I've got a 1988 with a high idle problem, usually runs at about 1400 rpm at idle. it will drive for a bit but then it will stutter and fall flat on it's face when you give it gas. it will act like it is flooded and backfire through the intake. once in a while it will throw the EGR system code.
once in a while it will start up and idle at about 750 for a few minutes, rev and drive good, but then the idle will kick up to 1400 and act up again. I haven't found any vacuum leaks, doesn't mean there aren't any. I've replaced most of the vacuum tubing and the EGR valve. next step was going to be the EGR solenoid but I cant seem to find any available.

Any ideas you could throw at me would be greatly appreciated. had the car for about a year and cant drive it. getting frustrated.

thanks in advance'
Chris

 

look for vacumm leaks and have you ever replaced your 02 (s) sensor (s) and give your throttle body a good cleaning. and your idle control valve.

 

haven't replaced the O2 sensor yet, Ill have to look into that. cleaned the throttle body and replaced all the throttle body gaskets., thanks for the input. Ill keep looking for vacuum leaks.

 

did you use blue locktight on the bolts and clean the idle control valve?

sorry iac idle air control

 

yes, blue Loctite, I cleaned and adjusted the IAC valve per the FSM, but I am still thinking may want to replace the IAC valve.

 

big range on them $10 to $60 make sure the connections are good.

 

thanks for your help. I am hoping to make some progress this weekend.

 

Wow, I am having the [B]exact[B] same problem with my 88 and have replace most of the vacuum lines also. I have also cleaned the throttle body and IAC to no avail. I also get the code once in awhile. I have not looked at he EGR valve itself yet, and that will probably be my next job, but I rarely have time to mess with it. I will definitely be paying close attention to this thread, and please post your resolution if/when that happens & I will do the same. Forgot to ask, did you check with MidAmerica for the EGR solenoid ?

David

 

If it only runs bad at idle, I would suspect the IAC (Idle Air Control).

If it runs bad when driving down the road, I would suspect egr valve or timing is off. Your distributor could be turning due to the lock down bolt being loose.

 

Thanks for all the info so far guys. Didn't get a chance to look at it this weekend, as soon as I do I will keep you posted.

 

My Pontiac Grand Am had a lot of those symptoms when my Mass Air Flow sensor went bad.

 

Any update on your problem/resolution ? I had to put mine away for the Winter season here in MN now so I won't get a chance to mess with it for a while. Keep us informed, thanks much.

David

 

Sorry for the delay folks, We had a death in the family. So far I have replaced the IAC valve and it didn't seem to make any change. I next replaced the TPS, and it did nothing either. Other items that have been replaced over the last several months are EGR valve, Fuel Pressure Regulator, Fuel Pump, Fuel Filter Coolant temp Switch. I want to replace the EGR control solenoid, but no one seems to stock it. I have been told by a mechanic friend to replace or have the ECU checked. That may be my next step.

Happy Holidays and I will keep you posted, getting to cold to do much to it plus the snow is coming soon I am sure.

Chris

 

You can't change or replace the Tps sensor without doing a minimum Idle adjustment. If you haven't done it I would recommend. I would do this after you have checked vacume lined and brake booster connection. Then disconnect the battery and clear codes. After that if you get a code for something clean and grease(dielectric) the connector for that system, after that mabey defective part. Make sure wires aren't touching due to shrinking coating.
Good luck


Tools & Equipment

You will need the following tools and equipment:

1. A set of Torx wrenches. You can buy a complete set in a nice, genuine plastic pouch at Sears.

2. A good digital voltmeter that will read voltages less than 1 volt.

3. A paper clip.

4. A small screwdriver.



Procedure

There are two electrical components on the TB that you will be working with: The TPS and the Idle Air Control Valve (IAC). Make sure that the connectors for these two components are easily accessible and that you can easily disconnect the IAC.

You will also be playing with the diagnostic connector under the dash. Remove the cover (if it’s still in place). Bend your paper clip into a "U" shape. You will be playing with the two top right hand terminals ("A" and "B") in the connector.

First step is to set the minimum idle speed. If nobody has messed with this on your car before, the set screw will be covered by a pressed-in plug. It’s located on the driver’s side of the TB. Remove this plug if it’s there.

With the IAC connected and the ignition "OFF," stick the paper clip into the diagnostic connector from "A" to "B." This grounds the diagnostic lead.

Turn the ignition to the "ON" position without starting the engine. Wait 30 seconds.

Now, with the ignition still in the "ON" position, disconnect the IAC connector at the IAC.

Remove the paper clip from the diagnostic connector.

Start the engine and allow it to reach normal operating temperature. The idle speed will probably be really low, and you may have to coax the engine a bit with the gas pedal to keep it running for a while.

If your car is an automatic, set the parking brake and put the transmission in "DRIVE." If your car is a manual, leave it in neutral.

Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.

Shut off the engine and re-connect the IAC.

That’s it for idle speed. Now on to the TPS.

There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires. You can either buy a special harness connector that breaks these wires out (from Mid America), or gently pierce the insulation of the wires with the pointy prongs on your volt meter. You can also stick a paper clip into each of the two top locations of the connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.

Turn the ignition to the "ON" position without starting the engine.

Loosen the TPS Torx (phillips)adjustment screws.

Set your volt meter to a low scale DC volt setting that will accurately read less than 1 volt.

Measure the voltage between the two top TPS wires.

Adjust the TPS by rotating its position until you get a reading of .54 volts.

Tighten the Torx screws and recheck the voltage. Re-adjust if necessary to make sure voltage is right at .54.

Turn the ignition "OFF."

You are now in perfect adjustment on idle speed and TPS output. Start the engine. It may take a few seconds for the car to "catch on" to its new settings.

 

So, After following the procedure laid out by xrav22 above, thanks again by the way. I managed to bring the car closer to where it should be but within minutes it went right back to where it was before. so I decided to go ahead and replace the ECU since I already had one. I disconnected the battery and replaced the ECU then again performed the idle procedure and now the car is running perfect, put about 100 miles on it so far. Thanks again to everyone for the help.

Chris

 

Car is still running great, I replaced the brake booster last night and learned one thing. I am too fat to be calling around under the dash of my C-4.
Thanks again everyone for the help.

Chris

 

Glad to hear it's still running great. I will definitely look into replacing my ECU come Spring and hopefully that will take care of my problem, since it sounds exactly like what you had going on. Thanks again for the post.

David

 

So, I finally got a chance to work on my 88 and replace the ECU. Very happy to say that it took care of my high idle problem too. Thanks much Cheerless for the info and this thread, it saved a lot of headache and money. My only problem now is it seems to sputter/miss on acceleration, but only before it warms up, then it seems to run good. Oh well, one problem solved, and one to go. Thanks again, Cheerless.

David