:bb Im a friggen idiot. :crazy: Thanks

 

I can't get the idle to stay up. I have followed the instuctions listed on page one, but the idle won't stay up.


[Modified by vettes rule, 4:59 PM 5/28/2002]

 

Mine started doing the same thing the other night as I was trying to
run against a Z28. I had to break off because the car started to stumble.
Make 'A'.
Anyway, changed the fuel filter, seems like problem got worse. Plugs looked
ok. Changed distributor cap and rotor, then had to quit to go to work.
Will continue with cap and checking plug wires tomorrow. Will also get a new IAC as was mentioned in this post. Thanks for everyones help with this problem that almost everyone runs into.
:cheers: :) :seeya

 

Best bet is to try the plug wires. My boss' Intrepid had an intermitant stumbling problem, which turned out to be a tiny pin-hole in one of his spark plug wires. Almost invisible to the naked eye. Easiest way to check would be to pull the car into the garage, bring the garage door half way down (but don't close it!), turn-off the lights, and fire the car up. Lift the hood and look for any stray sparks (a little flash of blue-white light). If you see that, then you've solved the stumbling issue - just don't leave the car idling in an almost closed garage too long...can you say, "carbon-monoxide poisoning"?

Of course, for the $60 that a new set of wires will cost, you might just be better off changing them without doing the test...what have you got to loose?

As for the stalling out and weird idle, it sounds like a problem my dad's Oldmobile had a few years back. We changed every stinkin' sensor on that car to find the problem, when all it turned out to be was a bad ECU (engine computer)! And the GM dealer had a REALLY scientific test to determine it too: They lowered the ECU onto the passenger floor (In my dad's car it's stored under the dash on the passenger's side; on your '91 it's under the hood I think), fired the car up, then tapped on the computer. The engine died instantly! Real hard-core diagnostics at work here, huh? $1400 in brand new GM sensors to find it was a faulty $200 computer!

In fact, MidAmerica Designs sells remanufactured ECUs for like $100. At that price, it's worth buying one just to have as a spare for situations like this. Again, for the price what have you got to loose?

It's been said before - start with the simple stuff first.

Good luck with the car.

P.S. Just in case nobody's mentioned it to you - DON'T TRY TO ADJUST THE IDLE USING THE IDLE AIR SCREW ON THE THROTTLE BODY!!! There's a BIG sticker on the rad support stating that it's been sealed at the factory and NEVER needs adjustment. I've seen people break the seal and try to set their idle using this adjustment screw. DON'T DO IT! It will only lead to more headaches...

 

Have you done a tune up. Plug wires can burn rather easily on the vette and will cause it to miss very bad. I have had this happen many times (modded motor)

Any idea where the timing is set? Timing effects the idle, the higher the timing, the higher the idle will move up.

Are you following the instructions for resetting the IAC to the "T" as they say?

I had a recent problem on my super ram ('90), the car stopped ideling after an 80 mile drive, I had to rev it to keep it running. I found that thr runners were loose. this is air that is not being metered by the MAP sensor. And it showed on my instant MPG, in 5th gear I was coasting AT 55MPH and getting 10 MPG. So vacuum leaks are another source to look.

When you do get it to run, does it run okay when you go to full throttle?
Have you checked your voltage at the TPS sensor? Mine got wet and screwed up my idle. It was at 4 volts at idle. should be at .54-58

 

Are you hearing any hissing sound when it's idling? If so you may have a leak in the coil. Also, whoever said check the simple s*** first up here is right. Check to make sure firstly.......and I know this sounds stupid, that you spark plugs cap settings are at what they should be and not too high. The dumbf*** changed them on mine when I bought it and even slightly higher they f*** everything up. The idle would run very low and then it would race up when you gun it, but it would stall every now and then. I think your settings should be at 0.035 like mine unless it's a ZR-1. Also, make sure your TPI is cleaned out correctly and make sure your filters are clean and changed. Any other reasons would probably be your IAC settings or your throttle is offset. It's probably one of these that's affecting your idle since it sounds bad..........but I bet, from what you described.............it's your cap settings. Make sure they're set correctly.....on an L98 that sh** makes a MONSTROUS difference. I went through so much s*** with mine you wouldn't believe. :cool: Oh yeah.................and use Platinum plugs man. The post above me reminded me of it. The dumbf*** checy distributors put cheap s*** in there purposely and if your cap settings are set wrong on an L98 that shiz is probably burned to a crisp by now on your L98 unless they're plat.


[Modified by MaSTeRofDZaSTeR, 11:19 AM 6/1/2002]