[turbo6justin]

I am out of my mind on this car. It is a basic bolt on MHD2+ running 93 octane. When it is cold it runs very rough, idle bounces all over. sometimes stalls. The colder it is the worse it is. Under 32f it is extremely rough, closer to 0f and it is hard to keep running. I have been fighting this for two years now and am out of ideas. Once it gets past the first minute or 90 seconds it warms up it runs great and fast and all that jazz. When I got it I started going through everything. I had a slightly sooty startup and had index 6 and 8 injectors. I bought 3 used index 12's threw them in with no change. Then bought 6 different index 12's from Island Road on here. No real change. After that I didn't really drive it much. It's winter again and I am tearing into this again. MY fuel pressures have always been good and no codes but I tried the cheep osias HPFP, first pump dead, second replacement pump also dead. Learned my lesson and bought a new HPFP from FCP, installed and no change. Before that I spent a week trying different combinations of the 6 index 6 and 8 injectors and 9 total index 12 injectors I have (all coded in of course), no real change or pattern. I have a new walbro 450 lpfp as insurance in the tank as well. Again no trouble codes even while it is missing, and fuel pressures have always been good. I reverted back to stock tune on the MDS, no change, updated to the v10.0 tune from MHD, no change. I can't keep buying injectors and hoping for different results.

This is a 3-28-2008 build but I pulled and looked and it apparently has a MSD81. The plugs are 1 step colder Bosch gapped about .021, fired by eldor coils. Walnut blasted, all those things. The car was owned by an older dentist before me, had dealer service, and I went through everything.

2 years in and I have barely driven it, avoid it all together in the winter and generally despise it. When it is summer or warmed up though... I fall in love.

Here is a video of a 25 deg start

Any ideas, I am out of my mind, time, and money for this one.

[RnmEvo9]

[Saif2018]

Originally Posted by turbo6justin

I am out of my mind on this car. It is a basic bolt on MHD2+ running 93 octane. When it is cold it runs very rough, idle bounces all over. sometimes stalls. The colder it is the worse it is. Under 32f it is extremely rough, closer to 0f and it is hard to keep running. I have been fighting this for two years now and am out of ideas. Once it gets past the first minute or 90 seconds it warms up it runs great and fast and all that jazz. When I got it I started going through everything. I had a slightly sooty startup and had index 6 and 8 injectors. I bought 3 used index 12's threw them in with no change. Then bought 6 different index 12's from Island Road on here. No real change. After that I didn't really drive it much. It's winter again and I am tearing into this again. MY fuel pressures have always been good and no codes but I tried the cheep osias HPFP, first pump dead, second replacement pump also dead. Learned my lesson and bought a new HPFP from FCP, installed and no change. Before that I spent a week trying different combinations of the 6 index 6 and 8 injectors and 9 total index 12 injectors I have (all coded in of course), no real change or pattern. I have a new walbro 450 lpfp as insurance in the tank as well. Again no trouble codes even while it is missing, and fuel pressures have always been good. I reverted back to stock tune on the MDS, no change, updated to the v10.0 tune from MHD, no change. I can't keep buying injectors and hoping for different results.

This is a 3-28-2008 build but I pulled and looked and it apparently has a MSD81. The plugs are 1 step colder Bosch gapped about .021, fired by eldor coils. Walnut blasted, all those things. The car was owned by an older dentist before me, had dealer service, and I went through everything.

2 years in and I have barely driven it, avoid it all together in the winter and generally despise it. When it is summer or warmed up though... I fall in love.

Here is a video of a 25 deg start

Any ideas, I am out of my mind, time, and money for this one.

Have you checked to see if any codes are present when it's running rough?

Walnut blasting?

[Soden82]

vacuum leak somewhere? Cracked VC? Loose vacuum line? Cracked intake manifold? Bad PCV valve?

If it goes away after cold start, it generally means that unmetered air is getting in and the ECU can't compensate for it and it runs rough until closed loop occurs and the o2 can fluctuate AFR values to compensate.

[BSM n54iS]

You mean 1 step colder NGK's? Put the OEM bosch plugs back in

[turbo6justin]

Okay in order here, it was 10ish F tonight, no codes pop up during the first minute of run time. I kept switching back into the codes part of the MDS app and nothing at all.

Valve cover was the last service before I got the car and has about 10,000 miles on it. The valve cover was replaced with a new valve cover not just the gasket. I can hook up a smoke machine ( I assume from the BOV is easy) and see but the lines actually look pretty good. I was repainting the vacuum canister bracket yesterday and noticed the vacuum lines were in good shape. I really doubt the manifold is cracked, smoke should show that as well. I do have a catch can off the PCV/back of the valve cover, gets a little film but no real oil, water, or volume of anything.

It has Bosch ZR5TPP33 with less than 1000 miles on them.

[335i54n]

what do the logs say, does it affect both banks? I would reaffirm the basics with a compression test 1st and since you are there you can test the injector for leakage and I would revert to oe plugs. you can remove the front 02 and try a cold start to check for plugged cats

[Saif2018]

Originally Posted by turbo6justin

Okay in order here, it was 10ish F tonight, no codes pop up during the first minute of run time. I kept switching back into the codes part of the MDS app and nothing at all.

Valve cover was the last service before I got the car and has about 10,000 miles on it. The valve cover was replaced with a new valve cover not just the gasket. I can hook up a smoke machine ( I assume from the BOV is easy) and see but the lines actually look pretty good. I was repainting the vacuum canister bracket yesterday and noticed the vacuum lines were in good shape. I really doubt the manifold is cracked, smoke should show that as well. I do have a catch can off the PCV/back of the valve cover, gets a little film but no real oil, water, or volume of anything.

It has Bosch ZR5TPP33 with less than 1000 miles on them.

Does turning on cold start noise reduction using MHD make any difference?

I would have stuck with OEM 3 pronged plugs, there's no need for colder plugs until you go past stage 2+

[turbo6justin]

What should I be looking at on the logs? The O2's are matched up, no timing corrections, everything looks normal to me. I already had cold start noise reduction turned on, I turned it off for this mornings cold start and I think it made it marginally worse. I stalled a few times since I didn't have my foot on the pedal to keep it alive. Something I have noticed is before it settles down there is virtually no 'normal' exhaust from the tailpipes. It will be a little black when it is really spitting and trying to stall. Starting any car in 10 degree weather will produce a fair amount of white water vapor, normal emissions, etc. That isn't happening which tells me it is definitely not getting enough fuel or burning it.

I have downpipes so no cat.

I have a set of Bosch ZGR6STE2 3 prong plugs that were in for about a month, I kind of like the idea of throwing those back in. I have changed everything fuel related a few times now with no real changes, makes sense to take a look at spark for at least a minute. I had put stock plugs in as a course of normal new vehicle maintenance, installed the MHD tune and the first drive as soon as I hit boost it started misfiring. Threw some eldor coils and tightly gapped 1 step colder plugs and everything misfire under boost wise was good. I might open the gap back up on those plugs or throw the 3 prongers back in for a bit to see if there is a difference. It's worth a few minutes and it's free.

I have run a compression test since this all started with good results.

Anyone else wish they had started making tick marks on the cowl every time they removed it. I should put the freakin thing on with zeus clips.

Thanks for the ideas!

[Soden82]

LPFP primes and holds pressure when the car is unlocked?

[turbo6justin]

LPFP primes and holds pressure and maintains 70+ psi @ wide open.

[ab987]

I agree with soden82, I think you either have some vacuum leak somewhere or maybe a valve cover that isn't sealing properly. What do your AFR values look like on a cold start when it does this? Can you take a quick log?

[335i54n]

check everything and compare it to when it does runs well and at different rpms. modern cars are pretty smart, enough cycles of it running like should set some type of code to direct you

if you do the plug, good to unplug the injectors and crank for 15sec and smell for fuel leak also

[turbo6justin]

I have a few logs, I can't figure out how to share them though. The 02's are pretty locked together at about 15:1 when it starts surging and trying to stall they go leaner and diverge from themselves, not always but the most recent log shows more difference bank 1 to bank 2. Once it settles down they hover around 14.7 like they should.

Through this whole years long ordeal I have not gotten any codes specific to this issue, or anything popping up during this bucking/stalling warm up.

I am still skeptical of anything valve cover related, it's newish, no leaks, no sucking sounds.

[ab987]

Originally Posted by turbo6justin

I have a few logs, I can't figure out how to share them though. The 02's are pretty locked together at about 15:1 when it starts surging and trying to stall they go leaner and diverge from themselves, not always but the most recent log shows more difference bank 1 to bank 2. Once it settles down they hover around 14.7 like they should.

Through this whole years long ordeal I have not gotten any codes specific to this issue, or anything popping up during this bucking/stalling warm up.

I am still skeptical of anything valve cover related, it's newish, no leaks, no sucking sounds.

Upload your log to data zap if you can. I had similar behavior when I swapped my O2s to test a bad one, the AFRs just diverged and diverged until the car died (understandably so)

[turbo6justin]

I have a couple logs from the last few days on there. My user name is turbo6justin.

Does that work to find them??

[335i54n]

ez way to check, run a can of brake cleaner over the engine and see if the engine react via trims, sound and rpm changes and open the oil cap also and see how the car reacts.

if you are sure all the repairs are done correctly and mechanically sounds, look at your electronics sensor/computers

[turbo6justin]

Well, that didn't work. Swapped the plugs back to the stock 3 prong style today and it started as horribly as ever. The 1 step colder plugs I pulled out were dark and sooty but that's to be expected, the last 15 starts have been stalling and bucking and I never drove it after that. None of the plugs smelled like fuel or were wet. I also ran around with a can of carb cleaner (flamable kind) and didn't see/hear anything real remarkable. I have never really liked that test much, way back in the carburated days it seemed to work but my experience is it has to be a pretty big leak to really notice it. That being said I sprayed down all the usual suspects with no results. I did spray some in the BOV line and it did idle up so at least the idea works. It is my thought that a big enough vac leak to cause these problems would be more obvious. I have no boost related codes, never have either too high or too low. The intake had new gaskets when I did the walnut blasting a few 1000 miles ago as well as the TB and pretty much anything else I touched. While it is running if I open the oil fill nothing real remarkable either, no strong suction to pull the cap back down, no change in idle.

I will probably do a proper smoke test tomorrow.

[rjahl]

Originally Posted by turbo6justin

Well, that didn't work. Swapped the plugs back to the stock 3 prong style today and it started as horribly as ever. The 1 step colder plugs I pulled out were dark and sooty but that's to be expected, the last 15 starts have been stalling and bucking and I never drove it after that. None of the plugs smelled like fuel or were wet. I also ran around with a can of carb cleaner (flamable kind) and didn't see/hear anything real remarkable. I have never really liked that test much, way back in the carburated days it seemed to work but my experience is it has to be a pretty big leak to really notice it. That being said I sprayed down all the usual suspects with no results. I did spray some in the BOV line and it did idle up so at least the idea works. It is my thought that a big enough vac leak to cause these problems would be more obvious. I have no boost related codes, never have either too high or too low. The intake had new gaskets when I did the walnut blasting a few 1000 miles ago as well as the TB and pretty much anything else I touched. While it is running if I open the oil fill nothing real remarkable either, no strong suction to pull the cap back down, no change in idle.

I will probably do a proper smoke test tomorrow.

Maybe I missed it but have your tried flashing back to stock? Perhaps it's something MHD related?

[turbo6justin]

I have tried V9 which is what has been in there for the last year+. Back to stock, then V10. All are the same.

[turbo6justin]

After the frustration of the afternoon, I took it out to get gas and hoon around a bit. Made a few 2-3 gear pulls, which I did log and throw on Datazap. Car ran great as it always does when warmed up.

VERY INTERESTINGLY I got a code 2c2d o2 sensor before converter coasting mode check. Never have I seen that one before, erased it and tried to make it come back accelerate hard, coast for a while and it didn't come back but I did notice in the logs on decel there is a pretty big variance between the o2 sensors. Bank 2 is 'leaner' than bank 1. Keep in mind bank 1 might be 24-60:1 but bank 2 is consistently 10-20-30-50 points leaner???

[BSM n54iS]

Originally Posted by turbo6justin

After the frustration of the afternoon, I took it out to get gas and hoon around a bit. Made a few 2-3 gear pulls, which I did log and throw on Datazap. Car ran great as it always does when warmed up.

VERY INTERESTINGLY I got a code 2c2d o2 sensor before converter coasting mode check. Never have I seen that one before, erased it and tried to make it come back accelerate hard, coast for a while and it didn't come back but I did notice in the logs on decel there is a pretty big variance between the o2 sensors. Bank 2 is 'leaner' than bank 1. Keep in mind bank 1 might be 24-60:1 but bank 2 is consistently 10-20-30-50 points leaner???

These are original O2's with 133k? You need to replace them regardless at that point, and then ya that might also be your issue too. They're generally good for only 100k or so, at least need to get pre-cat o2's if you don't wanna do the rears