Thread: High idle in timing mode.

Ok, so I have been chasing issues on my 93 G20 for months and I am about out of ideas.

Here are the symptoms:

-Idle jumps up to anywhere between 1300-2000rpm when the TPS is unplugged (making base idle and timing adjustments impossible)
-My gas mileage sucks (16-18mpg) mixed city/highway
-Idle wanders at times and feels slightly rocky.
-Hesitation around 2000-2600rpm when accelerating under light load.

Now in my experience with ser's and g20's, I know when the base idle and timing are off, the car can perform quite bad. So, I'm thinking that most my issues might stem from that. I have set my timing and idle as best I can, but as mentioned above, I can't get the idle to drop in timing mode. I can get it into timing mode, but no matter what I try the revs stay high.

Anyways, I have picked over about every sensor you can think of, checking them with both a multimeter and via consult on my laptop. Everything has been within FSM specs. I have tried swapping many sensors with known good parts with no luck.

The only odd thing I have found is with the AAC valve. If I disconnect the TPS and start the engine, the idle jumps up and the AAC valve will go to about 75% and freeze. Even if I rev the engine it stays locked at 75%.
If I plug the TPS back in the idle drops to normal and the ACC valve drops in the normal range.

So my question is:

What would be the connection here? Why would the AAC valve jump up and freeze only when the TPS is unplugged?

I have tried swapping the whole IACV with an extra one I had laying around (both were cleaned well) but it changed nothing. Perhaps, I have two bad AAC valves? Bad wiring?

Any input is appreciated.

when i didnt have my air regulator i would have the same problem after i got the regulator i could set my timing

Hmm. I have tested the air regulator and it is to spec and I took it off to physically check it. I took it off the car while the engine was still warm and when removed the valve was shut like it's suppose to be. I let it sit out by itself and cool off for about a half hour and the valve had not opened. So I stuck it in the freezer for a few minutes to see if it would open and it did. I also checked the resistance and it was fine. I'm assuming the regulator is ok.

Are you using a cold air/ warm air intake? Did you do the Maf grounding mod?

I've heard stories about some SR20s that need the IACV to be unplugged before base idle can be set. Not sure why this happens, but it does. You might give it a try.

I have a jwt pop charger and yes I have re-grounded the MAF...it needed that pretty bad. However, the reground did not help the problem in question.



Very interesting. I have never heard of this. I'm assuming I only need to unplug the AAC valve on the IACV, or do I need to disconnect the both connections on the IACV.


Thanks for the feedback by the way.

Not sure -- see if either or both works.