Weird cruising misfire, DAM = 0.2, but no FKC/FKL

[lagwagon]

Just trying to get my thoughts and memories down quickly before I can post a log to see what might be the problem here:

 

Cruising at 100km/hr, slight uphill, 30 minutes into the drive, car starts misfiring slightly (no audible knock). Car starts smelling like gas (no other cars on the road). 10:30 pm, 0°C outside. Pull out the AP and plug it in and DAM is down to 0.2, start watching FKC and FKL (AP v2 so no multi gauge view) and don't see anything happening there. Misfiring is gone by the time I get the AP out. Gas smell goes away a few minutes later.

 

This morning, DAM goes up to 0.4 in my 10 minute drive to work, still no FKC, FKL registers +0.9 (adding timing) under 2000 rpm a couple of times which isn't unusual. I have 1° pulled globally in the AP but otherwise OTS stage 1.

 

Trying to figure out if DAM only reacts to preignition or if it will react to other misfire events. This felt like a lean miss or spark blowout, either of which could result in the gas smell if the computer dumped a ton of fuel to correct the lean condition, or I was smelling unburnt fuel from blowout.

 

Car had an oil change less than 500-km ago and they usually pull the plugs to check them and they didn't say anything unusual was going on. Also had a coolant system pressure test and exhaust gas test done since I had some major misfiring/knock events (again nothing audible, but similar cruising conditions other than it was +37°C, not 0) on what I believe was a bad tank of gas in the summer. Everything came back fine on those tests.

 

I'll post a log I took on the drive last night but I didn't see or feel anything unusual when it was logging.

[xt2005bonbon]

How are you fuel trims? I always check these. Also, log misfire per cylinder.

[lagwagon]

How are you fuel trims? I always check these. Also, log misfire per cylinder.

 

A and B are between -4 and -5, C and D are between -1 and 1, but really close to 0 (like -0.3 I think).

 

Do you mean cylinder roughness? I've had a hard time logging multiple additional parameters, it usually crashes and doesn't log, probably because it's a V2.

[xt2005bonbon]

-4 and -5% is not too bad, but it is on the negative side still. Just double check if you have any vacuum leaks.

 

Yes, cylinder roughness.

[MoleMan]

Just throwing this in.

 

Winter blend is upon us. Maybe run a bottle of Techron and fill up with ethanol free and see what it does before chasing issues. It can’t hurt.

 

Yesterday My daily was hesitant to start in 7 degrees F and did smell like fuel for the first few highway miles. My bet is still on a bad tank of gas. Tends to run like crap for a month after they switch from summer to winter blend and then back in the summer.

 

Once again try filling up and use a fuel cleaner like Techron concentrate. If you have the same issue or are having the same issue by mid tank then start chasing down the gremlin..

[lagwagon]

Here is a datalog with cylinder roughness. The first log I took had no useful parameters being monitored. I'll need to turn on some more knock parameters and see if it will log with them selected.

 

I only see counts of 1 in cyl 3 and 4, including a short wot run in 2nd gear, up a steep hill (near the end of the log). Everything looks ok but all the roughness seems to be at steady cruising.

 

I'll try to take another log today. Current issue is my old laptop with USB 1.0 is incredibly slow and this took me over an hour just to save the log and transfer it to a USB stick to use on my main computer.

 

For the Techron, not sure what that is or if it's available in Canada, never heard of it or seen it. Also, I don't think I can get non-E10 premium anymore. There is some local debate currently if Shell v-power is still E0 as they have removed the "ethanol-free" stickers and replaced them with "may contain up to 10% ethanol" stickers at some stations. Some tests have still shown no ethanol. The bad tank I had in the summer was Shell v-power 91, and honestly, the car ran like it was 87 so I haven't been back to that station and there isn't another Shell within 15-km of home so I'm running Petro-Canada 94 (E10) as it's the only 94 available near me.

datalog15.csv

[Pleides]

Ethanol is good for turbo cars, I’d not worry about that. Techron is Chevron/Texaco’s proprietary fuel additive package for their gasoline. You can buy it at Advance/NAPA/Autozone. Redline fuel injector cleaner contains a higher concentration of PEA which I’ve read from petrochemical engineers does help clean out injectors, but that’s beside the point.

 

How old are your injectors? My sidefeeds finally caved a few months ago due to bad o-rings and I went topfeed. I had some similar symptoms to you, mainly the smell of gas because they leaked.

[solidxsnake]

DAM, FLKC and FBKC all react to the same thing: the knock sensor. Depending on load/RPM, the car will either do nothing, or react with one of the three types of knock correction if the knock sensor is triggered. If the DAM changes at all (up or down), the ENTIRE FLKC table will be reset to 0 and start learning again. If it learns enough positive correction, the DAM will move up again and the table reset again, etc.

 

None of the knock correction parameters (DAM, FLKC, FBKC) respond to misfire (i.e. "roughness") events. If you log Knock Sum along with your three knock parameters, you'll see that the only time any of them change is when the knock sum increments.

[lagwagon]

DAM, FLKC and FBKC all react to the same thing: the knock sensor. Depending on load/RPM, the car will either do nothing, or react with one of the three types of knock correction if the knock sensor is triggered. If the DAM changes at all (up or down), the ENTIRE FLKC table will be reset to 0 and start learning again. If it learns enough positive correction, the DAM will move up again and the table reset again, etc.

 

None of the knock correction parameters (DAM, FLKC, FBKC) respond to misfire (i.e. "roughness") events. If you log Knock Sum along with your three knock parameters, you'll see that the only time any of them change is when the knock sum increments.

 

Thanks for the succinct explanation. I didn't understand that, even after reading that massive archive thread about the knock correction system.

 

Pleides, as far as I know, my injectors are original. I have wanted to do top feeds and TGV delete but then I need to get it tuned properly and all told I'd be looking at close to $2000CAD. Money I am also saving for a new engine (I'm at 253,000 kms). Am I right in assuming even just moving to top feeds would require a tune?

[xt2005bonbon]

Question about your log above: just to make sure, you did not reset the ECU prior to logging right? I am seeing some AFR learned values already, so I am guessing no.

[lagwagon]

Question about your log above: just to make sure, you did not reset the ECU prior to logging right? I am seeing some AFR learned values already, so I am guessing no.

 

Correct, no reset.

 

I did log this weekend with DAM, FKL and FKC included but trying to get a similar state as the previous misfiring won't log (2-3 minutes, long, gentle uphill at 100 km/hr). I can only get it to log for 20-30 seconds. I'll try to get those posted tonight. I could drop the fuel trims and maybe a couple other parameters to see if I can get it to log but with such an intermittent problem something could be missed, like a crazy avcs mismatch between left and right or something like that.

[xt2005bonbon]

OK. So, I asked that question because of your AVCS values: after looking at them, I am confused. We need someone who knows a lot about the AVCS angles. But what I know is that there is one AVCS per head, and that the reported angles should be very close to each other at all times. Second I have learned, at least from logging both of my cars, is that it will advance (i.e. increase AVCS angle) as you increase engine load. In my case, it peaks around 10deg. I can see yours peaks around 15-17deg. Yours also appear to stay in sync almost all the time, which is good.

However, what is confusing to me is that it appears that your AVCS angles stay around 15-17deg even when you cut fuel (e.g. AFR ~ 21.02 in your case). I am pretty sure on both of my cars, when engine load decreases or cut fuel, AVCS angles go back to zero (I need to double check). Also, I noticed when you got on it (100% throttle), your AVCS decreased to 8 or something. . I don't understand.

[Pleides]

Thanks for the succinct explanation. I didn't understand that, even after reading that massive archive thread about the knock correction system.

 

Pleides, as far as I know, my injectors are original. I have wanted to do top feeds and TGV delete but then I need to get it tuned properly and all told I'd be looking at close to $2000CAD. Money I am also saving for a new engine (I'm at 253,000 kms). Am I right in assuming even just moving to top feeds would require a tune?

 

You should just to the topfeed conversion with the new engine then. It is substantially easier to do like that.

[lagwagon]

OK. So, I asked that question because of your AVCS values: after looking at them, I am confused. We need someone who knows a lot about the AVCS angles. But what I know is that there is one AVCS per head, and that the reported angles should be very close to each other at all times. Second I have learned, at least from logging both of my cars, is that it will advance (i.e. increase AVCS angle) as you increase engine load. In my case, it peaks around 10deg. I can see yours peaks around 15-17deg. Yours also appear to stay in sync almost all the time, which is good.

However, what is confusing to me is that it appears that your AVCS angles stay around 15-17deg even when you cut fuel (e.g. AFR ~ 21.02 in your case). I am pretty sure on both of my cars, when engine load decreases or cut fuel, AVCS angles go back to zero (I need to double check). Also, I noticed when you got on it (100% throttle), your AVCS decreased to 8 or something. . I don't understand.

 

I think you might be on to something there, I seem to remember last time I logged a bunch of wot pulls that the advance got up to ~50°. I think I posted those logs somewhere on the board...I'll try to find them.

 

EDIT: I confused avcs with ignition timing, which I didn't log this time, and I didn't log avcs last time.

Edited November 22, 2021 by lagwagon

[lagwagon]

Here is the best log from this weekend with the knock parameters logged. I couldn't get a longer log, or one with WOT apparently, but at least you can see that the ecu is advancing timing under steady rpm/load.

 

I will try to get a wot log but honestly, the misfiring occurred for about 2-3 minutes and went away so I'm probably not going to get a log while it's happening. I can't see a mechanical issue being that transient under cruise conditions (other than maybe a dying fuel pump, or an injector) so I'm thinking it is probably an electrical issue.

datalog17.csv

[solidxsnake]

Single AVCS will typically peak in cruising ranges (low/medium load and RPM). Should be zero at idle/no-load, and will taper down from its peak value towards redline and higher load. The idea is that you want more intake cam advance in the cruising range to increase volumetric efficiency by introducing some scavenging. At higher RPM/load, you want to minimize intake/exhaust valve overlap to avoid losing uncombusted intake charge out the exhaust.

 

 

Stock AVCS tunes for later MY cars is in the ~30° range in the cruising area, from my memory.

[lagwagon]

From what I've read, for 2005 MY, peak avcs is 20° in the midrange. 07+ apparently had a different exhaust cam and could advance intake up to 40°.

 

I did catch the tail end of a misfire event this morning but can't pull the log at work. I was cruising at 60 km/hr in 4th gear (~2000 rpm). FBKC was at zero, then instantaneously jumped to -12 and started tapering down to zero within about 20 seconds. I think I caught it from -7 back to 0. I didn't feel or hear anything and had been at the same speed for about 30 seconds prior to the event and about 10 seconds after (will see exact numbers in the log).

 

I think this is either a minor electrical issue, or a broken ring land, but I'm probably just freaking out.

[lagwagon]

OK, the log that had the tail end of the misfire event was corrupted, along with about 8 other logs I took today.

 

Here are 4 logs (almost continuous driving/logging):

 

datalog35: take off from a light a do a mid throttle pull, big mismatch between L and R avcs angles, like 8-9°, this seems like it could be a major issue but is also one of the only times I've seen more than a 2° mismatch.

 

datalog36: wot blip, not much to see here I think

 

datalog37: short wot pull in 2nd gear downhill

 

datalog38: beginning of the log is going around a corner, then a longer wot pull in 2nd gear uphill

 

If you are looking at knock sum, I got stuck behind an accident for about 20-30 minutes and was stop and go that whole time which is why KS was already at 14. I have earlier logs from the drive and most of the knock events look to be starting off in 1st gear. From 17 to 20 was a from a stop light as well.

 

Sucks that I lost a bunch of logs that I think would've shown something useful but my AP lost comms twice on this drive and I assume that is when it happened.

datalog35 mid throttle pull avcs mismatch.csv

datalog36 wot blip.csv

datalog37 wot 2nd downhill.csv

datalog38 wot 2nd uphill.csv

[lagwagon]

Edited down log from earlier in the drive showing mismatch in avcs angle, consistently the left side is not advancing when it should.

 

Interesting, but doesn't seem related to any knock in any of these logs. I guess if it happens at higher load then it could. It looks like either the ocv or cam gear is sticking, the plunger is sticking or the oil pressure on the left head is too low at the engagement rpm.

datalog29 - avcs.csv

[All_talk]

Edited down log from earlier in the drive showing mismatch in avcs angle, consistently the left side is not advancing when it should.

 

Interesting, but doesn't seem related to any knock in any of these logs. I guess if it happens at higher load then it could. It looks like either the ocv or cam gear is sticking, the plunger is sticking or the oil pressure on the left head is too low at the engagement rpm.

 

I thought the ECU measured AVCS error, and if the requested angle was different from the measured angle by too much or for too long it would through a code. Not true?

[lagwagon]

I thought the ECU measured AVCS error, and if the requested angle was different from the measured angle by too much or for too long it would through a code. Not true?

 

I have looked through the MIL/DTC table in the FSM and haven't found anything related to AVCS angle, only circuit errors for the OCV (high or low voltage errors). I don't think it cares if the angle is wrong.

 

No updates on anything yet. Plan is order some crush washers and take the left near-OCV banjo bolt out and check the screen/filter (if there is one) and if it is clean, then replace the OCV. If it is dirty, I'll pull it out and see if anything changes. My car is a March 2005 build date so possibly I don't have a filter in the accessible end of the oil feed line.

 

I've got 90,000 kms (or 5 years) to go before I need to do the timing belt so I'd rather not have to replace the cam gear(s) right now but if this is causing the knock them I'll probably need to do it. I suppose there could be false knock from the plunger unsticking, or actual knock from the cams being out of sync.

[xt2005bonbon]

I have not taken the time to check your logs. But you could also quickly swap the OCVs and see what happens. If the angle gets stuck on the other side, then you know the OCV is bad.

But yeah, if angles are off or one of them is stuck, we usually suspect either a bad OCV or a possibly dirty filter on one of the banjo bolts. Also, the common codes are either P0011 or P0021.

[xt2005bonbon]

Also, I don't think anyone has asked: exactly which one of your cars has this issue? Is this car on a custom tune?

[lagwagon]

Also, I don't think anyone has asked: exactly which one of your cars has this issue? Is this car on a custom tune?

 

Its the 2005 GT 5MT. Its on a Cobb OTS stage 1 tune with 1° of timing pulled.

[lagwagon]

I have not taken the time to check your logs. But you could also quickly swap the OCVs and see what happens. If the angle gets stuck on the other side, then you know the OCV is bad.

But yeah, if angles are off or one of them is stuck, we usually suspect either a bad OCV or a possibly dirty filter on one of the banjo bolts. Also, the common codes are either P0011 or P0021.

 

I thought those codes are more related to a flow restriction after the OCV and cam gear that results in the cam being stuck at high advance, like when the filter right before the turbo is plugged.

 

If we assume that my right side is correct, then there is a restriction before my left OCV or cam gear and if we assume my left side is correct, then there is a restriction after my right side OCV or cam gear. I know my turbo has been replaced some time in the last 80,000 kms (5 years) so I assume there is no filter in the turbo feed and that my right side is correct and left side is incorrect.

 

I did the cold start, 2000 rpm hold and 3000 rpm hold test/initialization and consistently the left side is not advancing when duty cycle is applied, for about 5 time steps (sorry don't remember what the time step is in the logs), and then to get to the same advance as the right side it has 2-5% more duty cycle.

 

I do have logs of these tests but I didn't think there is any point in posting them as the next step is to start pulling the oil lines, checking filters and possibly swapping OCVs. I just need to get some time to grab new crush washers so I can actually do it and not end up with a leak.