another "cuts off under load"

[e30rapidic]

not the spark cutting out....but like the engine cuts off from fuel loss.

Some of you may know that I just built up an s50 and threw it in my cabrio. Idles smooth as silk and rode great under a break in ride, I thought all was well......until the first time I gave it some welly as the Brits say. The engine cuts off completely anywhere between 2500 and 4000 rpm's under hard acceleration.

The VSS is hooked up from the green plug on the cluster directly to pin 42 on the DME.

I have no codes according to the Peake Tool. It did throw an IAT code when I first hooked it up (the IAT sender had not "clicked" into place) so I know it works.

All gauges and idiot lights work.

After the engine cuts off, it takes a few seconds of cranking to get it run again. Even longer if I just leave the the car in gear in hopes of the engine firing back up. It burbles and stumbles for a few seconds after firing back up and has no power at all. It's got a new fuel filter, new plugs, cleaned injectors, coils are good, VANOS rebuilt and cam's timed while on the engine stand. 3.5 AFM, Headers, TRM tune.

I may try to put the original S50 chip in but I seriously doubt its the chip. The fuel filter is brand new but as I'm typing this....I'm wondering if the fuel pump is not flowing enough?!?! as in failing?!

outside of the fuel pump....any other suggestions? I think i've covered all bases that came up from searches. No codes, no loose wires or similar. Even the reverse lights work..haha

Cheers

[e30rapidic]

guys with the early style harness with a c104 3 pin plug in the glove box area...

Can I hook up pin 42 from the e36 ecu directly to one of these? would it be the bk/bl wire?

[e30rapidic]

guess I like bumping my own threads.

Disconnected the VANOS connector - it pulls without issue up to 6k. Slowly but surely figuring this thing out....

[ck_taft325is]

Clearances when the VANOS engages if you're not spot on TDC can cause this issue but as Graphik's S50 is having the same issues I'm curious as well.

[graphikg]

WOW!!! I cant believe you are having the same problem as me. Interestingly enough, I also have a TRM tune for an S50 with euro MAF- but mine is 3.2L and has s50 cams. We should really put our heads together on this. I rebuilt my head with new lifters and valves, yet nothing has been resolved. I also tested the car with 2 different rebuilt Vanos units and still nothing. I religiously get shut down at around 3k with Vanos plugged in, BUT with the vanos unplugged I am sure I will walk on my e36 M3!

My next moves are changing out my cam sensor, since changing my crank sensor didnt do anything. And if that doesnt work; then I am replacing the entire harness to an e36 harness (mine is M50 e34 harness now).

Questions for you: When did you start having these symptoms? Is there a wierd noise at the time your engine shuts off?

Edit: Oh, just to let you know; mine started happening after an overrev yet still continues on a fully rebuilt head, and MAF, Vanos advancement, timing, scoping of crank and cam sensors, and fuel pressure all check out ok. Also no codes from peake scanner.

[Jason89i]

this was discussed over here.... http://www.r3vlimited.com/board/showthread.php?t=195370

had the same issue with a fresh s50. it was cam timing. intake (installed with blocks) was too far advanced. We re-timed it about 5 times and tried various vanos units. It was only after taking it to a bmw race mechanic that we were enlightened. he "dialed" in the cams, car pulls like a freight train. exhaust was off by ~2deg and intake by ~7deg. word to the wise..... installing cams "straight up" does not always work.

cheers, jason

[graphikg]

Jason... did you have a weird mechanical sound coming from the motor when your car shut off (while vanos connected)? And were your cams factory or aftermarket?

This just might be our issue rapidic! Any write-up on how to "dial" cams?

[e30rapidic]

cool, thanks for the response. I'm going to pull the valve cover tonight and see what the timing blocks look like. I timed it all on the stand but it could well be off after all. I'll re-time/check it with the VANOS tools and then check with a dial indicator to compare.

Graphikg, I have seen a write up on here how to dial them in, believe its how the M50 guys with the exhaust swap have to set them up. I'll search a bit tonight, supposed to be studying right now!!! Will keep you posted.....

Had a thought that it might help to have a buddy run the car and shut it off while you have your head over the motor trying to diagnose the sound or pinpoint where it's coming from if you haven't already. If it is in fact coming from the VANOS unit, I wonder if the metal plunger is scraping against the housing?? Are your spring plates in the right order?

[graphikg]

Ya, post up the write up about the dial indicator if you find it - but DO YOUR HOMEWORK FIRST! HAHA.

I thought about having a friend ride a bike or something next to the car to try to hear the sound when it shuts off, but you cant have someones head over the motor to hear the car since it has to be under load and moving. Do you have a weird sound though when the car stalls off?

[Jason89i]

Ya, post up the write up about the dial indicator if you find it - but DO YOUR HOMEWORK FIRST! HAHA.

I thought about having a friend ride a bike or something next to the car to try to hear the sound when it shuts off, but you cant have someones head over the motor to hear the car since it has to be under load and moving. Do you have a weird sound though when the car stalls off?

vanos does not engage unless the dme sees the car is in motion. hence, you're not having the fault unless the car is in motion.

just take it to a good bmw engine builder..... someone qualified to set the cams WITHOUT the blocks.... and be done with it. I think we spent less than 600 at the dealer (have a fanatical bmw engine guru with his own "race" garage.)

just to recap other threads. we had the same issue 4 +/- years ago when i had an s52 and my buddy had an s50. We installed schrick cams ("square up" with timing blocks) on a fresh s50. exact same problems. spend 4 nights trying to diagnose. we came to the conclusion that the intake cam timing was off. took it to Al, he dialed them in with a tdc finder and a degree wheel. exhaust was off by +/- 2 deg, intake off by +/- 7 degrees. now, the car RIPS. Ask around, it is a common problem with schricks being installed "square up."

i took my s52 to Al for a spun crank hub. he again dialed in my STOCK cams at the same time. They too were not set for optimal track cars. I think he moved them +/- 3 degrees and the car NEVER felt as good.

this topic is getting BEAT TO DEATH. just take it in to the best local bmw race car builder and be DONE with it.

cheers, Jason

[e30rapidic]

fixed it - the VANOS timing was off. Re timed and all is well!

this video was helpful

http://www.youtube.com/watch?v=6khny0mbHeI