Idle still searching. Any ideas?

[87blackroxi]

Previously the idle was searching horribly bad to the point of stalling out When at idle. Well, gapping the new plugs corrected that. But it is still searching a little at idle between 6-700 rpms.
Last month I changed the plugs, wires, distributor cap and rotor. Do you think I need a new coil? Maybe a high performance one? Cause I am thinking it is probably the original.

 

[wishuwerehere82]

Try recalibrating your TPS. It is usually the cause of idle hunting/surging. Make sure you look for all possible sources of vacuum leaks too.

 

[Mr Dark]

If I remember correctly, I read in a book called "101 Projects for your Corvette" that this problem could be caused by a dirty intake. It's been a while since I read it, but they said that dirt on the plates causes them to not close completely and that forces the idle to keep "searching". They said to remove the black plastic hose that connects to the intake and see if the plates looked dirty. If it looked bad, they said that you might have to remove the entire unit and clean it (carefully). I'm sorry I'm vague, but I just don't remember all of what they said. Good luck...

 

[Moonunit 451]

Try recalibrating your TPS. It is usually the cause of idle hunting/surging. Make sure you look for all possible sources of vacuum leaks too.

Sounds right to me as well. Are you throwing any codes. Might also consider the MAF, and the o2 sensor.

 

[87blackroxi]

Sounds right to me as well. Are you throwing any codes. Might also consider the MAF, and the o2 sensor.

No codes. And it's a new o2 sensor. but I might have to take a look and see if it's dirty.
What about the ignition coil? Should that be replaced as well?

 

[Moonunit 451]

I don't think the coils need to be replced as a matter of course, and they're expensive. I'm not sure about testing them. Was this all happening before you did the tune? If not, I'd be thinking vacuum leak from something you may have inavertantly messed up.

It'd be nice to get an OBD 1 scan, could save you a lot of time and trouble, and shouldn't cost much.

 

[87blackroxi]

I don't think the coils need to be replced as a matter of course, and they're expensive. I'm not sure about testing them. Was this all happening before you did the tune? If not, I'd be thinking vacuum leak from something you may have inavertantly messed up.

It'd be nice to get an OBD 1 scan, could save you a lot of time and trouble, and shouldn't cost much.

It was idling fine before the tune up. Then plugs, wires, distributor and cap and horrible idling. I gapped the plugs properly and it idled good. Now it is searching a little. rechecked the gaps and they're good. Y'all think It's a good idea to clean the tpis? And is it a diy project?

 

[Moonunit 451]

You mean the TPS?

 

[87blackroxi]

You mean the TPS?

exactly!

 

[wishuwerehere82]

You can't clean it. It's a sealed unit.

 

[Hib Halverson]

First, I'd get a factory service manual. Next, I'd read the subsection in the section on intermittants about unstable or rough idle. Follow those instructions to diagnose the problem.

Potential problem areas are the IAC, TPS and the TB itself. Pull of your air duct, open the throttle wide and look in there with a flashlite. If you see a lot of black icky stuff around the bores and the plates, take the TB off and clean it. Verify the IAC and TPS are working properly...repair as necessary.

Does this engine have any codes set?

 

[87blackroxi]

codes. not that I know of. I don't have a scanner.
But I will try this weekend to take a look at the tb, and iac

 

[Moonunit 451]

Hib's info is always good. Now I'm gonna throw out a couple into left field. I don't see that you have replaced or checked your air filter

Now this one is way out there.

There are two relays down behind the battery. They are the main burn, and burnoff relays for the MAF. I have been told that they are the same part and part # however mine are not. They are bolted, or riveted to the firewall on my 86. A mechanic friend of mine recently fixed an idle problm on an 88 and says that both need to be replaced at the same time. Around $15 @. This car was throwing a MAF code and a new MAF did not fix the problem. He called some genious buddy in Alaska who tiped him off on this, he didn't find it in the trouble shooting schematics :confused

You can pull codes without a scanner using a paper clip. Try a search for the proceedure. The reason I suggested a scan is that it might pinpoint something quickly.

 

[vetteboy86]

How does the car run, other then idle?

 

[87blackroxi]

Sorry I haven't responded all weekend I have had family in.
BuBut other than idle, the car runs like a banshee. Strong and fast.
I didn't get to take a look at the car at all this weekend. but I will have to look into the relays.
Thanks fellas.

 

[TriTown]

I had the problem and it was the IAC motor

 

[Vettefan87]

I just got done scanning my car with a scantool. That thing shows everything the computer is doing. If you have access to one of those it might shed some light on the problem.

 

[maxwellgood]

I just ran into the same problem this weekend. Pulled off the air duct, installed one of those intake air foils, removed the top plate and rubber gasket and noticed a lot of gunk in the TB. I didn't have time to clean it out, put it back together and now it idles rough when cold. Do you think it is the same problem?

 

[Doktor-t]

irregular idle

My -88 with automatic also idles a bit incorrectly. Normally the idle is 700 rpms but every now and then it falls down to 600 for a second and then rises to 800 rpms. Today the engine died while being hot (at idle speed) and I put in reverse. It died this way three times.

After this I thought it was time to get down to the problem.

I´ve reset the initial timeing, checked fuelpressure, adjusted the TPS to 0,54 Volts, cleand the distributor cap and rotor, cleaned the throttlebores, checked the ignition-coil but the problem is still there. It haven´t died when shifting into gear since the TPS adjusting. The idle isn´t perfect yet though.

The only thing that I´ve haven´t done is checking and cleaning of the IAC.

Does any got any ideas?


Regards//

Tobias

 

[gmjunkie]

I've had problems with Dirty Throttle body and IAC valves!!!