[Velocity26]

Here is my misfire story ...

I am FBO, no meth, Cobb stg 2 with fresh spark plugs.

I am passing a car in traffic and feel a shudder, similar to traction control kicking in, but no light or indication of slip. No CEL.

The car starts in the morning with a slightly rough idle that clears with a throttle blip. I ran some logs today and am not clear on the cause. I got the following messages (codes) Cyl 1 misfire, cyl 3 misfire, cyl 5 misfire, cyl 2 misfire, cyl 4 misfire, random multiple cyl misfire, fuel pump plausibility, and getting some lambda codes.

My LPFP shows a target of 72psi and it holds a solid 70 psi actual on cruise. On boost, the actual pressure starts a violent oscillation from 48 to 80psi, but it spends the majority of the time around 60 psi. As soon as the boost is cut, the pressure returns to a solid 70.

The HPFP log is not so simple since the target constantly changes. When I step into the throttle, the target pressure rises from 760 to about 2400 and the actual is very close to requested. As the boost peaks, the actual pressure is about 500psi below target (2300req-1800act) and that is where I feel the shudder. As soon as I back off, boost tapers off, and actual pressure returns to match the target. The HPFP pressures are smooth, not oscillating up and down wildly like the LPFP readings.

I checked out the fuel trims around the same time and the bank 2 STFT reach 34 and are steady under boost.

Since the HPFP cannot influence the LPFP, I am suspecting the LPFP and starving the HPFP for fuel. They can both be bad, but I do not like what I see on the LPFP log.

Forgive how short the logs are, I am not comfortable staying in the boost with it missing like this, I am sure that I could damage a piston if I push it hard.

Which do you think is bad, or both?

Thanks

[NA55]

how old are your plugs and coils?
what type of gas are you running?

post up logs so we can see whats going on..

[Velocity26]

I am running on straight 93, no Ethanol. The plugs are 2 weeks old and the coils are original with 39k miles. A few weeks ago I had a hard misfire on #2 and it would CEL and reduce power. I swapped the coils and the misfire stayed with #2, so I replaced the plugs and the misfire went away.

I only logged a few items, HPFP, LPFP, targets, and fuel trims. Since the misfires were not related to any cylinder, I did not include the other items.

Here are 2 logs that I imported to xls for graphing, just remove the .txt and it should open in Excel.

I appreciate the help.

[boostaholic786]

looks like your LPFP is having some issues keeping up...What fuel are you running and if your running E85, lower the content and see what happens...

[Velocity26]

Running straight Shell 93 with NO E-85 mix.

[Jeff@TopGearSolutions]

Post logs to datazap.me

I want to say my LPFP pressure look exactly the same.

[Velocity26]

Jeff,
Uploaded what I have, have to find the major problem before I can run some full pull logs. Afraid that I will hurt the motor if I try to push through the miss. It is likely a lean-out.

http://datazap.me/u/velocity26/

[Chris@BoostConcepts]

Low pressure pump should never go that low on straight 93 I saw a few valleys in the 50's... I would say it about time for a new pump. Old one is getting tired.

Maybe jump up to a upgraded unit to make it worthwhile.

Chris

[jtswole]

On 100% e85 my lpfp stays at 60-80

[Velocity26]

My logic, please correct me if I am wrong, is that the if the HPFP is going bad, it would have NO effect on the LPFP pressures except for possibly making it easier to maintain pressure since the flow is lower. However, if the LPFP is going bad, it could starve the HPFP and make it appear to be failing when it is simply starved for fuel. I would rather doubt that they would both fail simultaneously, so I plan to replace the LPFP with a Stg 2 fuel-it and try again. If the HPFP problem continues, I will try to have the dealer replace it under the extended HPFP warranty.

[Velocity26]

As Jeff predicted, the oscillations on the LPFP were not really indicative of a bad pump. I installed a Fuel-It Stg 2 pump (thanks Jeff) and still have oscillations in the pressure. They seem more centered on the pressure requested line, but there are still oscillations on boost.

The HPFP pressure sag has not changed a bit and I am betting that is the real problem. I can see times where the actual pressure is 500psi below the requested pressure and it does not correct until the fuel demand is reduced. I also see where the STFT are often over 30 which indicates that the ECU is doing all that it can to enrich the mixture.

Can anyone think of anything I can test short of replacing the HPFP?

I am really scared of pushing the engine (to test it) when I can feel it going lean. I am not sure how much of this it will tolerate before it damages a piston.

[Jeff@TopGearSolutions]

Originally Posted by Velocity26

As Jeff predicted, the oscillations on the LPFP were not really indicative of a bad pump. I installed a Fuel-It Stg 2 pump (thanks Jeff) and still have oscillations in the pressure. They seem more centered on the pressure requested line, but there are still oscillations on boost.

The HPFP pressure sag has not changed a bit and I am betting that is the real problem. I can see times where the actual pressure is 500psi below the requested pressure and it does not correct until the fuel demand is reduced. I also see where the STFT are often over 30 which indicates that the ECU is doing all that it can to enrich the mixture.

Can anyone think of anything I can test short of replacing the HPFP?

I am really scared of pushing the engine (to test it) when I can feel it going lean. I am not sure how much of this it will tolerate before it damages a piston.

Glad I could help you out on the Fuel it Stage 2 LPFP Upgrade.

I'm going out on a limb here but based on your HPFP data, it would seem like maybe it's tired.

Now I don't know for sure since this is the first time I've really analyzed HPFP data but it doesn't look right.

I'd consider getting in touch with someone that looks a lot of datalogs and tunes, someone like Wedge.

Also, you said you can actually feel the car lean out? You should be throwing lean codes if your AFR are not in check or at least some glow codes if you are knocking. You are misfiring though?

Have you any old datalogs of your vehicle showing air fuel ratio?

I noticed your STFT are looking for a lot of fuel too.

[Velocity26]

Jeff,

You can feel the car surging on high boost, as if you were peddling the throttle. As soon as I feel the car start to buck, I back off the throttle pretty quick. If I push it a little, I will get the "random multiple cyl misfire, Lean bank 2, and fuel pump plausibility" codes.

I will see if it will log the A/F ratio and pull a log on the way home.

Misfires do not bother me, but knocks and lean outs will eventually eat expensive parts.

[Jeff@TopGearSolutions]

Originally Posted by Velocity26

Jeff,

You can feel the car surging on high boost, as if you were peddling the throttle. As soon as I feel the car start to buck, I back off the throttle pretty quick. If I push it a little, I will get the "random multiple cyl misfire, Lean bank 2, and fuel pump plausibility" codes.

I will see if it will log the A/F ratio and pull a log on the way home.

Misfires do not bother me, but knocks and lean outs will eventually eat expensive parts.

OK well if you are getting the lean bank 2 codes and the fuel pump then I really think your HPFP is done, especially with the way it can't meet target.

Any long cranks at start up? That used to be the way of knowing if the HPFP was bad back in the 07-09 era but HPFP can still be bad without doing that.

Do you happen to know your injectors index?

[Velocity26]

From time to time, I can have a longer than normal crank, first thing in the morning. When I get the long crank, it will usually have an rough idle for several seconds, until I rev it, then it will clear and stabilize.

I may have a weak fuel injector in bank 2, but it is not bad enough to cause individual cylinder codes. Bank 1 is only slightly richer than bank 2 and the STFT are over 30 there too.

[Jeff@TopGearSolutions]

Originally Posted by Velocity26

From time to time, I can have a longer than normal crank, first thing in the morning. When I get the long crank, it will usually have an rough idle for several seconds, until I rev it, then it will clear and stabilize.

I may have a weak fuel injector in bank 2, but it is not bad enough to cause individual cylinder codes. Bank 1 is only slightly richer than bank 2 and the STFT are over 30 there too.

Definitely sounds more and more like the HPFP for sure.

You should consider getting all 6 injectors too just to get that all up to task.

[Velocity26]

I have been hooking up the Cobb unit every morning, to monitor the HPFP during start-up, and the car has been starting fine, and idling smoothly every day. On the start-up map, the fuel pressure requested is about 2500psi and a pump can achieve that within a second. As the car warms up, the pressure is gradually lowered to 725 (at idle).

This morning I had the longer than usual crank, followed by the erratic idle, and I had the Cobb in hand to see what was happening. The LPFP built and was holding the 72psi, when I started the engine, the pressure was fluctuating from 100psi to 350psi and the car was barely idling. After several seconds of watching it struggle, I blipped the throttle and the pump seemingly caught prime and shot up to 2500psi instantly and the engine idled smoothly. This is pretty much what it has always done when the pump is having a bad morning.

In most other accounts I have heard, the pump usually fails completely soon after the symptoms begin to surface. This pump has been "failing" for a while now, but it does not seem significantly worse than it has been for a while.

Time to start looking for a new HPFP.

[Jklad]

Ok, this sounds like exactly why I was experiencing for almost a year with no damn codes to help me. Long story short, it was my hpfp. Injectors were fine.

I was having occasional (1-3 times a week) rough idle during cold start, which would then even out after 3-9 seconds. The Ron would dip and the car would sound like it was gonna die, and some times I would lightly rev and it would settle.

After 8 months of this shit a code for hpfp finally popped up. The local Bmw would not replace my hpfp for this code per the extended warranty. So I had some friends who are techs diagnose the lpfp was ok and the got the hpfp swapped at their dealership under warranty. Problem went away immediately with the new pump.

[Velocity26]

I agree, it sounds exactly the same.

I am in the zone where I could have the HPFP and injectors handled under warranty, if I wanted to go through their hassle. I might just buy the HPFP and install it myself and apply for reimbursement from BMW.

[Nonecure]

I have the same misfire issues and my HPFP looks much worse than yours. After replacing it the new one looks just the same. I'm not saying that a new HPFP wouldn't fix your problem, but it didn't help me.

.

[Velocity26]

I was reading a post where one of the repair shop had a car like ours and diagnosed it to be the HPFP failing. They replaced the fuel pump and had the exact same problem. They diagnosed it again and everything came back to it being a HPFP problem. They replaced it again and solved the problem.

I hear that there are not any new high pressure fuel pumps available, even the BMW dealership sells rebuilt pumps and boxes them as new. There is always a chance that the pump you received was just as bad as the one you took out. There is no way that your fuel pressure should consistently be 2,000 psi below the requested pressure and there not be a problem with the pump.

What do your Short Term Fuel Trims look like when the pressure sags like that?

What about your air/fuel ratio?

[Nonecure]

I never heard that before, but it makes sense. I guess I need to replace it again. I am surprised that the new pump was just as bad as the old one.

Below are logs I took before and after the pump replacement. I don't always get a misfire, so the 3rd gear pulls were ok. The last log I got a misfire.

Before new pump 3rd gear pull
http://www.datazap.me/u/nonecure/log...3&zoom=369-430

After new pump 3rd gear pull
http://www.datazap.me/u/nonecure/log...3&zoom=299-349

Misfire during general driving
http://www.datazap.me/u/nonecure/log...12-13-16-17-28