Issue with 97 e39/m52: engine power loss

[brewsterE30M3]

Had to have e39 flat-bedded home on Sat nite (5/14/11)
Started running rough after 60 miles of the 90 mile trip, then stalled and could not re-start. Battery is strong and turns starter OK.
Fuel tank at 1/4 full.
Had new OE fuel pump and fuel filter installed back in Dec/2010.
CEL lit up.

Next day tried starting.....started right up and ran fine....no roughness/missing.
Check faults with Peake reader....3 faults..misfires on #1,#3,#4 cyl.
Cleared faults......drove to gas station filled up w/ premium and drove 10 miles home......car ran fine.....no CEL's
Drove 15 miles to work today...no issues.

Details on e39:
auto
135k miles
K&N air filter with 10k miles

Could the crank sensor be the problem? MAF??

Any help or suggestions are greatly appreciated.
Thanks,
Bruce D.

[victory1auto]

Crank sensor is I think a likely culprit. Moreso than MAF, which usually does not cause no start. [Motor should start even without it plugged in.]

Given you now have no symptoms to diagnose, I would check fuel pressure and volume, charging system DC and AC voltages, and throw a DME relay and a fuel-pump relay at it.

Vic

[brewsterE30M3]

Vic,

Thanks for the comments, I'll start with the CPS.
Rich K. also suggested the CPS....fine minds think alike I guess.
Tho it has not shown the same problems after being driven 80 miles since being towed home.......

Thanks,
Bruce D.

[MrMCoupe]

Bruce,

How old is the battery? I've had similar issues only to find out a battery (which tested good) wasn't.

Mark

[brewsterE30M3]

Hi Mark,
the battery is about 4 yo, however it does turn the starter easily w/o signs of weakness. When it would not start the starter still operated fine.
I'll keep all posted once we figure this out.
Thanks,
Bruce

[victory1auto]

Good point re battery, although not as likely to cause running problems. There have been many BMWs, and presumably other makes, that seemed to crank vigorously yet would not start. The problem was low system voltage during cranking due to a bad battery or high resistance in the circuit.

A bad battery can also contribute towards high AC voltage from the charging system, hence my earlier suggestion.

Vic

[brewsterE30M3]

Well, the old girl stalled out again!

We drove it daily for 2 weeks (about 350 miles) without a problem.
Then driving home from S Jersey yesterday it died, and couldnt restart till it was flat bedded to my drive at which time it started up, like normal!

Conditions before stalling, car was driven for approx 1.5 hours at about 60MPH and had 1/4 tank remaining.

Same symptoms as before: power loss and inability to restart until cooled down. btw.....Engine runs at normal temp. according to the gauge

Filled it up today with Plus and drove 25 miles in 91F heat.....no stall issues.

no CEL with this failure....tho threw 3 fault codes last time it stalled. (???)

Any more ideas guys and gals?????

TIA,
Bruce D.

[brewsterE30M3]

Hi Vic et al,

Well we drove many miles of several 2 + hour trips and have not had any stalling issues since changing the CPS. I noticed that the previous owner had the CPS replaced during a recall (had sticker under hood) when the car had 85k miles....so it lasted only 50k miles!...
Thanks again Dr.Vic for a right-on diagnosis....we are very fortunate to have you as a expert resource.

Best Regards,
Bruce D.

[brewsterE30M3]

Vic et al,

FYI-- I expected to receive a Bosch (or OEM) Crank Position Sensor when I ordered it from BAV Auto........what I got was a "Delphi" CPS.
Also, they charged me $95 for this non-OEM part, compared to the $70 from e-Europarts for a Febi part.

Any experience with the "Delphi" parts/CPS....????

I have heard that BAV Auto has been doing this "switcheroo" with parts suppliers and not stating the info/details for the supplier.

Best Regards
Bruce D.