Under little throttle (1-5% is my guess) it acts like it has an IACV idling issue. But, it only happens after the car has been warmed up, shut off, then started again.

I've never seen this happen before, any help will be great.

 

d16z6, forgot to add that.

 

Missing critical information - What car do you have? Any mods?

When was the last full ignition system tune up?

 

I apologize. I have a 1993 Del Sol with intake/ Exhaust. No check engine light. I haven't gave it a tune up since I've had it. But it doesn't seem like a "tune up issue" And I believe it was done a couple months before I got it. So less than a year. when I rev it up to about 2k it will jump up to about 3500 then down to about 1500. Exactly what a bad IACV would do, but only under a little bit of throttle, and only after it's warm and has been shut off and started back up before fully cooling down.

 

Does the light work?

Time for a tune up. Then go from there.

What brings you to this conclusion?

Sounds like you're guessing and don't really know.

The IACV only affects the idle speed without the throttle pedal pressed down.

 

I got the car from a friend who drove it to and from work. I just talked to him, and he said he did tune it up before I got it from him. I've had issues with cars needing a tune up before, which is why I believe it's not an issue like that. Yes the CEL works, 100% positive on that. Yes, I understand about the IACV and it affects the idle. I'm just using that as an example of what it does when revved up just a little bit. It has the same up and down revving pattern as a bad IACV would have, just not at an idle.

 

How did your friend define "tune up"? Can he verify with receipts? What brand parts did he use? Have you carefully inspected the plugs, wires, cap, and rotor? Is the ignition timing set to spec?

 

I'm not sure about the timing.

I've very close friends with him, I don't need receipts to believe him. I'm not 100% sure on what brand of parts he used, probably auto zone stuff. He did plugs, wires, rotor, cap, and fuel filter.

 

Sometimes friends and business are not a good mix.

Do yourself a favor and inspect the plugs, wires, cap, and rotor carefully. The spark plugs should be the NGK ones recommended in the service manual and gapped to spec. Aftermarket plug wires from auto parts stores are notoriously bad. Ask me how I know.
Inspect the cap and rotor contact points. Check for oil and dust inside the distributor.

Check the ignition timing.

Always start with the basics and then go from there.

 

I just found it to be a very odd problem. I'll check that tomorrow.

Let's say, for example, everything checks out. Any suggestions?

 

Maybe air in the coolant or a small vacumm leak

 

correct me if I'm wrong, but wouldn't air in the coolant, or even a vacuum leak do it all the time? not just after a shut off and back on.

 

I had the same problem and it was a vacumm leak.

 

Q