose to be near 5.6 ohms.

On the 4G63 motors (not sure which TPS the others use), the best way to adjust the TPS is by measuring the output voltage... not by it's resistance. Adjust it so that the ECU sees .63v when the throttle is closed.

It's also important that adjustments are made in the correct order. For example, on the 1G TBs you need to adjust the idle switch first, as this sets the mechanical stop for the throttle plate (which has very little room for error I might add). Only after this has been set should you adjust the TPS.

 

[AlexSza]

Idle surge is almost always due to a mechanical problem; too much air is entering the engine during idle, which causes the ECU's idle feedback loop to start oscillating.

Look for any and all ways that air can enter the engine... eliminate the ones that shouldn't be there and calibrate the ones that should. Here are the most likely culprits in no particular order:

1. TB plate (idle switch/stop adjustment, varnish and carbon build-up preventing it from closing, etc)
2. TPS out of adjustment (TB plate is not where the ECU thinks it is)
3. Vac leak (lines, TB seals, etc)
4. BISS (out of adjustment, not sealing, etc)
5. ISC (motor malfunction, electrical connection)
6. FIAV (clogged or not closing)



On the 4G63 motors (not sure which TPS the others use), the best way to adjust the TPS is by measuring the output voltage... not by it's resistance. Adjust it so that the ECU sees .63v when closed.

Yes i believe there is still air getting into the engine, i recently found out my valve cover had a crack in it and it gradually gotten bigger. Just polished and painted my new one and stuck that on looking for my book to find the torque specs for it. It had a pretty good 2 1/2 inch long crack by the cam gears.

as for the throffle body ive gone through four of them and chose the best looking one. everything from the air box to the TB is sealed right and tight, RTV where needed.

Im going to try this new valve cover and put a few clamps on hose fitting and see what happens. Ill locate my multimeter and run a few voltage tests on the TPS.

thank you!

 

[Calan]

Yes i believe there is still air getting into the engine, i recently found out my valve cover had a crack in it and it gradually gotten bigger.

Hate to break it to you, but the VC has nothing to do with air getting into the engine. About all a VC crack will do is leak oil or let crankcase gases (blowby) escape into the engine bay.

Did you actually test the intake and TB for leaks (BLT), or just go with what "looked good"?

 

[Boma]

+1 on daplatano's comment. I've owned 4 dsm's and 2 of them got bad temp sensors which fixed the problem. I've also dealt with the FIAV, ISC & the BISS. There's a guy here that works at RRE that had a TB mod that fixes the FIAV by screwing the freeze plug all the way in & shutting off the FIAV & I did that on 1 of my cars and a friend's car. It's almost like a mod by doing a FIAV blocking plate. Good luck.

 

[Chicken Patty]

+1 on daplatano's comment. I've owned 4 dsm's and 2 of them got bad temp sensors which fixed the problem. I've also dealt with the FIAV, ISC & the BISS. There's a guy here that works at RRE that had a TB mod that fixes the FIAV by screwing the freeze plug all the way in & shutting off the FIAV & I did that on 1 of my cars and a friend's car. It's almost like a mod by doing a FIAV blocking plate. Good luck.

I believe STM sells the block off plates, if he ever needs one.

 

[AlexSza]

Heres the strange part now.. After i swapped my uncracked valve cover over (didnt fix because stated above, just oil was getting through). I started the car, adjusted the CAS and BISS screw to idle around 1k rpms. I then started to push the car out of the garage, and it started to surge, this confuses me..

Any thoughts?

 

[Calan]

Heres the strange part now.. After i swapped my uncracked valve cover over (didnt fix because stated above, just oil was getting through). I started the car, adjusted the CAS and BISS screw to idle around 1k rpms. I then started to push the car out of the garage, and it started to surge, this confuses me..

Any thoughts?

My first thought is why were you able to adjust the idle, but then have to push the car out of the garage?

I'm guessing the car may not have been warmed up when you adjusted the idle. Once it hit operating temp and went into closed loop (about the time you pushed it outside ), the ECU started managing the idle and the surge started.

 

[AlexSza]

My first thought is why were you able to adjust the idle, but then have to push the car out of the garage?

I'm guessing the car may not have been warmed up when you adjusted the idle. Once it hit operating temp and went into closed loop (about the time you pushed it outside ), the ECU started managing the idle and the surge started.

had to adjust the idle after i switched valve covers. Surprisingly after about 3 miles of driving it stopped surging, which temp sensor could cause this? I replaced the main sensor to the ECU which caused my no hot start.

Another add is, when i start the car, it revs to about 2k RPMS, then drops to normal idling, 1k/900 RPMS. Is that pretty normal? EGR delete, vac lines are removed, AFPR,

Edit: i pushed the car out because it was only 10 feet, and I wanted to watch my fuel lines. They got cut twice due to me not knowing what the hell i was doing at first xd.

 

[Calan]

Not to be mean, but there are just so many things in your posts that make me go...

had to adjust the idle after i switched valve covers.

WTF

Surprisingly after about 3 miles of driving it stopped surging, which temp sensor could cause this?

WTF

i pushed the car out because it was only 10 feet and I wanted to watch my fuel lines.

WTF




***************

A temp sensor can cause lots of issues, but typical idle surge isn't usually one of them. Not that it can't happen, but idle surge issues are usually due to a mechanical problem that is screwing up low-speed airflow, as mentioned above.

The one exception that I can think of is if the ECU is switching between open and closed loop at inappropriate times due to a bad coolant temp sensor. In that case, idle surge could increase or decrease depending on what the ECU is attempting to do.

 

[AlexSza]

oh ok thanks..., well i dont have AC so that really only leaves 1 other temp sensor correct.

 

[92AWDHX40]

Did you do a boost leak test yet?