Idle problem -- Still

[Blt4ice]

Ok here is the updated situation

Problem: Rough idle, tends to idle high around 900-1000rpm, when it settles down at 750 rpm in Drive the vehicle tends to bounce. When accelerating gently from a stand still, say 1/4 to 1/2 depress on pedal, the car sounds like it is loading up and loses power. The faster the rpms the better the car feels. I know bad excuse to get on it. It almost seems as the car is running too rich at idle.

Repairs: Plugs, Cap, Rotor, PCV, Fuel Filter, Oil/oil Filter, TPS sensor, Sprayed out Throttle body, Fuel additive to remove possible water in fuel, Full tank of 93 Octane gas. After all the above still the same problem, only a slight change in that the "stumbling" at a stand still when idle hits 750rpms is less dramatic (my head doesn't hit the glasstop anymore) but it still bounces pretty good.

Any suggestions as to what I should look at next? I am really at a loss and not to mention losing cash, fortunately I did not throw any of the old parts away as they are probably still good, and will make for a decent replacement if in a jam.

Thanks in advance.

Brian

 

[Rogue]

Your description of the problem is exactly what happened to my 'Vette not too long ago. The idle was erratic; it went up and down. When I put it in gear, the idle would go low and occassionally want to die. When I stepped on the gas, the car would hesitate slightly then "jump" off the line. Then at part throttle, it was very jerky. However, as soon as the revs rose and I was cruising at medium to high speed, the problem seemed to disappear.

Diagnosis: Bad fuel injector in one cylinder. I replaced that injector and problem went away. But after a couple of months, came right back. Another bad injector in another cyclinder.

Since it cost $300 in labor to replace one injector, or all injectors, I just replaced ALL injectors and paid that one $300 labor fee. Each injector from GM was $139. You do the math. OUCH! You can get injectors for a lot less through Mid America and Ecklers. I believe you can get all 8 for $300. If this turns out to be your problem, I'd just replace all 8 injectors via the 'net or catalog and pay the one time labor fee of $300. You'll save money. Or do the labor yourself. Sorry. Not exactly what you wanted to hear.

 

[Blt4ice]

Anyone know a way to test the injectors at home? Without hooking them up to the pressure machine?

 

[livinez]

Similar problems here.

I used a mechanics stethiscope to find a injector problem after rebuilding my 85. It was a bad injector connector. Cut the old lead off and replaced it with a replacement found at most auto parts stores. I also had to replace my IAC valve as mine was froze. But yours appears to operate properly.

You might try using chemtools injector cleaning kit. Other wise it sounds like it might be time to send your injectors to Gordon at Witchhunter to get cleaned and flowed. Mine ended up shot after previous owner let the car sit for 3 years! But Gordon cut me a great deal on a flowed used set he had!!!
Sure sounds like its a injector.

 

[Cruise]

I am not sure if your issues were as bad as mine, but here goes:

My '94 had:
High and rough idle, no kick down passing gear, ASR service light stayed on and SYS kept flashing.
After replacing the battery, TPS, ECM computer it still didn't help.

It turned out to be the A/C wiring control module that was corroded.
I couldn't believe that one connection affected the car that badly, but the cars problems all went away as soon as GM installed a new connector.
The worse part, was the trouble codes were not showing the wiring connector. My mechanic found it by accident, out of frustration.

If you have any of the above symptons it might be worth a look.

 

[WhalePirot]

I got fabulous prices on the Bosch set at:
TPI Tech (860)599-0382
9 Canterbury Ln
Pawcatuck,CT

Whilst not GM brand, they are fine, and were a LOT cheaper.

 

[Hyde]

Make sure your TPS is properly adjusted. .54v at idle (+/- .075v).
Check base timing. I believe 6 deg BTDC.

MAF. Disconnect MAF, be sure to keep wire from touching belt, and start car. If consition changes, prob. MAF. Turn off ignition before reconnecting.

Good luck.