m60b40 missing, low idle, back firing

[RobertK]

You check your wire harness for possible shorts to the ICV?

Know anyone with a GT1 that can look at all the sensor read outs?

[JGood]

Swapped out the CCV, no change. So vacuum leaks can be 100% ruled out, I've replaced every single gasket and part on the entire intake system, and smoke tested it as well, there is not a single leak.

I ordered a set of rebuilt Bosch design III 19lb injectors. Maybe I have a leaking injector(s). If not, it's still a worthwhile upgrade for the spray pattern.

If that doesn't cure it, I'm going to find a known good ICV and try that. Maybe the two I have are shot.

This sucks!

[JGood]

Nope, don't have access to one.

Drove about 2 hours today. Got 100% repeatable results. While driving, if I coasted to a stop in any gear, letting the car engine brake, and the RPM's got below 1500 or so before I push in the clutch, it would then shut off. If I threw in the clutch before it got down below 1500, it would return to idle like normal.

Definitely a fuel injection/ignition issue. Sticking injector maybe?

I also have an o2 sensor code, just the passenger side though.

My new CCV just showed up, so I'll try swapping that.


Edit: Forgot to add, the backfiring is also consistent now. Any time I'm cruising along, and leave off the gas for a few seconds, then get back on the gas, it gives a fairly loud pop/backfire through the exhaust, it sounds more like a loud crack. Just one. I have no idea what would cause that... but I'm pretty sure it's made more noticeable by the exhaust leaks right after the headers, that's where I hear it the most, right under me. But the people who were in front and behind me on the way to the car meet said they could hear it occasionally as well.

[kristov]

Have you had it diagnosed with a proper BMW scanner?

[JGood]

Thank you Jean, greatly appreciated. I'll be in touch.


Went for a drive, I got it to shut off twice. It seems to be more tempted to shut off if while I'm decelerating to a stop, I don't put in the clutch until the RPM's are below 1500 or so. Almost like it's loading up with fuel as the RPM's are that low under deceleration load.

If I throw in the clutch above 1500 while decelerating to a stop, it will drop to idle, stay there, and coast to a stop no problem at all.

It was only a 10 minute drive though. I'm heading to the Bimmerzone meet today, 45 minutes away, so I'll be able to report back with better info hopefully.

[Jean]

Keep it for as long as you need it, no rush.

[dirty30]

Nice! Glad to hear it wasn't something you had any control over. Now get some sleep I'm sure you've been losing it over that damn thing.

[JGood]

Well, I may finally be able to put this thread to rest.

I threw in Jean's ECU, plugged in the o2 sensors, and fired her up. I let it warm up, gave it a few revs, and it didn't shut off. Went for a drive, it didn't shut off.

I can't even describe the relief I feel right now. I was starting to go insane trying to figure this problem out. I'm actually glad it turned out to be a flaky, and somewhat un-testable part, as opposed to something stupid that I overlooked.

I'd like to put a few miles on it and let the ECU adapt, before I'm completely confident that the issue is gone.

But still...


I'M SO F'IN HAPPY!!!!!!!!

[RobertK]

It really doesn't exhibit any symptoms of bad compression. Maybe I'm not doing a good job of describing the problem. With the o2 unplugged, it runs 100% perfect, except for a slightly jerky transition from on throttle to off throttle, and vice versa (at any RPM). If it wasn't for that jerkiness, I'd leave the o2's unplugged and say screw it. I did a 5th gear 1500 RPM pull, it makes awesome power even that low. It spins the 235's in 2nd gear and idles at exactly 500 RPM's, dead steady, all day. I could take a video, but a picture of the gauge with the needle sitting at 500 rpm's would be the same thing. It doesn't budge. I've left it idle for like an hour without a single blip or hiccup.

It only totally transforms to a shitty idle only when the o2 is plugged in. It has to be a mixture issue.

I'll test it for the hell of it, when I get a chance.

Does it sound like it is idling low or could it be possible that there is just a coding issue between the ECU and your cluster?

What's weird is when I rebuilt my S50 I drove it around during break in with no O2 sensor and it ran just as well as it did with it plugged in but you could smell that it was running a little rich. Idle and throttle reaction was just the same with or without the O2 plugged in as well.

I should have asked this from the very beginning. How long do you have to crank it to start it up?

[JGood]

Definitely interested. I did a bit of welding somewhat close to mine, and have been wondering if that could have damaged them. PM coming. Thanks a lot!

[dirty30]

Want another set of O2's to try? I have a pair of screw together style ones from the 740il I parted for my M60. I drove the car around for a couple hundred miles prior to taking it apart so I know they are good. PM me if you are interested. Just pay shipping that's all.

[JGood]

Screw-together style

[dirty30]

Does your harness have the screw in O2 connector or the push together style?

[JGood]

I've got one too if you need it.

404 is also OBD1 which I thought was before CAN bus.

Do you have the CEL code number?

Code 210

"CAN Interface, Trans. Intervention Version DME"

I really hate to sound like a broken record and I sincerely hope that I am wrong but it really scares me how you've just about described everything I experienced when I first installed my S50 (O2 sensor didn't make a huge difference). You're engine might be at the threshold of healthy compression on all but 1 or 2 cylinders. In my case I had 1 very unhealthy cylinder @30psi, 2 unhealthy cylinders @65~70psi and the rest were 95~120psi.

Even have a video of the low idle while the engine hunts to raise idle and when we rev it and slam the throttle shut it either shuts off or do the low~high fluctuation which got worse as the engine warmed up.

Do you have any videos are starting and idling it? I will try to find mine for comparison.

I know what its like to bang your head against the wall trying firgure out the little stuff when you are in the home stretch but do that compression test if even just for peace of mind. I avoided it for 2 days trying just about everything else just because I didn't want to know.

It really doesn't exhibit any symptoms of bad compression. Maybe I'm not doing a good job of describing the problem. With the o2 unplugged, it runs 100% perfect, except for a slightly jerky transition from on throttle to off throttle, and vice versa (at any RPM). If it wasn't for that jerkiness, I'd leave the o2's unplugged and say screw it. I did a 5th gear 1500 RPM pull, it makes awesome power even that low. It spins the 235's in 2nd gear and idles at exactly 500 RPM's, dead steady, all day. I could take a video, but a picture of the gauge with the needle sitting at 500 rpm's would be the same thing. It doesn't budge. I've left it idle for like an hour without a single blip or hiccup.

It only totally transforms to a shitty idle only when the o2 is plugged in. It has to be a mixture issue.

I'll test it for the hell of it, when I get a chance.

[RobertK]

PM me your address I can mail you my 404 to try.

I've got one too if you need it.

404 is also OBD1 which I thought was before CAN bus.

Do you have the CEL code number?

Summary of the current (major) issues:

-With o2 sensors unplugged, car idles dead steady at 500 rpm's, has full power, and runs great overall, except the on/off throttle transition, it's jerky and feels like the engine is slow to respond.

-With o2 sensors plugged in, I can start the car, it will idle at about 500 rpm but will go up and down the tiniest bit, maybe 50 rpm's. It will do this for hours without any major stumbling. When I give it a little throttle, and it struggles to rev. I give it a lot of throttle and it revs perfectly. As soon as I leave off the throttle though, it goes down to idle, and will either immediately shut off, or rev up and down from 400-1000 rpm's a few times, then shut off. I restart it, steady at about 500 rpm's again.

I really hate to sound like a broken record and I sincerely hope that I am wrong but it really scares me how you've just about described everything I experienced when I first installed my S50 (O2 sensor didn't make a huge difference). You're engine might be at the threshold of healthy compression on all but 1 or 2 cylinders. In my case I had 1 very unhealthy cylinder @30psi, 2 unhealthy cylinders @65~70psi and the rest were 95~120psi.

Even have a video of the low idle while the engine hunts to raise idle and when we rev it and slam the throttle shut it either shuts off or do the low~high fluctuation which got worse as the engine warmed up.

Do you have any videos are starting and idling it? I will try to find mine for comparison.

I know what its like to bang your head against the wall trying firgure out the little stuff when you are in the home stretch but do that compression test if even just for peace of mind. I avoided it for 2 days trying just about everything else just because I didn't want to know.