Rough Idle/Start Up Issues (No vacuum leak)

[CalgaryChris]

A little bit of history. Car is 2005 5EAT stage 2 91 +sf cobb map for almost 3 years now, around 60k miles. (Car has about 95k miles total). Invidia Catless up/down pipe. Not much else done until recently.

 

A month or so ago I noticed vacuum leak symptoms, just rough idle and almost stalling out at red lights and stop signs, exactly like when the stupid blue T has a hose come partially off. I also noticed when I went WOT, boost would be slow kicking in and the car would studder a tiny bit before boost kicked in. I pressure tested for vacuum leaks, found that the stock TMIC had finally kicked it and was leaking out of the common area that everyone seems to have happen. I replaced it with a Process West unit hoping it would fix issues, and not wanting to buy a crappy stock one from the stealership for 550 bucks lol.

 

Anyways, switching intercoolers seemed to fix the idle issue when I fired up with the PW unit installed, and I pressure tested again did not find any leaks. But when I took it out for a cruise, as soon as I went into higher boost (seemed to be at 9 psi every time I realized at that point once I started watched my AP) I would have a slight bog/studder and a very noticeable noise that sounded like wastegate flutter possibly but definitely from the turbo.

 

I immediately went back into my garage, dropped my downpipe, and checked out turbo and wastegate. Everything seemed perfect looking. Wastegate wasn't obstructed, seemed to be closing all the way and would move freely by hand. No shaft play at all that I could tell. As my immediate reaction to the noise coming from turbo when going into high boost was "Uh oh turbo is shot that's my problem" and under inspection it seemed perfectly fine, I bolted downpipe back up and figured I could try and get some datalogs to figure out what was going on.

 

I took the car out for a drive with my friend who is a Volkswagen mechanic and he figured after the bases that I had covered it was probably fueling related. (Forgot to mention that I had a slight misfire issue about 6 months ago, that ended up being a faulty coil pack. Plugs, injectors and coil packs were all replaced, and compression test done). He noticed that fuel pump duty or something was completely messed up, and as that was the only fueling related item I hadnt replaced recently I figured might as well replace it. He helped me replace it with a DW65c (I believe that's correct haha) and we noticed that the O rings from the stock one were completely mangled.

 

With that done, the car would go into full boost no problem, and a bit earlier it seemed with the PW unit than stock even without a tune, and was running the best it had been in a month or two. But after a week or so I started to notice more symptoms of what I thought were from a vacuum leak, and have them get progressively worse. The symptoms being, very high rpm at cold starts and then it would slowly work its way down to normal RPM. As well as the usual crazy fluctuating RPM after driving when hitting a stop sign or red light that I always saw from a vacuum leak. Doesn't really seem to matter if I've been driving for 20 minutes or 30 seconds.

 

So yesterday, I started logging and noticed that my AFR is pretty crazy at start up (I'm pretty sure) but again I thought it could be caused by vacuum leak. I guess I was just very optimistic/hopeful I'd find a half disconnected vac line =( . Again I pressure tested via blocking off the turbo inlet and pressuring up the BOV line. It holds pressure no problem. I cleaned MAF sensor and air filter while I was at it and reset the ECU. Basically no changes at all to the startup/idle of car. Still has the issues that I thought were/have previously been vacuum leak related.

 

So now I am basically running out of ideas and decided its time to turn here for help where I should have weeks ago haha. Main reason I have shied away being that my data-logging knowledge is very limited at best! So my apologies for that. I have read a lot on this forum in the last couple years, but never really needed to apply/practice it, so the last day has been alot of relearning. Hopefully I have gotten some useful info and a start, although I'm sure the some of the parameters in my logs are unnecessary and others are needed and missing, but I am open to any ideas/criticism of what I probably missed haha.

 

Anyways sorry for the novel, hopefully has all the pertinent info. Here's the important stuff.

 

First log is a cold start and second log is idle/slight acceleration after driving for a minute. These are from when I thought I had a vacuum leak so the parameters are for it and probably do not have enough information but the AFR in the first log at cold start seems crazy to me, dipping down to 11.7 and slowly climbing, along with high RPM going down.

 

3rd and 4th are after last pressure test, after I cleaned MAF sensor and reset ECU, hopefully with better parameters. 3rd being a cold start and 4th being idle and acceleration. For some reason I missed DAM in these two. It was at 0.9 the entire time. That was only about half a mile max driving after ECU reset possible reason?

 

Open to any suggestions/feedback/help/you're an idiot figure it out haha. Thanks!

startup.csv

atstopsign.csv

coldstart2.csv

stopsign2.csv

[Dispatch20]

Thanks for the background and all the relevant info! There are a couple things that currently make this tricky to understand:

 

1) You didn't have the DAM recorded on the first two logs. After a fresh ECU reset the DAM is always set to < 1.0. Usually it takes a little time and some boost around 2.5-3.5k RPM to get that to hit 1.0. I'm curious what your DAM was settled at before the ECU reset.

 

2) After an ECU reset, these cars are known to idle very poorly. Stopping at stop signs can cause the car to stall. That happens to everybody. It takes like 20 minutes of driving (or simply idling) before you get a good idle. This makes the last 2 logs less helpful.

 

Comparing our two cars, mine idles at 1500RPM until it gets warm. My car's AFR will actually do a couple of different things on a cold start. If it's really cold outside (<40F), it will drop to 12.9 for ~ 10 seconds which helps warm up the emissions system. Running rich raises the exhaust gas temp for the catalyst. If it's warmer, it seems to drop low for a few seconds and then actually go lean (16-17) for a few seconds before dropping back to a more regular/stoich AFR (14.x). I don't know why it spikes lean for a few seconds in that scenario.

 

You're startup idled at 1900rpm and ran as rich as 11.03/11.14. The stock O2 sensor is actually limited to 11.14, so rich readings are very inaccurate. The stock O2 is just very inaccurate under 12:1 so anything less than 12.0 can't be trusted. In other words, you're AFR could have been 9.1:1 and the front O2 sensor would still read 11.x in the data logs. This is why people install aftermarket wideband O2 sensors (often in an aftermarket downpipe).

 

It doesn't appear as though you have a vacuum leak. That would have probably shown up in the "A/F Learning 1" field as a value > 5.0. That can range from +/-0 up to +/- 15 or 25. A vacuum leak means excess air would be entering post-MAF (i.e. unmetered air), so the AFR would run lean and the ECU would add more fuel to compensate. The result is a high A/F Learning 1 (the idle, low load fuel correction parameter).

 

I do think you have a problem, but I'm not sure what it is yet. So your only problems are related to running rich on startup and the erratic idle at startup and coming to a stop? The 2nd log (at stop sign) was hard to figure out if you were having a high idle or not without a speed reading.

[CalgaryChris]

Yes those are the only problems that I notice, only noticed the richness because I was wondering why my RPM was so high/ all over the place.

 

On those first two logs, and for a few days of driving around previous to the ECU reset I was monitoring my DAM and it was always at 1.0. (Sometimes I would just leave it on DAM not logging for my 30 minute commute and it was always 1.0/1.0)

 

It was only after ECU reset that it was lower (.9). I will go drive around for 20 minutes hit some boost and then get a new log that includes DAM. Were the parameters on my 3rd and 4th logs more useful? Should I change anything besides adding Speed?

 

Thanks for the reply!!!

 

edit: Forgot to mention, not so much just high RPM after stopping, as it will dip down low as soon as I stop (700, then jump up to 1500, then settle to 1100). I do have adjustment idle to +250 or something due to the 5eat stalling with cobb map.

[CalgaryChris]

Well I went for a small cruise in the city, so didn't hit that much high boost or long extended drives.

 

My DAM started at 0.9 again, stayed there for about 5 minutes, then after a red light during one medium footed 8psi or so acceleration to speed limit of 40 it went up to 1.0. As soon as I hit the next red light 30 seconds later back down to 0.9 and stayed there for the rest of my drive. Idle was a little bit better, but still fluctuating rpm and quite a bit of vibration.

 

Anyways this time vehicle speed is included, and the parameter list actually updated and has DAM among others I thought my last two had. Hopefully they are better logs. First one is warm start up after I had driven for about 20 minutes and then gone into store for 5 mins. Second is a short 3rd gear pull (probably very useless). 3rd is at idle after I pulled into driveway. Looks like 0.88 DAM in all logs.

warmstart.csv

small3rdgearpull.csv

idle.csv

[Dispatch20]

Can you clarify what you mean by having 'vibration' and a rough idle? Is your roughness count incrementing on any cylinder? Is the RPM just going up and down at idle, or does it feel like it was misfiring?

 

I'll be curious to see if your DAM does hit 1 and stay at 1 after a few more days. I'm surprised to hear it hit 1 and then quickly pulled back to 0.9. I didn't think it would do that unless it registered a bunch of knock events, so it's unfortunate that wasn't captured on the logs.

 

Here's another thing to think about that may or may not be an issue or symptom. At warm idle, it looks like your AP measured boost/vacuum is about -6.5 psi. Can you confirm that? I believe you should be at around -8.1 psi at idle. If you live in Calgary, its ~3500 feet above sea level. I'm in NY at 350 ft above seal level and my warm idle vacuum is -10.3 psi. Be careful if you research this topic as psi is roughly half of the typical "in hg" measurement unit. Use a site like this to convert. And more info here on engine vacuum. A reduced vacuum at idle might just be indicative of the throttle not being as closed as it could/should be.

 

Is there an issue with the throttle position sensor (TPS) or a dirty/sticky throttle body that is affecting your idle? The throttle pos % never goes below 9% and sometimes is at 12% during idle, which seems high to me. My car idles at 4% throttle position when warm. If the throttle body needed cleaning and couldn't quit close properly, then more air/fuel would be burned at idle which would raise the RPM. Or if the TPS was a little noisy/dirty it might confuse the ECU and cause the unstable and cycling idle.

 

I've also seen front O2 sensor problems manifest themselves in strange ways.

 

I am just tossing out ideas here. I am far from an expert on any of this. I'm at my limits of debugging this issue, so hopefully someone smarter can chime in!

[CalgaryChris]

To clarify, my idle seems to be fluctuating up and down at idle, the vibration being...I can feel the car shaking slightly in the steering wheel...can't say for sure if it feels like a misfire as the only misfire issues I've experienced were at WOT. Have not noticed any roughness count but I have been more focused on other parameters, so have not checked too much.

 

I noticed the TPS was never lower than 9% as well but couldn't find any reference for what it should be at idle. I was suspecting that this could be an issue. I guess inspecting/cleaning throttle body will be at the top of my to do list for tomorrow. I also grabbed a new 02 sensor today to pop in and see if there is any difference.

 

I also did notice that boost (or vacuum) at idle is off, but I was attributing that to the higher RPM. If I remember correctly normal vacuum was about -8.2 or so not -6.5 im seeing.

 

Will grab some roughness logs tomorrow as well as clean TB and TPS and throw in new front O2 sensor. Hopefully that puts an end to it.

 

Thanks for taking the time to help me out Dispatch!!

[Kemptemp4]

Op ever figure this out? Having misfires on all 4 at lower rpms especially

 

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[xt2005bonbon]

Op ever figure this out? Having misfires on all 4 at lower rpms especially

 

Sent from my SAMSUNG-SGH-I337 using Tapatalk

 

probably a vacuum leak. check the blue T underneath your intercooler and see if some hoses popped off. Very common.

[Tuning Alliance]

Do a low pressure boost leak test, whats your vac at idle? Also you logs look like not 0% throttle (idle).

 

-Brian