After the car is warm the idle is around 1200 - 1300 rpm. New items are: Taylor wires, Hypertech coil/rotor kit, NGK plugs, IAC, TPS, and Coolant sensor. Completely dissasembled the throttle body and cleaned it (it was not that dirty). Reset the idle using the paper clip trick etc. Checked for stored codes - none. Checked for vaccum leaks visibly and with an unlit propane torch (2FST4U trick) Disconnected battery cable to reset ECM, still no change. I haven't checked the timing but it has never been touched and ran perfectly for 34,000 miles. Car has 35,000 miles now. Any more ideas? All help greatly appreciated.

Aloha,
Larry

 

When it is idling high can you close the throttle body by hand to reduce the idle? If the throttle body is worn the engine vacuum will cause the plates to open slightly increasing the idle. If you can reduce the idle this way your throttle body is worn. You can add an additional return spring to compensate for this problem.

 

When you installed the new IAC, did you verify that the pintle design was identical to the one you removed? There are at least a couple of different configurations for it and the parts guy could've sold you the wrong one.
Also, did you check the pintle length before installation to insure it was less than 1-1/8" ?

 

Yes, I checked for identical pintle design and length of extension.

No, I cannot reduce the RPM by manually closing the throttle plate.

Any more ideas???

Thanks again everyone.

Aloha,
Larry


[Modified by Larry Mackey, 2:56 PM 11/17/2001]


[Modified by Larry Mackey, 12:37 AM 11/18/2001]

 

Anyone???

 

If min airflow can not be set, look for vacuum leaks. Have you disconnected the power brake booster vacuum line and blocked it off?

Also, the TPS voltage being set too high will raise idle too.


[Modified by BBA, 4:03 PM 11/20/2001]

 

No I have not disconnected the power brake booster vacuum line. What would I gain from this? Could I drive with it blocked.

The TPS is not adjustable on the 91 model.

Thanks,
Larry

 

Blocking the P Brake line would tell you if you have a vac leak in the P B system - but it's a bear to get that line off a '91 plenum.

Did you verify wiring connector at new CTS (near throttle body) is making good contact? Sounds like you are not getting a Coolant Temp signal - wiring can break at that location sometimes.

Did you try blocking off EGR line at exhaust manifold? Stuck EGR is also possible vac leak.

Last thought (wild speculation only) - did you reverse the input wires on the new coil by mistake? If so you might have blown out the distrib module. You might want to pick up a spare.

HTH
drj

 

At this point, I'd recommend following the proceedure for setting the minimum air flow rate. By doing this, your IAC will not be a factor in the diagnostic process. If it continues to idle high (caused by too much air.....NOT to much fuel), then you've got a vacuum leak. If you're able to set min. air flow per proceedure, and it still idles high when the IAC is reconnected, then the IAC or associated wiring is bad.

 

I know the throttle body is super clean. Did it myself when installing new IAC. I went through the procedure of connecting the paper clip to the A-B on the ALDL and setting minimum idle. This only happens AFTER the car is warm. So it seems it must be somewhere in the system that is affected by the operating temperature, such as coolant sensor (which is also new). Thanks for all the ideas. I will keep looking.

Last question - Would any of these things show a code?

Aloha,
Larry


[Modified by Larry Mackey, 2:17 PM 11/20/2001]

 

Not really. If min airflow is too high, Idle will be fine when cold. Normal cold idle has the IAC open quite a bit, then it shuts almost when the engine is hot. Proof of this is when my IAC was sticking, the car wouldn't idle when cold, but when warm it would idle, meaning the car naturally idles faster when hot.

Your IAC motor could be bad or stuck, and especially since you just replaced it, look for something you possibly messed up.

 

BBA,

I had this problem BEFORE installing any of these new parts. The reason I replaced all of these things was in trying to find the high idle problem. Thanks again for all your help.

Aloha,
Larry

 

Sounds most likely to be a vacuum leak with the EGR system. :rolleyes:

 

Man I hope we find out what this problem is. I have the same problem. I have changed every sensor on the engine, checked all vauum lines and changed some, new throttle body, new intake gasket and some other stuff.
Mine actually started acting a little different last night. Now the idle hunts a little. Will idle up to 1200 for a minute or so then drops to about 900, then starts to go back up to 1200, etc.
Larry, If I find the answer I'll make sure to let you know. I'd appreciate the same.

 

Some IAC's have to be reset after install. Depress accelerator slightly. Start the engine and run for 5 seconds. Off for 10 seconds. Then restart and idle should be normal. If not, then you may want to check the wiring and the connector. Ground the diagnostic connector with the paper clip and then with a test light to ground, check each terminal in the IAC connector. Each should flash or show a steady light. If not there's an open in the circuit without the light.


[Modified by SunCr, 8:06 PM 11/21/2001]

 

O2 sensor ok? I see it only has 35k miles so it might be premature unless it was damaged/soiled somehow. Cats not clogged?

 

Here is my question: What idle speed was the FastChip programmed for? If it was programmed for 750 RPM in drive (usually 100 RPM more in park and neutral), then I would generally set my idle to 50 RPM below this.

The main thing is knowing if that idle speed was changed in the chip. If it was, it is pointless to set min. air rate for 450 RPM. Been there, done that. I set it just low enough when the engine is warm to keep the IAC active, but close enough to the programmed value to keep from running into vacuum leaks. -Matt-

 

Do you have access to a scan tool? It would sure help on figuring out this one. I had "the" idle too. I scanned it and found that at times the ecm would command the iac to decrease to 20 counts; but the idle was still high- it turned out I had a bad connection in one wire connector to the iac. Just another $.02

 

89 Paul,New O2 sensor, cats definitely not clogged if you know what I mean :)

High Hpes 85, would Ed W. change the idle speed on a chip for a 6 speed car? Got me thinkng on this one however I am sure he wouldn't change it to 1200,would he??

Drive it, no I do not have a scan tool but it might be my next investment.

Thanks again guys,
Aloha,
Larry

 

You got me on that one, I dunno

Only if he was nuts. :D

OK, the way the IAC works (or is supposed to). It will park to a certain position when you turn the car off. That means when you turn it on, air will be bypassing the throttle plates and will also be bypassing the pintle a certain amount. The idle speed is going to be a result of the 2 vacuum leaks that were just mentioned. Normally, engine vacuum will be around 16-18 in Hg.

When you do the idle reset with the AB discussed above, the IAC will fully extend. When the IAC fully extends, air will only bypass the throttle plates. This setting should only be done with the engine warm, because otherwise, the idle will be wrong.

So when you do that min air set, that is the lowest possible idle your engine can have unless there is an intermittent vacuum leak elsewhere. When you plug the IAC back in, it will use the computer charts to find out how much it should retract.

1200 RPMs means that you might hear a hiss or a woosh from the air intake. That would indicate the IAC is going full open. Vacuum on a gage would also drop to somewhere around 7 in Hg. An overly rich condition on my car caused this, and Boytye8 pointed me in the right direction here. You gotta remember that the O2 is on the drivers side bank, so if any injectors on that side are leaking down or manfunctioning other ways, it will translate to high sensor readings. My car was trying to lean it out, and when it couldn't lean it out anymore, it resorted to raising the idle.

Another thing that could cause a high idle is a request for the A/C when the A/C really isn't on. I'll keep thinking. -Matt-