Edit, putting on hold for now. Despite shop being adamant to not smoketest the car and my adaption looked good, INPA begs to differ and shows a pretty bad vac leak. Going to deal with that first and report back.

Airmass idle: 11 kg/h (3.06 g/s)
Lambda Integrator banks 1, 2: 12.4%, 14.5% (went to 0% when rev'd)
Lambda Adaption multiplicative banks 1, 2: 7.7%, 7%
Fuel Pressure: 453 kPa (65.7 PSI)
Lambda Regelfaktor (idk which this is): 12.2 / 15.1

 

A shop adamant about not smoke testing is a shop that doesn't smoke test, I wouldn't ignore your gut feeling. There's ways of doing your own cheap smoke test. Fancier cigars give bonus points.

I'd double check that all your work is concise, especially where it seems you've done alot to the vehicle and I know how easy it is to forget something. Could be a loose vacuum hose somewhere on the intake. MAF are expensive to replace and not easy to diagnose. I'd be tackling the cheap jobs first before coming around to the replacement of the maf.

Check the link in my signature, it's got loads of useful information on what/how to log the data that will be most helpful to us. As well as Guides to common problems with rough idles, starts and fuel trims.

 

A shop adamant about not smoke testing is a shop that doesn't smoke test, I wouldn't ignore your gut feeling.

Its a BMW race shop that builds Spec36 & 46 cars. I feel like this is a case of "ur issue isn't worth our time" brushoff.

Will read over everything u and Bali linked. If anything, I'll remove everything to the manifold. Kinda hoping the main gasket sealed fine on the manifold (since the manifold is the biggest tedium to remove....fuel rail etc etc) and that its something accessible. I guess it could be one of the 2 hoses on the back of the manifold (Brake booster or evap purge)

 

• Fuel trims, lean codes, misfires, and how to diagnose

 

I would double check the fuel pressure with a gauge.

The 65 psi is about 30% higher than the M54 fuel pressure spec of 50psi +- ~3 psi

 

BMW doesn't measure fuel pressure, so that number has to be calculated from other values...

Are you getting any shadow codes from cam or crank sensors?
I've had an intermittent cam sensor give this exact problem...

hth

t

 

Hey all,

Took a break from this to try and track down some of the problems discussed above and fix other issues to limit potential causes. Found some vac leaks I missed in some boots and also replaced the booster which was leaking. The only remaining leak is a known leak in the DISA valve o ring. Tried replacing, but being non OEM the fitment isn't great. Currently acquiring a replacement.

That said, I'm still getting these troubled starts occasionally. To clarify, these bad starts ARE NOT every time. Its random, hot (even track hot) or cold engine. Back to back starts or sitting for awhile....
Usually looks like: Long cranking (1-2s)-> starts but partial firing on some cylinders -> blip throttle and then its fine (notable fuel smell whenever this happens from the front of the car, not the exhaust as far as I can tell).

Went ahead and summarized everything I've done and tested wrt 4 needs for starts:

1) Air - smoke tested, there is a leak at the DISA valve (shocker) and will be resolving, but thats it, everything else is now clean (boots, booster, gaskets, ccv all replaced). Maf has been swapped with another spare someone gave me (both COULD be bad but behavior is similar before and after), ICV & TB recently cleaned

2) Fuel - Fuel pump is 2 years old (VDO), fuel filter + reg is 1 year old. Injectors were removed, cleaned and tested when all the air box was removed. I have NOT tested pressure on the fuel rail yet.

3) Compression - no leakdown test, but compression test just gave me back 175-180psi on all 6 cylinders. There is some oil seeping into the plug area from the internal VCG, but not too much. Definitely going to redo. Most notable on 5+6

4) Spark - new spark plugs (NGK) and I just put in new Eldor coils hoping it would resolve the issue. No change. Alternator voltage is fine, battery voltage also fine.

At this point, I'm kinda lost beyond retesting everything? Assuming everything above is as tested, my only remaining thought are the cam/crank position sensors? Any other thoughts on values to check in INPA/ISTA or items to test/replace?

 

I have NOT tested pressure on the fuel rail yet.

Long cranking (1-2s)-> starts but partial firing on some cylinders -> blip throttle and then its fine (notable fuel smell whenever this happens from the front of the car, not the exhaust as far as I can tell).

Fuel - Fuel pump is 2 years old

Back to back starts or sitting for awhile....

Looks like you've got all the pieces to the puzzle, just gotta figure out how it all goes together.

MAF seems to be under reporting, a user by the name of @NZ00Z3 has done a lot of work with diagnosis with MAF failures. He'll ask for some logs, cold start, hot drive, rev rise. Details on these can be found Here

I'd be testing the fuel pressure. It should be ~50 psi on key on. Anything below that is signs of a failing pump.

Fuel smell, leaking lines either near the fuel rail or fuel filter. Look for rubber lines, dry rotting especially around the fuel filter and the return hose near the intake.

Good luck!

 

Fuel smell, leaking lines either near the fuel rail or fuel filter. Look for rubber lines, dry rotting especially around the fuel filter and the return hose near the intake.

Yea, I plan to double check. The smell I believe is just from injectors firing and no boom booms happening...
Its possible the injector test just missed that one of them was hyper leaky.... Can likely prime the pump and see if there's a fuel smell in the intake manifold.
Fuel pressure test will confirm. There's no smell if I get a normal start.

Will read over the linked data re: MAF. I haven't looked at the MAF numbers after I swapped units, but again both could be bad. It was a spare a track friend had.

 

The numbers on your first post where my reference point for MAF numbers. Your average 3.0 maf should be anywhere from 3.5-4.5g/s at 700 rpm.

 

Are you getting shadow codes for cam or crank sensors?

I have a semi- proven suspicion that they can soft or slow- speed fail, and will confuse the DME on
startup. Once the engine's running, it seems to accept valid data from them, but at least
on my car, it leaves a shadow code for exhaust cam sensor.

The other test is fuel pressure after resting. A slightly- leaking injector will flood that cylinder,
and that leads to long cranking and rough running until the cylinder clears. The test for that is
that the rail holds pressure pretty much indefinitely .

whuts I gots.

t

 

Are you getting shadow codes for cam or crank sensors?

I have a semi- proven suspicion that they can soft or slow- speed fail, and will confuse the DME on
startup. Once the engine's running, it seems to accept valid data from them, but at least
on my car, it leaves a shadow code for exhaust cam sensor.

AFAIK, not yet. Historically the only shadow codes I was getting was on lean mixture from the vac leaks I chased down. I'll see if anything current is showing up now that many have been resolved. Still the one leak from the DISA o ring, but when I checked, I was pretty low on additive mixture. No codes re: sensors.

The other test is fuel pressure after resting. A slightly- leaking injector will flood that cylinder,
and that leads to long cranking and rough running until the cylinder clears. The test for that is
that the rail holds pressure pretty much indefinitely .

Yep. Atm, injectors were only assumed due to being tested, but its possible they screwed up.
I'll get a fuel pressure tester on there asap. Either order OTC on AMZN or swing to harbor freight and get their knockoff.

Find and fix the fuel leak ASAP, before you get a big boom boom.
Unless the fuel smell is directly from the exhaust pipe, it is a leak and a risk.

Explain how you can have a fuel smell in engine comlartment from injectors firing.

I'll triple check everything again and get a fuel pressure tester on the fuel rail to see if there's a pressure drop.
Given that the smell only occurs on these bad cranks, it was viewed as excess fuel flooding the cylinders and intake manifold.
There's no smell when the engine is running and no smell when the pump primes on ignition 2.

 

yeah, a flooded cylinder will poot raw fuel out the tailpipe, giving a pretty strong smell as the car first starts.

But a misfire from other causes will smell too, but to a lesser extent. The charge in the cylinder didn't fire, so it's expelled out the tailpipe.

All of this goes away quickly, as soon as the cats come up to temperature.

In your shoes, I'd rule out the injectors first. It's really odd that it's intermittent- a leaky injector(s) almost always leaks no matter what...
but given the symptoms, it's just the cost of the pressure tester to make 100% sure they're good.

t
thinking about adapting a pressure sensor to the fuel rail permanently....

 

thinking about adapting a pressure sensor to the fuel rail permanently....

This sounds like a stellar idea, it could be run as a stand alone sensor on a guage. Like a boost guage but mounted to the fuel rail.

 

If you want to check the MAF's, set up OBD Fusion and run a Rev-Rise Log (see Below). Post the log in DataZap or post a link to the log here and I'll run the log through my MAF model and tell you what is going on.

Rev Rise.
This test is for checking your Mass Air Flow Meter (MAF). Hot engine and Cat’s, stationary car. The test is best done just after a drive.

Slowly raise the Rev's of the engine up from idle to 3,000 rpm. I mean slowly. It should take you 3-4 minutes to do this test. It takes some skill to do this test due to the lightly loaded engine. A little throttle change results in a large rev change. Don’t run up and down the rev range getting used to the control. If you stuff up the first part of the test getting used to controlling the small rev changes, then redo the test.