Author Topic: Engine hesitation. (Read 21072 times)

e9nine · « **Reply #45 on:** August 23, 2007, 08:59:48 PM »

If you're 1000% sure the wire is intact....the pondering continues.

If not...are you still getting the TPS fault code? Does it look like s.one ever got in there to work on the rats nest of hoses? What basically happens is s.one might have forgotten to disconnect it and pulled too hard on it.

I would suggest to check the wiring and not the TPS. With the TPS disconnected, are you getting the same fault code? With the wiring being faulty - plugging or unplugging the TPS makes no difference. Does anyone remember if their car runs with the TPS unplugged? I don't think mine was driveable and able to run right but this was a while ago and my other m42 isn't here to test.

I don't have an m42 immediately near me but I think some of the wires and connectors can be disconnected from the main harness (black box under the manifold or so?). Is this one of those wires?

If not and the wire is inseparable you might have to tap into it and use another connector to bypass the stock connector and plug it into the TPS.

I did this same thing using the female connector that suprisingly slotted right in to the TPS. I can't remember exactly where it came from though as it came from my parts stash :confused: you can rig something though in case you don't have a spare connector to hack up

G.Luck

St�ck · « **Reply #46 on:** August 23, 2007, 09:14:02 PM »

I actually just finished pulling the braces and junk out, and sliding the engine bay side of the harness out from under the manifold.. to on top where I can sort through everything.

No breaks to be seen, no corrosion, no anything. Everything looks choice. I followed it up the big accorian and pulled it back, everything under it looks good.

Removed the wrap on the part of the harness that runs under the cover. Best I can see that bundle is undisturbed and happy.

I pulled back the boots on each BOSCH connector as far as I could, everything looked good. Same for the C101 and the diagnostic connector. Both pulse sensors, and the knock sensor connections at the under manifold wiring box looks great.

The connector at the ECU also looks pretty good. If someone has the PINOUT for the ECU connector ready I'd like to meter out all 3 TPS wires between the TPS connector and the ECU connector.

Oh.. and if the TPS is disconnected with the engine running the CHECK ENGINE light is illuminated steadily.

St�ck · « **Reply #47 on:** August 24, 2007, 07:34:14 PM »

I found all the wiring diagrams and connector pinouts I needed on line this afternoon, and went ahead with testing. All the TPS wires OHM'ed out 0.0 as they should, from the BOSCH TPS connector to the ECU connector. Wiring there is not an issue.

I wonder *if* and this is a big if... if the fault code might actually be legitimate despite the TPS passing the resistance test and visual inspection.

Later tonight, or possibly tomorrow after I reassemble everything I will test the voltages present on the TPS through its range of motion with the engine running... as is the only real important test.

St�ck · « **Reply #48 on:** August 24, 2007, 08:25:14 PM »

OK. All is back together.

With the key on I conducted a voltage test at pin 1 and 2 on the TPS with the connector plugged in (metered with the boot off)

What I found is um.. odd.

BMW spec is:
0.6v @ idle (throttle completely closed)
4.2v @ WOT

My TPS meters out as:

4.36v @ idle
1.08v @ WOT

What the fug? Ha ha... I now understand completely where the code is coming from. Proof positive that a simple resistance test (which it passed perfectly) is NOT a conclusive test.

bmwman91 · « **Reply #49 on:** August 26, 2007, 12:40:31 PM »

Interesting. Either you measured the wrong end of the pot wiper (unlikely since you ave the wiring diagrams), or somehow the pins in the connector ended up backwards. Did the previous owner have any repairs done on it? Weird.

Is the CEL on at all times when driving? The ECU is adaptive to the TPS sensor to accommodate the tolerances in the resistor track, but I doubt it can adapt to a reversed voltage output! You certainly got a mystery vehicle there!

St�ck · « **Reply #50 on:** August 26, 2007, 01:08:31 PM »

Pin numbers and wire colors indicate everything is as it should be, its not a negative voltage problem... which would come with flopped wires, but rather a backwards voltage swing of a slightly different range.

New TPS is on its way, should show up sometime next week.

CEL is never on, but the stop test shows the stored 1216 TPS code. If I start the engine with the TPS disconnected the CEL is on.

bmwman91 · « **Reply #51 on:** August 26, 2007, 07:29:25 PM »

Alrighty, well good luck with the new TPS. Let's hope that is all it was.

St�ck · « **Reply #52 on:** September 02, 2007, 09:10:48 AM »

Finally got around to installing the new TPS.

Nothing has changed

St�ck · « **Reply #53 on:** September 08, 2007, 12:14:15 PM »

After going through everything I can think of I decided it was time to pull the valve cover off and take a peek. The instant I did I could see the timing was off.

The intake cam was nearly dead on, but the exhaust was very advanced. Even backing it off in the slot as much as I could it still wasn't on. I had to pop the sprocket off and rotate it over a tooth to get the adjustment right.

Synced everything up and put it back together. Engine runs MUCH better now, although it is still exhibiting dulated symptoms of what it was doing previously. It is leaps and bounds better though.

bmwman91 · « **Reply #54 on:** September 08, 2007, 12:19:53 PM »

Wow......

How did the timing chain look? Do you know anything about the history of the motor / when or if the timing assembly was ever rebuilt? Usually by 130k miles a complete teardown & rebuild is a good idea, especially if a bad timing chain tensioner piston was ran for a while. I forget...did you pull the lower oil pan and look for junk?

St�ck · « **Reply #55 on:** September 08, 2007, 12:53:42 PM »

I have pulled the lower pan, it was immaculate. I checked and loctited all the bolts...

The timing chain and gears appear to have been replaced, all the rails look good, and the tensioner feels good. I have a feeling the timing was screwed up during that service...

St�ck · « **Reply #56 on:** September 17, 2007, 09:53:51 AM »

Anyone got any more guesses?

nickmpower · « **Reply #57 on:** September 17, 2007, 10:15:41 AM »

switch crank and cam sensors with someone

St�ck · « **Reply #58 on:** September 17, 2007, 10:19:53 AM »

Cam sensor isn't required for the engine to run at all. You can unplug it with the engine running and it won't do anything but make the ECU switch to parallel injection (normally runs semi-sequential)

I'd like to swap crank sensors to run that out but mine is run wrong. Some retard ran it behind the AC compressor so getting it out would require either cutting it, or unbolting the compressor.

bmwman91 · « **Reply #59 on:** September 17, 2007, 12:14:59 PM »

lol

Sounds like whoever worked on the car last was a real idiot. I was unaware that it could even reach that far over. Then again I have not had AC in the car in so long I do not even remember exactly where the bracket sits. IIRC though, to get it running over that far the cable was probably damaged a little.

You said it runs great at idle and part throttle now, and only bad at WOT? If it really does run just fune after re-flooring it, it kinda rules out the cam/crank sensors to me. The cam sensor COULD be causing problems. It does 2 things:
- tells the motronic to use batcked or banked injection
- tell the motronic whether or not to run in true spark-per-cylinder mode or wasted spark mode.

Perhaps the exhaust cam is a little off still (I believe that is the one the sensor reads from) and throws the timing a little?