Just another misfire/rough idle thread...

[birkhoff]

Misfire count.

 

It cannot be that it counts until it gets to some number and resets since we are reporting all sorts of different values at reset. It is events per time interval.

 

OP posted logs with misfire counts earlier in this thread. It resets 3 or 4 times during the log. Time interval between resets, reading from this log, is 7904 and 7954 msec for the first two full intervals. I didn't bother checking the others.

 

Anyone want to bet that the count is NOT per 8 second interval?

[birkhoff]

Have you tried any "live" tests when it is misfiring? Wiggle the #2 coil plug to see if it stops missing. Wiggle the #2 injector plug to see if it stops missing. Turn on the AC to raise the idle a little. Move the shifter from park, drive, reverse, etc. Just looking for ANY more variables

 

^+2 for that. OP has honed his senses so well that he can read the OBD codes with his mind. Try to make it misbehave with your hands! Just be careful where you put them while the engine is running.

 

Has anyone actually followed the FSM diagnostic procedure for the P30x codes? Unless I am reading it wrong, it concentrates on the lines and connectors for the injectors, not the coils. Lines for the coils also have a diagnostic procedure but it is in the 'no start' section around page 64. Weird.

 

Try 'massaging' the electrics on the #2 injector while you are at it, like heiche suggested.

Edited September 21, 2016 by birkhoff

[StkmltS]

Have you tried any "live" tests when it is misfiring? Wiggle the #2 coil plug to see if it stops missing. Wiggle the #2 injector plug to see if it stops missing. Turn on the AC to raise the idle a little. Move the shifter from park, drive, reverse, etc. Just looking for ANY more variables

 

Maybe, but it's been so long I can't remember if I have or not. I'll try before I leave work today.

 

P/N/D/R doesn't change anything because I'm 5mt... it happens in any gear with the clutch in, and it happens in neutral, at a stop, with the clutch in or out. Coasting in neutral (or in gear) on the highway with the clutch in or out yields zero misfires.

[xt2005bonbon]

So you're saying the roughness count is misses per... what?

Currently mine seems to be resetting to zero after anywhere between 2 and 30 misses.

I'm still thinking about it.

 

 

When I saw the counter increasing like crazy with a leaky injector, I could clearly see it was about 6 count increments per second.

But then what still confuses me is when you see a count of 1 or 2 in a given cylinder and the counter is stuck at that value for a short period of time. I am not sure what that means in this scenario... Maybe the ECU counted 1 miss at a particular time and then the counter stays at that value and is listening for more coming? If none, then counter resets to zero? I don't know.

[StkmltS]

This is a good discussion.

[xt2005bonbon]

It cannot be that it counts until it gets to some number and resets since we are reporting all sorts of different values at reset. It is events per time interval.

 

Just to be clear though, I know for a fact that the max value the counter can report is 99. If it reaches 99, it'll go back to zero right away and keep incrementing if needs be. It happened to me a couple of times with that freakin leaky injector .

 

Personally, if you see this happening, you are misfiring reaaaaal bad

[birkhoff]

Just to be clear though, I know for a fact that the max value the counter can report is 99. If it reaches 99, it'll go back to zero right away and keep incrementing if needs be. It happened to me a couple of times with that freakin leaky injector .

 

Personally, if you see this happening, you are misfiring reaaaaal bad

 

I bet your engine was just scared what you would do to it if it went into triple digits!

[xt2005bonbon]

It happened to both of my cars too . I've learned my lessons when installing injectors. 1. make sure you use superlube. 2. As you are installing the injector, you should hear a small 'pop' once properly seated. If no pop, chances of 99+ counts is pretty high .

[birkhoff]

I ALWAYS lube my injector before insertion. Sometimes I hear a small pop, sometimes not. . .

[heiche]

This just got real

[StkmltS]

It's about to get real in a couple minutes when I walk out of work to twist my coil pack and wiggle my injector.

[xt2005bonbon]

Calm down guys!

[ScottFW]

I had a gunky injector causing roughness counts in one cylinder that could be heard & felt at idle, but got no roughness counts or knock and it ran smoothly while driving.

 

I pulled the injector from that cylinder and did a DIY cleaning by letting it sit in a shot glass with some Sea Foam and then pulsing it with a 12V battery. That cured the roughness, but I went ahead and had my injectors professionally cleaned by Deatschwerks anyway, and I haven't gotten any roughness in the ~50,000 miles since then.

 

I should say that my injectors were not too crummy looking even before cleaning. Just a slight brown film/varnish on the nozzle end, nothing particularly alarming, but that's no indication of how dirty they may have been inside. Point being, unless your used OEM injector/s came with a receipt for a cleaning service, they could be just as bad.

 

Conceptually it made sense to me that a non-optimal or dribbly spray pattern is going to have a higher likelihood of manifesting itself at short pulse widths (idle) versus longer PWs under higher rpm & load conditions. I don't think a coil or plug would only cause misfires at idle and not under load, actually I think the opposite is more likely. And your wiring will be jiggling plenty when driving down the road, so that would not be my prime suspect for idle-specific issues.

[heiche]

Good job solving that issue.

 

However, I think OP swapped positions of his injectors and coils IIRC, but the misfire remained on cyl 2.

[xt2005bonbon]

Also. I had a failing coil pack on #3 that was causing a fairly consistent roughness count up to 3 in that cylinder at idle. I just changed it and the issue is gone. The coil pack also looked bulged on the outside. I *think* it is a bit of a common occurrence for a coil on #3, maybe due to the fact that it gets more heat than others. At least I know I've seen it before on the forum too.

[birkhoff]

I agree that injectors and coils that are having a hard time keeping up at low speed are unlikely to correct themselves under higher speeds or increased load. But I don't think we can say for sure the misfires are not happening at high speed as well.

 

There are bound to be limitations to the misfire detection system and there may be some engine speeds above which the sensors and ECU are simply unable to confirm a misfire. It may also be load related.

 

If this is true, at higher speeds/loads you are going to see the effect more in general loss of power and perhaps unburned hydrocarbons in the exhaust stream, the latter if the injection is happening but the ignition is not.

 

The fact that we often report misfires at low engine speeds/loads may say more about the detection system than the prevalence of misfires.

Edited September 21, 2016 by birkhoff

[StkmltS]

At first I thought the same thing, but...

 

When it's missing if I press the throttle and raise the rpm to say, 2500, it continues to detect misses, just at a faster pace.

[StkmltS]

I had a gunky injector causing roughness counts in one cylinder that could be heard & felt at idle, but got no roughness counts or knock and it ran smoothly while driving.

 

I pulled the injector from that cylinder and did a DIY cleaning by letting it sit in a shot glass with some Sea Foam and then pulsing it with a 12V battery. That cured the roughness, but I went ahead and had my injectors professionally cleaned by Deatschwerks anyway, and I haven't gotten any roughness in the ~50,000 miles since then.

 

I should say that my injectors were not too crummy looking even before cleaning. Just a slight brown film/varnish on the nozzle end, nothing particularly alarming, but that's no indication of how dirty they may have been inside. Point being, unless your used OEM injector/s came with a receipt for a cleaning service, they could be just as bad.

 

Conceptually it made sense to me that a non-optimal or dribbly spray pattern is going to have a higher likelihood of manifesting itself at short pulse widths (idle) versus longer PWs under higher rpm & load conditions. I don't think a coil or plug would only cause misfires at idle and not under load, actually I think the opposite is more likely. And your wiring will be jiggling plenty when driving down the road, so that would not be my prime suspect for idle-specific issues.

 

Your first sentence exactly describes my situation.

 

I've already swapped around my injectors and it didn't change anything. I even bought a small ultrasonic cleaner to see if that would help.

 

I like the way you're thinking about a non-optimal spray pattern causing more issues at low RPM/load than high RPM/load. I'm going to dig in to this a little deeper and see what the Internet has to say.

[xt2005bonbon]

Why don't you send all of your injectors to Deatshwerks for a cleaning (27$ per injector) preceded by a pre-test($5 per injector)?. If the pre-test results show that they are all in good shape, they will call you to let you know that cleaning is not required. That's what happened to me anyway about a month ago. I was pleasantly surprised. How many miles on them anyway?

[heiche]

also how did your empirical testing go last night? (wiggles and what-not)

[birkhoff]

At first I thought the same thing, but...

 

When it's missing if I press the throttle and raise the rpm to say, 2500, it continues to detect misses, just at a faster pace.

 

Low load.

 

As heiche describes it, the ECU is looking for slight changes in angular velocity, and then tries to match what it sees with a planned ignition event. If all cylinders are working hard and one takes a pause, it may be hard for the system to detect under the higher torque and angular momentum.

 

I do find it interesting that we typically only see misfires in some combination of low RPM and low load. Kind of hoping someone who actually knows the limitations on these systems will chime in. This is all pure conjecture on my part.

[birkhoff]

Why don't you send all of your injectors to Deatshwerks for a cleaning (27$ per injector) preceded by a pre-test($5 per injector)?. If the pre-test results show that they are all in good shape, they will call you to let you know that cleaning is not required. That's what happened to me anyway about a month ago. I was pleasantly surprised. How many miles on them anyway?

 

I'd be thinking in the other direction: change as little as possible and concentrate on one thing at a time. I sense we agree that if only one thing can be looked at, it should be electrical.

 

If you start pulling injectors, you may change the electrical and attribute it to the mechanical, when in fact it was the electrical. Does that make sense? I'm not sure I believe it myself!

 

There are multi-step diagnostics in the FSM for both injector and ignition electrics that involve a multimeter and a little time. Just because the dealer service places follow the FSM (I hope!) doesn't mean the FSM is dumb.

 

There is an end to this road that we all know, but don't want to say. If no external cause can be found, the engine has to come out and the head come off to look for a crack or other defect that was missed at rebuild time. Nobody wants to do that. Slow and systematic until there are no other options!

Edited September 22, 2016 by birkhoff

[xt2005bonbon]

yeah sure. one thing to check at a time.

 

In my case, I also had misfire in #2 and I knew the injectors were not at fault. But I have 141k on the car. So I thought it was a good time to send them for cleaning anyway.

[StkmltS]

There is an end to this road that we all know, but don't want to say. If no external cause can be found, the engine has to come out and the head come off to look for a crack or other defect that was missed at rebuild time. Nobody wants to do that. Slow and systematic until there are no other options!

 

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAH not gonna happen.

[heiche]

For giggles, if it's having another episode of misfiring at idle, can you unplug the driver-side OCV wiring connector? Just curious if misfiring stops (or starts) Edited September 22, 2016 by heiche