1997 850 t5 MAF idle woes p0103

caseyblu · Post by **caseyblu** » 19 Sep 2017, 22:01

My 97 850 threw a p0103 code, and started stalling at idle:

A mechanic in the town I live in replaced the MAF with a cardone remanufactured bosch MAF, when I picked it up the car ran much worse.

When I got it home, I tested for vacuum leaks (something the mechanic didn't do), fixed/replaced a bunch of decaying/broken vacuum lines/elbows, and got the car running basically like normal, deleted the code, and it came right back. Twice now.

Per this message board and others I have:

-checked thoroughly for vacuum leaks (visually, w/ carb cleaner, and smoke test) and repaired where necessary (possible there's more, I'm new at this, but I've spent a fair amount of time looking for leaks).
-reset the ECU by unplugging the battery for ~30 mins (pressed on brake pedal periodically to make sure it drained)
-Tried driving the car w/ the MAF unplugged, ran much worse, stalled immediately when I put it in gear unless I gave it gas
-tested the wiring to the MAF, and tested voltage at the MAF. Grounds to pin 1 and 2 are good, 12 volts at pin 3, signal level at idle was correct when back probing pins 2-4.

Car still stalls and dies occasionally at idle after warmed up (~5 mins), and sometimes stumbles/runs rough on deceleration. Problem is much worse with the a/c on.

More Clues: I drove the car around for a while today and monitored MAF g/s - at idle it's around 5 g/s and seems to increase in proportion with throttle increase, however when the car stalls/stumbles it will often spike to as high as 250 g/s.

Short term fuel trim goes as low as -6, but usually stays positive, low single digits
Long term fuel trim is around 3.1

I'm thinking more thorough testing of the wiring to the ecu and perhaps ordering a new oem bosch MAF.

Any insight appreciated!

Post by **erikv11** » 19 Sep 2017, 23:57

Many, many people have had trouble with the Cardone MAFs, I would have said 95% chance that is the problem, even before you looked into other obvious explanations. It may say Bosch on the housing, but the electronics are from somewhere else now that it is rebuilt.

Can you get your hands on a junkyard Bosch MAF, for testing purposes? Much cheaper than shelling out for a new one, and that is definitely what I would try next. Any 95-98 has the same MAF, turbo or non-turbo. Essentially every one at the junkyard is working.

caseyblu · Post by **caseyblu** » 20 Sep 2017, 08:32

ok, good to know, I sort of had a feeling, came across tons of threads recommending only using bosch oem.
Also, my wife just reminded me that the car wasn't dying before they put the cardone MAF in, so...

I'm just gonna order the Bosch oem MAF, I'll report back when I get it installed.

Thanks!!

caseyblu · Post by **caseyblu** » 21 Sep 2017, 15:16

Got the MAF, pulled the intake hose while the car was still warm and there was white smoke coming up from the intake -- pcv?
Thinking I should leave the old MAF in the car until I can replace the pcv system, as maybe that's what caused my CEL in the first place and the oil smoke can't be good for the MAF, right?

Anyways, won't be able to do this for a couple weeks...

caseyblu · Post by **caseyblu** » 10 Oct 2017, 20:36

If anyone's keeping tabs:

Just got finished replacing the pcv system, which was badly clogged, and put the new MAF in -- so far so good. Idles smooth and no stalling w/ full A/C. Didn't have time for a thorough test drive.

One question, if anyone's still checking this. The intake manifold was missing a bolt, and didn't have a support bracket.
I'm ordering a bolt tomorrow, but was wondering: how important is the support bracket? I couldn't find a replacement by googling...

Post by **erikv11** » 10 Oct 2017, 22:33

Good work on the PCV. Got the drain tube clean into the oil pan I hope?

A missing IM bolt could cause trouble for sure - resulting vacuum leak and unmetered air. If by the support bracket you mean the one on the lower right IM bolt, that guides the PCV pipe? Not important at all, up to you.

I'll happily send you IM bolt(s) for free from the parts car out in the back, but you have to wait for snail mail to do the job. Could even grab the bracket if you really want it, let me know.

Post by **abscate** » 11 Oct 2017, 04:41

Well done Casey. It was smart to take care of that PCV

caseyblu · Post by **caseyblu** » 12 Oct 2017, 17:28

New Bosch OEM MAF officially fixed the problem. Couple days now, some long drives and it's running better than ever. No CEL.

thank you abscate and erikv11 . Pretty excited I got through all that on my car. Couldn't have done it without this site!

erikv11: thanks for the offer (!) but I've already got some on the way. And I'll skip the bracket if it's not important.

Post by **precopster** » 14 Oct 2017, 16:42

I'll bet if you look at a live MAF reading now it's more than double the 5g/s. PCV can affect metered air levels slightly so I wonder if this would have been the solution for P0103 from the beginning.