Just another misfire/rough idle thread...

[StkmltS]

I'll bet 6 Internet points that it's a vacuum leak, either the IM orings or the throttle body hose.

 

Sent from inner space.

[fahr_side]

Just had a thought - this always seems to start around October, end around February (IIRC). Winter gas??? I'm in CA, and our 91 is already notoriously bad..

 

 

 

Remember total timing is also compensated for IAT

[hadvw]

my guess is, if you don't have a vacuum leak, then you may be having a few exhaust valves getting tight. It may be time to check the valve clearance. How many miles on this engine?

 

125k miles. 60k+ at stage 2/3.

[hadvw]

I'll bet 6 Internet points that it's a vacuum leak, either the IM orings or the throttle body hose.

 

Sent from inner space.

 

I recently checked the throttle body hose again - ever since I installed the Grimmspeed TMIC, those hoses have been popping off regularly until I REALLY tightened them down.

 

O-rings are a definite possibility, though..

[xt2005bonbon]

So let me restate your issue cause I've been following other forum members with similar misfire problems and I can get mixed up

 

When your engine is cold and idle, it does not miss.

When the engine is at operating temp, it idles rough. And when you push it a bit, it stumbles.

 

Am I correct?

[hadvw]

Note quite. Let's define 3 operating conditions: cold, warm, hot.

 

cold is cold start, temp gauge pegged at the bottom (let's call it 6:00 o'clock, even though it's really not)

warm - coolant has warmed up enough for idle to start to drop, temp gauge at the first "warm" marker, or a little past.

hot - coolant gauge firmly at 9:00 o'clock.

 

cold is fine

hot is fine

 

that 60 to 120 second cold-to-warm transistion has hesistation, misfires, stumbles and occasionally stalls (when idling) in traffic. Btssm shows knock events, cylinder misfires, etc. But only when ambient temp is below approx 65F (which is October-Feb or March here in NorCal). During the summer, this does NOT happen - at least not as noticeably, and no stalling. So the colder ambient temps make it worse somehow.

 

Now, it looks like I might have the occasional knock event as well when hot, thanks to btssm logging. But, as bad as it sounds, I don't really care about it that much. Not stalling/stumbling in rush-hour traffic is my #1 concern.

 

I just got an updated tune from my tuner, haven't had a chance to try it yet. Will flash that tonight, and log some more..

 

Thanks for helping.

[heiche]

If your updated tune doesn't help, it almost sounds like your AFR sensor is going bad. It could also be other things, but that would be my first guess.

[hadvw]

I replaced the AFR with a new Denso OEM sensor about 2 years ago - would be maybe 10-12k miles ago.. (replaced both sensors, actually). I DID move/disturb the rear sensor when going from gutted OEM pipe to CNT catted pipe this summer, but it sounds like you're talking about the front sensor.

 

Could certainly be going bad. Maybe I should check to see if I still have the old one lying around. I doubt it. But car seemed to run fine for quite some time after changing, so it wasn't bad to start with, AFAICT.

[heiche]

Yes, I was talking about the front sensor, but since that one is recent it's probably fine.

 

Did this problem start happening around the time you had to remove/reinstall the rear O2 sensor?

[hadvw]

No, moved rear O2 in the summer (June?). This just started about 2 weeks ago - just like clockwork. When the temp drops outside, this starts.

 

It was much worse when I first got pro-tuned with my APv1 (bnr16g, DW650cc, walbro, gutted OEM pipes) 5-6 years ago - that was when it started. Did not do this stock, or with OTS stage 1 (Cobb) or OTS stage2 (TDC, VF40 + gutted OEM pipes) tunes.

 

It would stall regularly once or twice a day on the same route until I used freessm to up the idle (which I had to do every time I reset the ECU, got annoying). Also threw CELs. Upping the idle targets got rid of the stalling. I added a grounding kit at that time, which made no difference. But again, only with colder temps outside. >~70F outside, everything's fine.

 

Since then, I got e-tuned with opensource. For 3-4 years, this was better - still there a little, but not as bad as this. Which was one of the main reasons to try e-tuning. It is worse this fall than last year, to the point it stalled once. I also saw a misfire in cyl3 again today, and one in cyl4. That's why I'm trying to figure it out again.

 

Various changes since this started with the APv1: IP&T oiling kit (shouldn't make a difference), replaced O2 sensors (both), have changed plugs a couple of times, went back from non-OEM filter (not K&N, the other non-oiled kind) to OEM paper air filter. Cleaned MAF. Tried to clean throttle body as best as I could without removing it. Could it be a dirty air filter? I cleaned it out recently, but it's still 2-3 years old, probably.

 

One thing I did this summer, along with putting in the Grimmspeed TMIC and the CNT catted DP was to replace the OCV valves, trying to see if that would help.

 

As far as I can remember, I'm still on original coilpacks.

 

When this happens, if I have enough time at the red light, if I drop to neutral and rev a few times up to 3-4000, that seems to be enough to get over it. Not good for the car, I know, but, oh well.

 

Of course, that's the problem - it's hard to reproduce, because it ONLY shows up for 1-2 minutes when warming up. Take it to a shop, and they have to do it overnight, and ideally, drive the same route to see anything. Warm, it seems to run just fine. Well, at least in the past it was. This year, it seems to hesitate just a bit when hitting WOT, but that may just be my imagination..

 

Sorry for the tele-novella...

Edited October 12, 2016 by hadvw

[heiche]

ah, ok, if it started around the time of your tune 5-6 years ago, it may indeed be tune-related. Sorry to OP, didn't mean to derail thread.

[StkmltS]

Derailments like this are very welcome. Every time we venture off on someone else's car I learn more about mine and it gives me new areas to research.

[DuCKy1657616051]

Hi OP

 

Looks like you're still battling here. Props to you for being so persistent!

I've been told to come here to check a few things? Maybe you can also help?

 

Sorry for hijacking, if you don't mind?

 

Blue line is my RPM

Maroon line is my injector DC %

 

http://i.imgur.com/XoGwZMJ.jpg

 

My RPMs fluctuate +/- 70rpm irregardless of cold,warm,idle, load.

I get that misfire/surging affect.

Looks like my Injector DC% directly correlates with it? The fluctuation is 0.1% whenever the RPM fluctuates.

 

I've also been getting misfiring #3 on BtSsm recently. Would climb up to 15 counts when warm idling.

 

What would you suggest trying first?

 

Cheers!

Nicholas

[xt2005bonbon]

I've also been getting misfiring #3 on BtSsm recently. Would climb up to 15 counts when warm idling.

 

Have you tried swapping coil packs between #3 and #1? Same question with spark plug and injector? If you've already tried all three and the count still stays in 3, then you may want to check your valve clearance next. My 05 was doing something very similar in #2. I tried everything. Turned out one exhaust valve did not have any clearance. Luckily, I did not wait too long to check, or else it would have resulted in a burnt valve.

[heiche]

FYI "Injector DC%" is derived from RPM (and injector pulsewidth). My point is that if RPM fluctuates, Injector DC% will mathematically fluctuate as well.

 

I would probably focus on the RPM fluctuation and not get too hung up on the Injector DC% fluctuation.

 

Like with StkmltS, I wonder sometimes if the crank sprocket or the crankshaft position sensor might be contributing to this? Certainly bonbon's suggestion is a much easier/economical first thing to try.

[birkhoff]

The noisy plot on that RPM curve kind of stands out, doesn't it.

 

Out of curiosity, I fired up one of my logs and snipped out a chunk of the rpm curve. I chose a time interval where everything was stable, no misfires etc. Just a completely boring chunk of log. When I plotted the RPM vs time I got the following graph:

 

http://legacygt.com/forums/attachment.php?attachmentid=239262&d=1476548761

 

 

Keep in mind that the time units are milliseconds. What I find hard to believe is the oscillations on the order of 30 - 50 RPM multiple times per second.

 

My car has had rough running issues and misfires, but it is stable right now. My question is, how is the crank position, timing, misfire detection etc supposed to work with this kind of noisy signal?

 

The engine has a brand new crank gear, but used (180 K) position sensor. I have not done any tests on the sensor.

 

With all the discussions on this forum about rough running, timing issues, misfires and whatnot, I cannot seem to find anyone who has replaced their CPS in an attempt to solve their problem. Given that so many calculations at the ECU depend on this signal, I'm kind of surprised.

[heiche]

Just to add a little more info to the jagged RPM plots, I've seen posts for other SSM software readers experiencing the same issue. Not sure why the ECU would output these small fluctuations in RPM over SSM. But it does seem typical.

 

However, what is NOT typical is ducky's RPM plot with the occasional sharp peak or valley.

[StkmltS]

I'd like see this thread keep going in the direction it's been going (other people's misfire issues) but real quick... how much of a difference should I see between my stock front O2 and my new wbo2? I haven't driven with it yet, but I installed it this morning and at first glance my wbo2 seems to be reading about 0.2 higher AFR at idle than my stock O2 sensor.

 

Sent from inner space.

[fahr_side]

Quite normal. The more sensitive a sensor is, the more tolerance there is on the measurement. I use the front O2 for all tuning operations in CL and the WBO2 exclusively in OL.

[DuCKy1657616051]

Thanks StkmltS, will try my best not to spam here

 

I haven't spent any time under the bonnet yet actually, my weekends have been pretty full on! Also, thanks Heiche for clearing that up. I don't need to scratch my head over my Injector DC % relative to RPM anymore.

 

 

Thanks to others, I've been adding more fields to log.

It seems that my VVT Ex L&R don't play too well together!

They timing is so far out at times. The duty cycle also do not really follow each other well.

 

http://i.imgur.com/wNbpdUf.jpg

 

 

My Exhaust OCV valves need cleaning/replacing?

[heiche]

Good catch on OCV issue. The Left Exhaust VVT is definitely "lazy" compared to the Right Exhaust. Maybe a new OCV would clear that up? I had a similar issue, removed and cleaned it, which made it a little better, but eventually replacing it got it back to where it should be.

 

Note that it's not always the OCV. Low oil pressure getting to it can contribute, if you have a banjo bolt filter there it may need cleaning/removal. But it seems like it's often just the OCV itself that's the issue.

[xt2005bonbon]

Good catch on OCV issue. The Left Exhaust VVT is definitely "lazy" compared to the Right Exhaust. Maybe a new OCV would clear that up? I had a similar issue, removed and cleaned it, which made it a little better, but eventually replacing it got it back to where it should be.

 

^Yeah, they should be in sync at all times especially under load.

 

Note that it's not always the OCV. Low oil pressure getting to it can contribute, if you have a banjo bolt filter there it may need cleaning/removal. But it seems like it's often just the OCV itself that's the issue.

 

^That is also true. So do check your banjo bolt filters if they're getting clogged. It could kill your turbo too..

[StkmltS]

Quite normal. The more sensitive a sensor is, the more tolerance there is on the measurement. I use the front O2 for all tuning operations in CL and the WBO2 exclusively in OL.

 

Are you saying the stock O2 sensor is more sensitive, or the wbo2 is?

 

Here's what it looks like at idle. Both charts show the same data, I just changed the axis min/max in the second chart to better show the difference between stock (front) AFR and wbo2.

BtSsm_20161018_061509.csv

[StkmltS]

ALSO

When I'm at 0mph and missing like a maniac, if I repeatedly tap the throttle the misses stop increasing. I have no idea what to think about this.

BtSsm_20161017_060205_chart.csv

[xt2005bonbon]

ALSO

When I'm at 0mph and missing like a maniac, if I repeatedly tap the throttle the misses stop increasing. I have no idea what to think about this.

 

Check the usual suspects once again