Help! 92 idle has me tearing my hair out!

[Gnawzzy]

This car is doing bizarre things that have me going crazy. Maybe someone can point me to the next step

Symptoms: car exhibits intermitent behaviors on startup. i can start, turn off, and restart the car several times in a row and it will do any number of the following things in random order each time:

1) Super high idle and rich exhaust smell. runs and drives fine, but idles around 1800 in park.

2) No idle: will fire and run fine if I hold the accelerator down just a touch to maintain some revs, once I let the pedal go for even a second the revs fall below 300 and the car dies.

3) Completly normal and perfect operation, perfect idle, perfect driveability, everything.

I'm compelled to repeat it will do any one of these things between turning the car off and starting it again immediately, there appears to be no rhyme or reason to any one of these behaviors.

Engine codes: none!

What I've already replace: IAC, TPS, Fuel filter, fuel injectors.

What I'm thinking: Computer, Optispark, or plugs and wires, maybe EGR?

ive gotten to the point where the next things I have to start replacing arent super cheap or easy like the other stuff, ao I was hoping based on this info or any I could provide if you fine folks could give me an idea of which is the most likely to be causing this schizophrenic ossiclation between high idle, no idle, and running perfectly. every time I turn the key it's a crapshoot what it will do.

thanks!

 

[DonB]

I'd check the obvious, timing, vacuum leak? How many inches of vacuum is it pulling?

If it's NOT pulling a code it probably isn't the computer or anything it reads or controls. Although EGR's are a bear to work on and will wreak havoc. They will cause the symptoms you are describing. They carbon up and don't seal properly or the valve in it just burns up. I did my injectors last year and while I had it down, I put a new EGR in there just to be sure.

Are you using a FSM? The troubleshooting is invaluable. Especially with an Opti. Otherwise you are just guessing, and that gets mighty expensive.
.

 

[Hib Halverson]

Some questions and one suggestion

1) Does the check engine light come on then go out during "bulb check".

2) What testing device did you use to determine there are no ECM codes set?

Jack the front end up. get under the car and look for the big-assed bolt screwed into the block above the oil filter. There will be a lot of black wires connected to it. Remove the bolt, clean all the cable connectors. Clean the surface on the block. Clean the bottom of the bolt or washer which hold all the connectors.

Tighten that bolt to spec then road test and report back.

 

[Tom G]

Replace Opti spark

Sounds similar to my 92. Did you replace Opti spark.
See below

I have a 92 that I had taken to a dealer because you could not keep it running. After them spending a great deal of time to determine the problem they said I needed to replace the optispark and of course the water pump. I had it towed home for I did not want to spend the $2000 they said it would cost. Asked my local mechanic if he would do it and he said no for he had done one once before and said he would never do another. When I asked him why, he said that he spent so much time trying to get it set right he would not do it again. My question is doesn't the optispark just fit on one way and therefore doesn't need timing. I have seen the forums on how much needs to be removed but am concerned about getting the replacement properly installed. Any guidance would be appreciated.
Thanks
Tom

 

[Wayback]

optispark ignition info | Grumpys Performance Garage
A good guide ,it doesn't seem too involved,looks like the hardest part is removing the damper.I did a lot of research since this is my 1st Opti also.While your at it ya might as well change the wires,hoses,termostat etc.with the opti removed get a bottle of spray Gunk & clean the radiator&AC condenser front & back,let the gunk sit for awile then spray it down with a garden hose.

 

[Wayback]

sorry,double post. but heres a link to a opti replacement. seen some info where the MSD's & Duralast etc basically suck,this got some good reviews & fedback.
LT1/SBC

 

[Tom G]

sorry,double post. but heres a link to a opti replacement. seen some info where the MSD's & Duralast etc basically suck,this got some good reviews & fedback.
LT1/SBC

Thank you looks like good info. Have you actually changed your opti spark?

 

[Wayback]

Thank you looks like good info. Have you actually changed your opti spark?

No Tom I havent,but if ya read on how to do it, it's not that involved.I wouldn't think twice to R&R a opti.

 

[Tom G]

No Tom I havent,but if ya read on how to do it, it's not that involved.I wouldn't think twice to R&R a opti.

That is what I thought but when my local mechanic said he would never do one again for he had difficultly getting it set. I under stand there is just one way to install it lining up the notches on the shafts. Is that your understanding?
Thanks for you time and imput

 

[Wayback]

Heres a good VID on it,plenty more on u -tube also,Looking thru GRUMPYVETTES/ PAUL'S LINK is good also,its keyed so it's only gona go in 1 way.
YouTube
I did all the hoses on my 93 this summer & the tb bypass,if ya jack up the car & remove both front tires it's a lot easier to work on the motor,easier to get to the rad petcock also. Be sure to put stands under it also,my driveway is crushed stone i put 6x6;s under the Aframe etc. I work nights so my time on here varies. If you were closer I would give you a hand.

 

[Tom G]

a

Heres a good VID on it,plenty more on u -tube also,Looking thru GRUMPYVETTES/ PAUL'S LINK is good also,its keyed so it's only gona go in 1 way.
YouTube
I did all the hoses on my 93 this summer & the tb bypass,if ya jack up the car & remove both front tires it's a lot easier to work on the motor,easier to get to the rad petcock also. Be sure to put stands under it also,my driveway is crushed stone i put 6x6;s under the Aframe etc. I work nights so my time on here varies. If you were closer I would give you a hand.

Wayback, thank you. I am new to this but I have a classic car friend who will help me. You have encouraged me that I should be able to do it. The video you forwarded is good, thanks again for your help and time.

 

[Wayback]

Your more than welcome Tom.Im glad your gona do it & your friend is gona help.Just take your time & you will do fine. The more you can do yourself the more $ you can save.Back in the day we only had a "Motors Manual " for reference. When ya finish ,let us know how ya made out.As the old sayen goes "Nothing ventured-Nothing gained"