My 87' since i got it has always revved up and down when it is cold and has had a sporadic idle once hot (sometimes idles at 700, sometimes 1100) I took apart the idle air control and cleaned it real good and it seems better but the problem it still there, any ideas?
Thanks!
Ben


[Modified by belmor, 7:34 PM 12/20/2003]

 

Check tech tips on setting base idle, check timing, wires and plugs... and just replaced by ESC with updated one and that helped after setting base idle... :thumbs: :thumbs:

 

I have a "Word" procedure (different than on tech section) on setting the base idle. The steps come directly from the 89 GM Hemls service manual. Let me know it you want me to send this to you on email. Happy Holidays!

 

I would like the info please :thumbs:
Dankai@shaw.ca
:cheers:

 

i had a similar problem with my 94....i replaced the stock coil with a msd blaster coil car had 68k on it. this fixed my problem...only when the car became hot i had the problem

 

Please shoot the info too me about setting idle, As ive driving it since i cleaned the IAC it is better, but still doing it when its real cold, I think a full tune up is in order
Ben

ben6119@yahoo.com

 

You might also clean the TB and check for any vacuum leaks. Also verify that the IAC connector is tight and clean.

Indeed set base idle and TPS at base idle, my method is on my site (link in sig. below).

 

Don't know how helpful this is but...

On my '87, I think it's all in the combo settings of the base timing, TPS and idle speed, even fuel pressure and how clean everything is including the IAC and TB. One setting works with the other.

I have everything ported from the heads on up in the intake but nothing radical. The idle was always a little rough at the stock settings but steady and acceptable otherwise. Then I added a 52mm throttle-body and I had to learn all new settings.

With no other changes and the stock settings, the 52mm TB made the car REALLY idle rough, up and down idle, a serious off-idle stumble and lots of backfiring to the point of undriveable.
Then I read somewhere here about a member who ran 7.2V-7.6V on TPS setting instead of the stock 5.4V. I tried it. And man.....what a difference!!!

The engine idles smoother than it ever has with that cam, comes off idle without hesitation and the backfiring is totally gone.

Right now I'm running 8 degrees base timing and 7.4V on the TPS. I'll be testing lower timing settings in a few days as soon as I get over this dang flu bug. There's buzz now about lower timing making more HP and more driveable. I have to check it out.

Again, make sure everything is clean and follow the proper procedure for setting the TPS (and idle speed) even if the voltage is different than stock.

Good Luck,
BIG JIM

 

You might check for worn bushings on the end of the throttle plate shaft. If there worn excessively the shaft will be moving around enough that the TPS becomes involved. ...sending a message for some fuel to the ECM and therefore the idle raises.... and the cycle repeats. Just a thought.

 

Email sent on the base idle set procedure. As requested, Sam

 

You might need to rebuild or replace your throttle body. Mine dometimes does the same thing, but my linkage sometimes sticks. Just another thought.