strange idle issue when warm

[The Bimm]

Okay so, I have a 88 m20 b25 swapped into a 87325e. when my engine is warming up, and the temp gauge tach goes right above the blue line, the idle will be rougher. It almost feels like it's misfiring, and then while driving I take my foot off the gas, and push the clutch in to throw it in neutral the rpms will drop to about 500 then jump back up to 900, or 1000 where the engine idles at. It happens almost every time.

[jlevie]

That sounds like it could be intake leaks, which would be the first thing to check. Have a smoke test run.

[The Bimm]

I did, and the only vacuum leaks found was on the fire wall side of the valve cover, and a tiny one coming from the top of the tb. But that was a while ago, I should probably do another one. For some reason I have a feeling it might be the intake manifold. Would a afm be the cause of this?

[Quinthirty]

When was the last time yu changed the o2 sensor?

[The Bimm]

About 4 months ago when I had to get some new parts for smog. It passed with flying colors, but I do know that the smog guy adjusted the afm, and it started to act up a little after that.

[Poorboyz]

Did you use the "E" AFM or the "I" when you did the engine swap?

Sent from my Galaxy Nexus using Tapatalk

[The Bimm]

I used the I afm. I got it from a friends running m20b25 because he was in the middle of a m50 swap. I did just find another afm in my old parts box that I got from the junk yard. Ill give that afm a try and see what happens. I also had to cut, splice, and extend the o2 sensor wires to make it reach down to the e exhaust o2 port. Ill check and make sure those wires didn't get messed up over time.

[mathillois]

cover all the basics first. start with a smoke test to find any leaks and fix that, if thats not the issue then i would move to ignition wires and plugs and distributor cap and rotor.

[The Bimm]

Yeah, I'm going to do a smoke test tonight. Then I will change my plugs. cap, rotor, and distributor are new. I will update when fixed.

[essi1553]

I had a similar problem, turned out to be a bad Idle air control valve. Its an easy test to see if thats the problem.

Start the car, and disconnect the plug for your ICV, if the idle doesn't increase, you have a bad ICV. You can try cleaning it, sometimes it works, I needed to replace mine.

If you don't have an air leak, or some kind of ignition problem, i'd test that next.

[The Bimm]

I ran a smoke test, and only found 2 small vacuum leaks. Those were a easy fix, but It didn't fix myprproblem. I did unplug the icv while the engine was running, and it didn't change anything, so I think that is my problem, but I can here it buzzing with the ignition on, and from what I read that means it is working right? Next I will do a scope test to see if the o2 is working properly.

[essi1553]

Change your ICV, id try spraying a shot of wd-40 in there, maybe it's stuck. But if you'd idle doesn't change it's bad, its a simple fix. I'm like 95% sure it's the issue, if it didnt pass the test.

[essi1553]

Any updates here?