Cold start idle problem

[Murphy3081]

Hey everyone, I have an 87 GN. Lately in the cold weather its been having problems on a cold start idleing. On a cold start it revs high then goes low then back to high then low etc. It often idles so low that it stalls out. Once the engine is warmed up in a couple minutes the engine runs normal and starts up normal as well. During cold starts I have to keep my foot on the gas untill it warms up a little to keep a smooth idle with out it stalling. The MAS is good and the IAC valve is new. Any ideas for a solution would be much appreciated, thanks.

 

[TurboRegal84]

Is the IAC valve set correctly? Do you have a scantool? If you do what are the IAC numbers?

 

[1quick6]

As mentioned, you might want to read this:
IAC Reset Procedure

It might be new, but it still may need to be set to spec.

 

[bmackinnon]

What chip?

 

[Murphy3081]

hey everyone sorry for the late response. i used the reset procedure and reset the IAC. the numbers are all correct. i noticed it now has a smoother idle. however on a cold start it is now running smooth for about a minute then just stalls out unless i keep my foot on the gas. vacum leak maybe, wiring, i also read somewhere a fuel injector problem?????

 

[frdstang93]

I had a similar issue and found it to be the TPS was bad.

 

[TurboBuRick]

Could very well have a vacuum leak but it sounds like the iac or tps is still out of wack.

How did you set them? Whats the iac number warm at idle?

 

[bmackinnon]

What chip?

Again..... what chip are you running? If it's the stock chip, they are notorious for doing exactly as you explain... idle hunting and dying a couple times after cold start....

 

[mikestertwo]

A bad O2 sensor will do that also.

 

[TurboBuRick]

A bad O2 sensor will do that also.

Not to say your wrong but the o2 sensor does not come into play until the motor is warm and the ecm is in closed loop.

 

[mikestertwo]

i noticed it now has a smoother idle. however on a cold start it is now running smooth for about a minute then just stalls out unless i keep my foot on the gas.

It idles smooth then stalls. It only takes a minute or two to go into closed loop. I had this exact same symptom on my 87' and it turned out to be a bad O2 sensor.

 

[Murphy3081]

ok thanks for the input. i am going to look into all of this. i am running with the stock chip. is there any way to know when they are going bad besides the messed up idle-stalling.

 

[bmackinnon]

ok thanks for the input. i am going to look into all of this. i am running with the stock chip. is there any way to know when they are going bad besides the messed up idle-stalling.

Stock chip... I knew it! lol....Then your car is running normal... assuming, like you said, that the iac and tps are set correctly, and the numbers are right.... the chip isn't going/doesn't go 'bad'.... it was just a fairly crappy calibration from the factory... My car ALWAYS died at least once in the morning when it had the stock chip, since brand new.... everyone's did.... do yourself a favor, and order a chip from TurboTweak.com, and believe me, your car will idle, run, drive like you never, ever thought it could.... night and day difference, for real! Best, what, $75?, you ever spent....

 

[Murphy3081]

hahaha yeah im going to def check that out, i ve been holding out to look for a new chip but this put me over the edge. i didnt realize they were that cheap. i need to gather all the numbers/info together

 

[KL Mallender]

Try grounding ALDL connector, then unplug IAC motor(with key on, engine off for a minute),start engine, adjust idle to 600-700 rpm, reconnect IAC, clear any codes then adjust TPS to .46-.52
As I remember that worked well. good luck.

Kevin.

 

[Murphy3081]

i did that when i reset the IAC. i did notice a more smooth idle but still on a cold start it stalls after about a minute.

 

[KL Mallender]

Yeah, like Brian mentioned earlier, stockers were a little "cold-blooded", if your good on all adjustments, might be the time to "Update' the software, lots of improvements in 20+ years, I am completely out of date with all the Mass-Air combos but the real braintrust is in one of these rooms, lol :biggrin:
Good luck.

Kevin.

 

[mikestertwo]

The stock chips went into closed loop pretty early...I think around 89 degrees which made them pretty cold blooded. Definitely get one of Eric's TT chips. That's why if your O2 sensor isn't up to snuff it will stall when cold.

 

[Murphy3081]

im getting a new chip and we will see how that goes, ill let you all know. thanks for everything.

 

[Murphy3081]

Hey everyone im sorry for the delayed response. I got a new chip and put it in. It now runs awesome, no more stalling, better than before. Thank you for all your assistance!!!