High Idle Issue...
 

Some of you guys my have been aware about this issue I've been having. The idle surging idle is mostly fixed after replacing the poor quality "leaky" oil catch cans with ones that are properly sealed (Morimoto) along with proper fuel line hoses for the PCV. I also tightened the PCVs on the valve cover, trimmed and tightened hoses. There's no oil vapor residue anywhere.

Upon warming up idle is so much lower and virtually stable, so it wasn't surging like it did before. However, after driving for awhile (as things heat up), it starts surging slightly (nowhere near as bad as before). Then after 15 minutes of driving and stopping at the light, idle starts hanging around 1-1.2k. If I tap the throttle, the engine revs to 3-4k RPM then slowly back down and back up to 1-1.2k. Up until yesterday it would hang long enough to throw a high idle code. When it does idle high, in 1st the car would accelerate as if the throttle is stuck and I had to hit the brakes to slow it down. At this point the cooling fans are running, and there's lots of heat. No overheating issues.

The work around is to shut off and restart, and goes back to idling low and fairly stable. Some suggested it might be a tuning issue after doing all the maintenance work last year (spark plugs, clean throttles, etc.).

Other than that, engine is smooth, boost is stable, and there's plenty of power.

I have had the exact same thing for a while now and it drive me crazy at times. Planning in the coming weeks to do some upgrades with fuel pump, injectors and new GTR spark plugs plus changing from Uprev to ECUtek for a custom tune. I have been thinking the same in terms possibly the car needing a new tune to solve the problem. It might take me about 3 weeks but i should let you know if the tune was the problem.

Ditto... still on stock canned tune from GTM. It's a daily driver, so nothing too extreme. I'd definitely make the switch to ECUtek as well, but I've got other priorities. :(

Part of that new tune needed acceleration is a bit sluggish or slightly hesitant under 3k when I fully depress the accelerator pedal, but that's been an ongoing thing. I think it's too rich.

When i scan it for codes it hit me a p0300 which is random misfires. Even air/fuel ratio been out of whack can cause the stupid p0300 code. I have check for vaccum leaks, oil leaks and clean the maf sensors and no luck. As part of the code it did mention ignition system,fuel system or a/f ratios been mess up. Thats why now i am going to do some changes to the ignition system and fuel system and then go for the tune and see what happens.

what injectors are you running? I had the same issue for a while, and it progressively got worst and worst. Before i would clear the code, and it wouldnt come back for a while, then it started happening every time i started the car even after clearing the code. It was doing it when i had uprev and when i had ecutek. Problem went away when i switched injectors to id1300

Injectors have cross my mind as well for this idle surging thats why i am gonna try different ones. I am running Bosch 650cc injectors but going with ID 1000cc. Thanks for the info.

That is a great choice on injectors. U might make a bit more power just by switching those injectors too. I gained like 50whp and 70lbs just from swapping injectors. Anyways good luck w that issue


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Thanks man! :tiphat:

Whats your AFR at idle, when the idle goes up and down whats your AFR doing?

I looked at ID750 to replace the Bosch as part of the retune... what a long list of things to do.

I'll get some datalogs from Osiris this week. I drove to work today in much cooler weather. It didn't hang at 1k, but slightly surged between 800-900 RPM by the time I got to work.

Ive seen this with a vacuum leak, Your ecu might be reading to much air. Its causing the Ecu to dump more fuel, in turn raising your idle and making it unstable.

The AFR will tell us a lot.

You're correct! Unfortunately it can be vacuum leaks as well as a few other things thats why in my opinion the p0300 code is the most annoying one. I'll be taking the car to the shop hopefully by next week if i get the injectors in time to go thru all the possible problems it could be and let the OP know.

Yea it could be... with the old component reinstalled the engine bogged when I sprayed underneath the intake plenum. So I replaced the intake plenum, bolts, and gaskets, and it didn't fix it. I even had a mechanic friend check and tightened the bolts. Taking everything apart just to remove the intake plenum is a pain. I've done it several times, and I don't have the time and patience to do it anymore.

This is after a 25 minute drive home, and I left the car idling for several minutes. It started surging again, and it's the first time doing this again. Before it would hang at 1k until it throws a code, but it's not even throwing a code.
https://drive.google.com/open?id=0B1...mxhd1lJQ2FJNkU

This is after a few minutes of cooling off and restarting. Idle surge isn't as bad. If I let it cool down longer, idle will be more stable and lower.
https://drive.google.com/open?id=0B1...WtGSnBrWHg4NVU

Here's the video:
https://drive.google.com/open?id=0B1...2E2MUFCc0tjNFk

It seems like idle surge is pretty bad when things heat up to the point the cooling fans kick in. If I let it cool down it starts idling just fine without the crazy surge. I also sprayed underneath the intake plenum, and it did not have any effect. Before the engine would hesitate. Idle tends to climb up to 1k and dropping a few seconds after starting the car. It has been doing this since I finished the maintenance work last year.

The one thing I've not done since changing out the oil catch cans is to reset the ECU (fuel trim) and whatnot. While idling in the garage it smells like raw fuel. Things seem to have improved over a week ago after installing the new catch cans, but now it's getting worse again.

I've been wondering if my MAP sensor has gone bad. Is there a way to test it?