Idle Issues

[Polygon]

So, I've got an idle issue that's cropped up recently. The cold idle seems to be fine. However, the warm idle is a little rough. It also will come close to stalling when turning the steering wheel when not moving at time.

Here's what's been done recently.

EGR Delete
New Intake Manifold
New Valve Cover
Plugs & Wires
New Y-Pipe
New Evo BOV
New Rear Turbo Inlet Seal
New PCV
New Booster Check Valve
Fixed Vac Leaks (Can't seem to find any more)
New Air Filter

So, does anyone have any ideas for what check next?

[Alex3000gt]

Excuse my ignorance of our modded turbo cars. Do you still have an IAC? On my NA this was not working properly and caused my car to studder under load - like when your power steering pump pressurizes the lines.

[Polygon]

Yep, mine is still on there. I've been wondering if I pissed something off on the TB when I changed the manifold. Maybe I'll trying pulling it off and cleaning it.

[Alex3000gt]

Yeah, cleaning mine with throttle cleaner did the trick. Also plug it in and see if it starts making noise when your car is on, the little motor in it should be moving. Mine also makes noise when the key is simply in the "ON" position, but who knows if yours will too.

[MaxClass]

When you removed the ERG system did you do the 10 ohm resister trick. It is my understanding that the connector that used to plug into the EGR valve needs to have a 10 ohm resistor fastened between the two wires on the old unused connector so that the ECU still thinks that the EGR valve is there.

Not sure what it does to let the ECU know but it should be done and it's easy enough.

[deemo99]

When you removed the ERG system did you do the 10 ohm resister trick. It is my understanding that the connector that used to plug into the EGR valve needs to have a 10 ohm resistor fastened between the two wires on the old unused connector so that the ECU still thinks that the EGR valve is there.

Not sure what it does to let the ECU know but it should be done and it's easy enough.

Hopefully someone else will chime in, but I thought the resistor was only to keep from getting a CEL? If this is for your 91 I don't know that the resistor is required. I removed my EGR on the 95, no resistor, no CEL.

[Atrosity]

Check your o2 Sensors? Hook a datalogger and see what it reads.

When turning the steering wheel the car will increase the fuel/rpm a little and it may stall out.

[blackrob]

I have a very similar problem. I thought it might be the EGR since the CEL gave me a code 43, but I replaced the solenoid to clear the light. The warm idle is still rough until I start going down the road. Any ideas anyone?

[Austin@STM]

Is the idle just a little low?

If thats the problem then try turning out you BISS screw a little to raise up the idle a little.

[Steve '92ES]

Couple thoughts:

1) Did you use an OEM PCV valve, and is it the correct one? Many of the aftermarket ones are either crap or incorrectly list the same valve for SOHC, DOHC, and TT. There are 3 different OEM parts for these. I've used Purolator on my NAs but OEM is the only way to go for turbo.

2) Ohm test your IAC as soon as possible. Do it twice, both stone cold and warm. A bad IAC can destroy your ECU so get that out of the way before moving on to anything else.

[Polygon]

Hopefully someone else will chime in, but I thought the resistor was only to keep from getting a CEL? If this is for your 91 I don't know that the resistor is required. I removed my EGR on the 95, no resistor, no CEL.

That is what I thought, in which case wouldn't be an issue for me (OBDI). As of yet I have not seen a CEL.


Check your o2 Sensors? Hook a datalogger and see what it reads.

When turning the steering wheel the car will increase the fuel/rpm a little and it may stall out.

I need to do that regardless. I should have gotten a data logger before I even got the car. It's under a cover right now. I'm going to be hooking a data logger up in the spring though.


Couple thoughts:

1) Did you use an OEM PCV valve, and is it the correct one? Many of the aftermarket ones are either crap or incorrectly list the same valve for SOHC, DOHC, and TT. There are 3 different OEM parts for these. I've used Purolator on my NAs but OEM is the only way to go for turbo.

2) Ohm test your IAC as soon as possible. Do it twice, both stone cold and warm. A bad IAC can destroy your ECU so get that out of the way before moving on to anything else.

It's an OEM PCV. As for the IAC, I bought a new one and I'm just going to replace it.

[Roybatty]

Subscribed. I have a similar low idle in closed loop and somewhat in open loop. +1 no cel for 1g Stealths for EGR delete. I have MMC palm logger and my IAC is trying to go above 120, which means adjusting the BISS counter clockwise a bit. Probably need to do the entire idle set procedure from manual. Will let you know if that makes a difference. My fuel and spark is good. Could this be the coolant temp sensor?

[blackrob]

Is the idle just a little low?

If thats the problem then try turning out you BISS screw a little to raise up the idle a little.
It is low, but it seems more like it's misfiring. I can rev it up and the missing goes away around 2K RPM's, but as soon as I let off the gas it acts like it's missing again. It only does it when the car is warm and not every time the car is warm. That is why it's so hard to track down.

I'll test the PCV and the IAC as soon as I get a chance. Any chance that it might be vacuum related?

[Polygon]

Oh yeah, definitely, check for vac leaks. They will cause all sorts of fun issues if you have any leaks.

[Roybatty]

Is the idle just a little low?

If thats the problem then try turning out you BISS screw a little to raise up the idle a little.

Backed out the BISS a little, but now when its been running, the ISC/IAC will bottom out at 0 and idle will be in mid 800 range.