COBB/MHD users, help me out

[CarJunkie]

I want you to monitor something for me. Please set your guages to watch Lambda (bank 1) and Lambda (bank 2) and tell me what you see when you coast in gear above 1500 RPM's.

When I first installed the Cobb, I was monitoring Lambdas and saw that the Lambdas QUICKLY shot up to 235 (max value) when coasting in gear above about 1500 rpms, indicating that fuel had been shut off. I started watching them again this week after getting a new tune from my tuner and was surprised to see that the lambda's NEVER reach 235, they shoot up to about 160-200 and bounce around there. The "Max value" will often catch a brief hit to 235, but the actual reading never stays there which it used to do. I don't think this is a tune issue. To me it suggests that at least 1 injector on each bank is still spitting out some fuel.

Thoughts?

Background:
I have been troubleshooting a long crank/sputtering start issue for a while. The symptms improved somewhat after running a fuel system cleaner. I have since had valves cleaned, replaced spark plugs and coils with appropriate LVS reset, and have had the car to the dealer where LPFP, HPFP and fuel injectors all "passed."

The issue now mainly occurs if I start the car after it has sat for 1-2 hours. Cold start is good, immediate restart is good, but a partial cool down results in difficulty starting. It is not as bad as it was before replacing coils and plugs, but still happens frequently.

I suspect I have leaking injectors, which flood the engine, which is why there is a relation to how long it has sat. Long enough for pressure in the lines to bleed off through a few bad injectors, but not long enough for that gasoline to drain out of the cylinder.

Thread here:
http://www.1addicts.com/forums/showthread.php?t=1277852

[GimmeanM]

I just got a Cobb and ran a log on stage 0 to see what everything looks like. I have the file I can send you. It was a 4th gear pull from 2k to 6k and will have some time with 0% throttle after 6k. Happy to send it to you to compare. PM me your email address.
-Dave

[lightning]

Originally Posted by CarJunkie

I want you to monitor something for me. Please set your guages to watch Lambda (bank 1) and Lambda (bank 2) and tell me what you see when you coast in gear above 1500 RPM's.

When I first installed the Cobb, I was monitoring Lambdas and saw that the Lambdas QUICKLY shot up to 235 (max value) when coasting in gear above about 1500 rpms, indicating that fuel had been shut off. I started watching them again this week after getting a new tune from my tuner and was surprised to see that the lambda's NEVER reach 235, they shoot up to about 160-200 and bounce around there. The "Max value" will often catch a brief hit to 235, but the actual reading never stays there which it used to do. I don't think this is a tune issue. To me it suggests that at least 1 injector on each bank is still spitting out some fuel.

Thoughts?

Background:
I have been troubleshooting a long crank/sputtering start issue for a while. The symptms improved somewhat after running a fuel system cleaner. I have since had valves cleaned, replaced spark plugs and coils with appropriate LVS reset, and have had the car to the dealer where LPFP, HPFP and fuel injectors all "passed."

The issue now mainly occurs if I start the car after it has sat for 1-2 hours. Cold start is good, immediate restart is good, but a partial cool down results in difficulty starting. It is not as bad as it was before replacing coils and plugs, but still happens frequently.

I suspect I have leaking injectors, which flood the engine, which is why there is a relation to how long it has sat. Long enough for pressure in the lines to bleed off through a few bad injectors, but not long enough for that gasoline to drain out of the cylinder.

Thread here:
http://www.1addicts.com/forums/showthread.php?t=1277852

Hey CarJunkie,

it sounds like leaky injectors, i had an issue with this a long time ago as well but it was solved after changing my injectors & my Lambda/O2 sensors.

[CarJunkie]

Originally Posted by lightning

Hey CarJunkie,

it sounds like leaky injectors, i had an issue with this a long time ago as well but it was solved after changing my injectors & my Lambda/O2 sensors.

Interesting. Were the O2 sensors bad, or changed as a precaution?

[CarJunkie]

Originally Posted by GimmeanM

I just got a Cobb and ran a log on stage 0 to see what everything looks like. I have the file I can send you. It was a 4th gear pull from 2k to 6k and will have some time with 0% throttle after 6k. Happy to send it to you to compare. PM me your email address.
-Dave

That was VERY helpful. When you lifted, the time from throttle position going to 0 to Lambda (bank 1) hitting 235.2 was less than 0.8 seconds and it stayed pegged at 235.2 as you coasted from 5800 rpm down to 3600 rpm.

My logs show the same behavior last August. I haven;t logged it currently, but I have the guages showing on the AP and can see when driving that they never go to 235.2 and stay there.

I see new injectors in my near future. I hope BMW will pay for them.

[GimmeanM]

Originally Posted by CarJunkie

That was VERY helpful. When you lifted, the time from throttle position going to 0 to Lambda (bank 1) hitting 235.2 was less than 0.8 seconds and it stayed pegged at 235.2 as you coasted from 5800 rpm down to 3600 rpm.

My logs show the same behavior last August. I haven;t logged it currently, but I have the guages showing on the AP and can see when driving that they never go to 235.2 and stay there.

I see new injectors in my near future. I hope BMW will pay for them.

Excellent! Happy to help.

[CarJunkie]

Injectors were replaced yesterday under warranty, also replaced the HPFP. The Lambda's now shoot right up to 235.2 on both banks when coasting in gear, within about a half second. This occurs at any rpm above about 1000 rpm.

With the leaky injectors, they would oscillate near 200, but never max out and stay there. The higher the rpm, the higher the lambda's would go. This is worth noting, because chances are we will all have this problem eventually and those with the ability to monitor lambda's will be able to see an early warning sign.

[BQTuning]

There is perhaps an efficiency issue. More likely you need more ignition timing added to that area load/rpm on the mapping that you are leaning out at.

[BQTuning]

Forgot to add

When decelerating, post shifts or letting off from going WOT this event will also occur which is normal and depends on how the timing tables are setup

http://datazap.me/u/buraq/log-148989...=3-15-16-22-28

In the event of cruising or coasting with a steady load, you will sometimes see AFR spike . You will see this most of the time on modded cars with higher octane than 91 ACN

When you mod your car your making it "more" efficient, so running the stock timing table may fall short, and will need optimizing.

Couple of things that will show that your not running efficient enough for the "fuel" that your are running.

Black ooze coming out of the tail pipes and on drive ways and AFR spike during cruise or coasting.

If your getting black ooze but no AFR spikes during cruise or coasting is more likely from being completely catless. Its a challenge to resolve especially when the weather changes.

Sometimes it maybe hardware related also, leaking injector or bad O2 sensor

[CarJunkie]

Originally Posted by ********

Forgot to add

When decelerating, post shifts or letting off from going WOT this event will also occur which is normal and depends on how the timing tables are setup

http://datazap.me/u/buraq/log-148989...=3-15-16-22-28

In the event of cruising or coasting with a steady load, you will sometimes see AFR spike . You will see this most of the time on modded cars with higher octane than 91 ACN

When you mod your car your making it "more" efficient, so running the stock timing table may fall short, and will need optimizing.

Couple of things that will show that your not running efficient enough for the "fuel" that your are running.

Black ooze coming out of the tail pipes and on drive ways and AFR spike during cruise or coasting.

If your getting black ooze but no AFR spikes during cruise or coasting is more likely from being completely catless. Its a challenge to resolve especially when the weather changes.

Sometimes it maybe hardware related also, leaking injector or bad O2 sensor

Now I understand the e-mail this morning, I hadn't seen this yet, but need to clarify . . . I am not seeing AFR spikes when on the throttle, cruising at constant load.

What I am describing above in this thread "coasting in gear" is with Accelerator Pedal at 0% with the car in gear, so the momentum of the car is turning the engine. The DME shuts off fuel, which means air just flows through the engine. The lambda's should max out since there is no oxygen being consumed. I believe that is normal, and it is what happened when I first started using the Cobb and playing around with OTS maps, and when we first started working on the tune.

After replacing the injectors, the car is now is back to normal, fuel appears to promptly shut off when lifting off the throttle and coasting in gear, Lambda's go from target AFR to 235.2 in about a half second, like they did when I first got the Cobb. It was only as the injectors were failing that the lambda's stopped maxing out, and I was wondering if anyone else had seen that and used as evidence for warranty coverage. (hence this thread) Fortunately my injectors finally failed testing at the dealer and got replaced.

With failing injectors, I had many other symptoms (cloud of smoke when first going WOT, cloud of smoke when revving from idle, tailpipes quickly soiled, rough idle, long cranks on start-up, running like crap at low rpm's when cold) all of which have now resolved with new injectors.

I'll send you logs later. My theory is that the timing corrections we always saw on cyl 2 and cyl 4 were related to innacurate fueling, and we may be able to dial it in a little better now, possibly a little leaner.

Thanks for being so attentive!