turbotaloon95

iTrader: (7)

First and foremost, I'd like to make this thread an intelligent discussion and an informative post.

Second, I am in the preliminary stages of figuring out my idle issue. I can still get the car to idle and run fine to get me back and forth to work and wherever else I need to go. I have another project car taking up garage space and need to finish it before the evo goes in the garage for some upgrades and troubleshooting. This means I am just looking to line up diagnostic steps and things to look for before I can provide any feedback.

So here is some back story. The car is a '03 evo 8 that is 99% stock. However it has a walbro 255 and 850cc injectors that I installed a while back. I have tuned it through ecuflash with the latest tephramod rom. With some help from the forum members, I got fuel trims locked down and very close to zero. Otherwise car has a full TBE, K&N air filter and I'm usually running like 25psi on the stock turbo through a MBC and upgraded wastegate. I also recently removed the EGR valve and installed the block off plate. I turned off all egr functions in the ecu.

The car starts up exactly as it should when it is cold. The problem really happens when I try to start the car when it's warm. It starts and catches, but will stumble at like 200-300 rpm, then after a few seconds, it kicks up to 800-900 RPM. An additional, and I believe related, issue is that during idle sometimes the AFR will sweep from super rich to super lean or vice versa. It eventually settles back down to stoic. Drive ability seems to be fine. Sometimes it will stall if I throw it in neutral and come to a stop while turning the wheel or something. Otherwise in boost it feels ok. Sometimes I get knock in the low RPM range when the load is high, but I think that's a tuning issue.

I haven't done a boost leak test, but I've sprayed brake clean around the intake while running to see if there were any obviously leaks. I found nothing. The throttle body was rebuilt like 3 years ago with mil-spec seals and new screws in the throttle plate. T bolt clamps around the intake pipes. BISS was set appropriately with evoscan. Idle is set to 800 rpm.

I have the theory that my FPR is going bad, but I'm not sure how to test that. So again, I wanted to see what you guys thought and what diagnostic steps I can take to help determine the cause of this issue. Thanks!

EDIT: Oh, and I replaced the IAC module earlier this year with a new OEM part.

Biggiesacks

Well it looks like you have a good handle on all the basic stuff. The next thing i would probably look at is your injectors leaking a little after shutdown. What kind of spark plugs are you using? When was the last time you changed them, and what did you gap them to? Are you logging ISCV steps? If so what are they looking like at cold start, cold idle, warm idle, warm start?

turbotaloon95

iTrader: (7)

Yea, I've been doing this long enough to remember the basics! Haha.

How do I check to see if injectors are leaking after shutdown?

According to my records, I put in NGK BPR8ES plugs on July 6 2014, at about 126k miles. I now have about 135k miles. The gap is whatever the FSM said if I recall.

I can most certainly get some logs of ISCV steps and post them up. I don't have any recent logs, so I'll just grab new ones tomorrow and should be able to get all those scenarios.

Thanks!

Biggiesacks

I would deff swap those plugs. The copper ones need to be replaced like every 5k miles. I just do it at every oil change. Do a search for the proper gap for your boost level. I remember OEM recommended gap as being a little over optimistic especially if your on stock coils.

Biggiesacks

As for leaking injectors, i don't really know how to go about checking for that without getting pretty creative. You can easily pull them out and inspect them for gunk though. I would do a search for your make and model and see if others have reported any problems.

turbotaloon95

iTrader: (7)

Ok, I've attached several logs from today from four different parts of the day:

01FirstMorningStart.xlsx

This is my first start in the morning before work. I let it warm up a bit before heading off to work. I included the drive to work. No issues with this start.

02StartImmediatelyAfterFirstShutDown.xlsx

Once I parked at work, I turned the car off. Waiting maybe 5 seconds, then turned it on again and started logging. It started up just fine this time and idled fine.

03SecondStartLunchTime.xlsx

This is maybe 4 hours later as I head out for lunch. Includes start up and drive to lunch. Started fine, idled fine, no issues.

04AfterLunchIncludingStart.xlsx

This is about 30-40 minutes after the last log on my way back to work. I started logging before turning the car over, that's why you see 0 RPM logs. This also includes the drive back to work. This is where the bad idle issue occurs. You can see the idle hovers around 500-600 RPM for a few seconds before it goes up to 800rpm like it should. Target idle is 850.2 the entire time.

To be honest I'm not sure what to look for. Everything looks somewhat ok to me. The things I notice are that the AFR gets pretty rich, like 10:1 right before the motor starts. Not sure if that's an issue. Also the ISCSteps are around 100 on a cold start, the last time it was in the 60's when it started and got up to the 70's once the idle went normal.

What do you guys think? Something else I should log?

Biggiesacks

I think those results kinda lean towards leaking injectors. Other people with leaky injectors have described similar symptoms. Something like a quick restart doesnt give the injectors enough time to slow leak anything, but a start after like 10-20 minutes and enough fuel has leaked that you get a pretty rich starting condition. Which you mention seeing. Left long enough and the leaked fuel evaporates and starting is fine again.

Biggiesacks

Looking at your logs your injector scaling could be a little better. You usually wanna shoot for +-3 on both LTFT Low and Mid. Since its LTFT Low that is most off you wanna try adjusting the voltage latency compensation table.

turbotaloon95

iTrader: (7)

Which direction do I scale the values in the latency compensation table?

And do you think it's worth it to get my injectors sent out for a cleaning and flow test?

Biggiesacks

i would start by lowering the latency one increment at a time. That is, make the minimum adjustment it will allow. flash your ecu then reset your trim via pulling the battery cable. I think it would be a good idea to call the MFG of your injectors and explain whats going on, that you think it could be leaking injectors and see what they say/advise.

turbotaloon95

iTrader: (7)

Thanks for the info! I'll adjust the settings today at lunch and see how it goes. I'll also call up the company. I think they are PTE injectors? I'll have to check though.

The more I think about it, your leaking injector theory sounds pretty valid. That explains why it goes rich when I let off the gas pedal and put it in neutral causing it to almost stall sometimes.

turbotaloon95

iTrader: (7)

I adjusted the latency values down by about ~5% and unplugged the battery. Granted I only did a short drive to work, fuel trim low went from -6.25 yesterday to 3.5 today. Mid went from -3.125 yesterday to 5.664 today.

Below I'm outlining the change in values:

Voltage___Old Value____New Value
4.69______3.480______3.312
7.03______1.920______1.824
9.38______1.680______1.680
11.72_____1.008______0.936
14.06_____0.768______0.720
16.41_____0.600______0.552
18.68_____0.456______0.432

I think I'm going to split the difference on all values and flash it again and see what happens

turbotaloon95

iTrader: (7)

Quick update. My fuel trims look a bit better. LTFT Low is around -3 and Mid is just about 0. I'd say that's pretty good. The idle issue still persists but feels a little better. On warm starts it doesn't stumble AS MUCH, and it finds the 800rpm idle much quicker. So perhaps this has helped the issue, but it has not completely resolved it.

Biggiesacks

Have you replaced your plugs yet? The ones you used are copper and need to be replaced pretty frequently.

THANGEVO

iTrader: (3)

Check for exsaust leaks that could change your a/f too