Bad Idle

[1RIPPEN6]

87 t will idle fine for the first 30 seconds and then shuts off. If it decides to idle after that it will hunt real bad and then shout off again. It does this any time after setting for more than 4 hours. Once the car is warm it will idle fine.
Set tps .44, cleaned throttle body and iac and iac reading 26 warm, switch MAF no change, switched iac no change. Did gnttype.org spring clean no change. Car is stock except for rjc plate, percision plenum, and adjustable fuel regulator(paper with regulator read 42 psi with hose off idling is this to much for stock injectors). I put this stuff on while trying to trace idling problem. It did not idle before I put the stuff on. I want to do more but I want to fix the idle problem first so what should be the next step in fixing the idle problem. Thanks in advance

 

[mikestertwo]

How old is your O2 sensor?

 

[1RIPPEN6]

I read on gnttype.org that the one from the gnx worked better so I put one in three months ago did not help

 

[86 TR]

possibly bad coolant temp. sensor??

 

[1RIPPEN6]

Sorry i guess i changed more stuff than i could remember. How many coolant sensor are there. My understand is two, one for the computer and one for the warning light. I tried to get both but the auto parts only listed one. The one on the ds front of the intake manifold.

 

[Hafrod]

What chip do you have?

 

[1RIPPEN6]

Stock chip

 

[diomedes]

Not trying to hijack the thread but my GN just started the same show you described. Once its all warmed up it starts and idles fine. But when shes cold or has been sitting, the idle picks up pretty high then slowly comes down and till it shuts off. Only once the car is warm does it straighten out.

Dunno what it is but am excited to find out, so i can solve it.

 

[1RIPPEN6]

Jump aboard I hope we can solve the problem. My 86 did the same thing I sold it that way. The boy who bought it rebuilt the engine and it idled after that.

 

[diomedes]

A Rebuild
Guess not to many people know of our dilemma.
Not the MAF (which I was thinking of replacing it, even though it passed the "tap test")
Have already replaced all vacuum lines (I think)
Next was the PCV
I was about to start shooting in the dark till I get it.

 

[1RIPPEN6]

I have already replaced my PVC(GM) and most of my vacuum lines that even looked questionable and it did not help

 

[jcawley3]

me too

I'm having the same problem but mine is not shutting off but almost.....I was told on gnttype board to change or clean the IAC so as soon I a find out what that is...I going to clean It!!!!!...I keep you posted!

 

[diomedes]

at first mine would not shut off, just idle roughly then rev up again.
Just recently did it start turning off completely.

Honestly Im starting to think this is a "junior member" curse only.
hahaha

 

[asd60303]

my gn does this also, I hope someone on these boards can help us.

 

[SouthernCal GN]

Reset the IAC, and make sure the TPS is within spec;

gnttype.org- look for the article on 'spring cleaning'

 

[mikestertwo]

My experience with this problem has been either a bad O2 sensor, vacuum leak (in one case a leak between the dog house and the manifold), misadjusted IAC, or adjusting an IAC to compensate for a vacuum leak. The latter case, the IAC was set to 20 cts, looked normal. Discovered a vacuum leak, repaired the leak, IAC's went to "0". Reset IAC back to 20"s, problem gone.

 

[1RIPPEN6]

the car was not idling so I did remove the heads for a valve job because the boy that bought my old car rebuilding it and then it would idle. Hoping that a bad valve was the problem it was not. My next step is swapping out the ecu and then a compression test. I did get another set of stock injectors today so they will probably be swapped before the compression test. Will let you know how I make out.

 

[1RIPPEN6]

Quick update I replaced the injectors on Sunday and the car is idling now. It is not perfect but very close.

 

[WIKEDV6]

You can also get a better chip that can cure a lot of the idle problems you have with a stock chip. 20 yrs is a long time and a lot of chip gurus have figured out how to tweak everything. I remember back in the days just going to Pittbull chip made the motor run a lot smoother on idle.

HTH

Prasad

 

[BuickMike231]

This problem has happened to my car twice so far, the first time I swapped in a new MAF sensor and it was fine. The 2nd time was the other day, it did it again, I got it going without really knowing what was wrong (didn't actually do anything on my part) and it hasn't done it since. I would love to know what actually caused it too!