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?

I think any OBD11 scanner with data logging capabilities can watch the MAF voltage.

We need AFR's my friend, get me a video of your AFR while the car is doing this.

Make a 10$ smoke tester, smoke test it.

Once you know you have no Vacuum leaks, move onto the next thing.

Next thing is to check and make sure you BOV are working properly,line has come off, fully closing Etc..

Im assuming you've checked for cracked manifolds? (smoke test will show this)

Could be a waste gate problem too. Again smoke test will tell us.

If you build the smoke tester I will come :)

build one, sykpe me or facetime me, Ill run you through it, and try to Diagnosis it for you.

Thanks for offering to help. I got rid of Skype earlier this week. I hardly use it, and somehow my account got hijacked, and some stranger wanted to talk/spam me.

I'm using UpRev Cipher to log the data. I'm sure I can make a smoke testor using a jar, some hoses, and a small pump. Do I pull the intake filters and plug one end as I feed it? I haven't checked the exhaust manifolds since I didn't have the tools or patience to remove the heat shields. The BOV was shipped to TurboSmart for service and cleaning, and it's working just fine. The lines were fully secure as tight as possible with the zip ties. It's difficult to twist the hose. For the wastegate, I'm sure I'd notice some funky spikes under boost. It's pretty steady.

I've been hearing some "hissing" noise from the PCV with one being louder than the other, so I further tightened the hose and the noise diminished. Maybe that might help a bit.

Here's the log of the engine warming up before performing the idle relearn:
https://drive.google.com/open?id=0B1...jdyNTIzdW5IQkE

This is during the relearn, and I revved it a couple of times before shutting down:
https://drive.google.com/open?id=0B1...jdyNTIzdW5IQkE

Engine restart and let it idle for awhile to observe idle RPM:
https://drive.google.com/open?id=0B1...jdyNTIzdW5IQkE

Shut off, restart, and let it idle even longer to further warm things up:
https://drive.google.com/open?id=0B1...jdyNTIzdW5IQkE

Here's a plot of engine RPM, AFR bank 1 and 2, and coolant temp of the last log. I wanted to see how warm it usually gets before it starts acting up again. I didn't have time to drive around or run the engine, so the fans never kicked in. The next plot is just a a composite image.
https://drive.google.com/open?id=0B1...jdyNTIzdW5IQkE
https://drive.google.com/open?id=0B1...Gh2UHVHcUxaM0U

So far it appears AFR hovers around 14.5-14.8 peaking around 15 while idling. I can't tell much of a difference when it is fairly stable as it warms up and when it starts to surge between 750-900 RPM. From the plots, when the coolant temps hit 86F is when idle surge becomes slightly more noticeable. I haven't driven the car to get engine "hot" to see if it acts up again. Also, from the plots, you can see the engine slightly revving up close to 1k RPM then back to idle after starting it up. It happens as it warms up or or after a warm start.

I think I can relate to this thread:
http://www.the370z.com/tuning/93796-...induction.html

See in 1st post with video Cell posted "Bouncing idle," and that's what I'm seeing.

Just got home from driving around, and it wasn't surging as bad until I briefly floored it in 1st and 2nd. I could've sworn the fans weren't running, but I felt a hot breeze on the driver side. No CEL, but ECU logged P0507 again. The video below explains what happened tonight.
https://drive.google.com/open?id=0B1...WhpbWp2cU9pNE0

Log after coming home:
https://drive.google.com/open?id=0B1...kVMX21ETmI3bUU

After shutting it down and restarting, it doesn't hang at 1k RPM anymore:
https://drive.google.com/open?id=0B1...kVMX21ETmI3bUU

I don't know... AFR doesn't look too much different, but it's in the high 14s and peaking around 15.

FF to 40 seconds. It was fixed with a custom tune. No one could ever explain why it happened on the canned GTM tune.

I'll keep digging until I find time to drop the bumper and do some leak tests. So far I can drive around town (including freeways) without it freaking out if I don't drive it hard. I've had the oil temps hit 190F, so that's quite a bit of driving. It's still hunting, but between 750-850. MAP sensor isn't too expensive to replace, but I'm going to do some more reading. The next time the car gets lifted I'll try to check the intake manifolds as well.

The reason why I suspect the MAP sensor is because I soaked it in soapy water. I didn't think it would harm it since it looked sealed.

I'll be taking the car to the shop tomorrow to install new spark plugs, 1000cc injectors, fuel pump and a new custom ECUtek tune. I'll let you know if they fix the problem and what was it exactly. :tiphat:

On a relatively cool (under 50F) drive to work this morning I could not get the engine to freak out after stomping the pedal a few times (peak boost 9 PSI, RPM around 4-5k). It hunted a little around 750-850 RPM as usual, but none of the high idle weirdness after brief hard driving. No codes either.

It'll hit 60F for the high today, and I'll see how it goes from there. I'm getting some logs for a friend, but I don't have the parameters he's looking for (engine load, fuel trim, etc.).

Did you ever find out what was causing your weird idle?

Well this was a nice, informative and highly detailed thread until OP abandoned it…

Did you ever pin this down?

His plastic waffle intake was leaking. Can't remember if he replaced it or new seals. I think he replaced it.

His intake plenum? Interesting! Thanks