Idle Problems!!!! Help

[jman123123]

Okay so the story goes my 240 has been through a transmission swap, and much more recently has had a new ka24de dropped in. That being said the idle is very weird. When start from cold it revs up in the 2000's and sits there for a while. Once warm this is where it gets even better. It will sit at 1500 then drop randomly to 500, and have trouble keeping idle only to jump back up to 1500. I have replaced tps, iacv, aac, coolant temp sensor, and am now considering replacing the MAF. Any thoughts or opinions on it. On another note I thought that I had it fixed yesterday because without moving the car just tuning it sitting still the car finally got to sit at 800 rpm, but when I took for a drive I got about a mile down the road hit the clutch and it rested rpm at 3000!?!?!? I also deleted the emissions and I don't think that I have any vacuum leaks that I can find. I haven't taken out the carbon canister yet though.

[pacotaco345]

Are you still using the automatic ecu? If you are moving the idle will stay at 2k rpm for a while and when you stop it'll take a couple seconds before it drops to 7-800 if you do.

[booey13]

Not true...for me anyway. I drove my car with an auto ecu for a year after manual swapping it and noticed no change.

[jman123123]

nah I have a manual ecu in it. I think that I have a vac leak, but I have checked numerous lines and no difference. Now I think that I have a MAF problem or a poor fuel pressure. If I had poor fuel pressure wouldn't I get crappy revs when I give it gas. Whenever I rev anywhere above 1000 it feels great. But anything below 1000 and it seems to be having a heart attack. Thanks for the quick responses too. I have been working on this for about a week now and it's driving me MAD. MAD I SAY!!! I also have not removed my carbon canister yet, but the vac lines are still hooked up to it. Could this be creating a vac leak that would be giving me this problem? @pacotaco I know what you mean there, but it seems that once I have low idle set it randomly loses itself and drops even farther. That's why I have it set at 1500 so that when it drops it dosn't stall out, or ruin my new motor mounts from bouncing around ridiculously. It feels as if it trips over itself for just a couple of seconds then goes back to normal, but it keeps doing it.

[pacotaco345]

Not true...for me anyway. I drove my car with an auto ecu for a year after manual swapping it and noticed no change.

Really? Are you sure its a manual ecu? Cuz I swapped a manual ecu in and it settled the idle down, as soon as the clutch is in it drops to ~750.

[jman123123]

oh yes totally sure. That being said even if it was the ecu then why would I be having this surge. I thought about checking the pcv, but would rather not pull off the intake manifold if I didn't have to

[pacotaco345]

oh yes totally sure. That being said even if it was the ecu then why would I be having this surge. I thought about checking the pcv, but would rather not pull off the intake manifold if I didn't have to

When you shut your car off can you hear a hiss at all for a couple seconds? I have a small vac leak that doesn't really affect idle that I know of because of that. Also, hows your timing? If its too far advanced or retarded it won't want to idle at low rpm.

[jman123123]

no hiss and the timing is spot on. Did that when I dropped new engine in. Food for thought the old engine did almost the same thing when I had it in. The only difference was when I rolled up to a red light if I slowly let the clutch out pull the rpm down to 1000 from 1500 it would stay there, but if I hit the gas it would jump right back up to 1500 and stay there