m60b40 missing, low idle, back firing

[toffa182]

I'll share an experience of my own.

Short version: A TPS can be bad even if a continuity test is successful.

Longer version: I changed my intake gaskets and after finishing the job the gearbox behaved strangely. While changing the gaskets I also cleaned the manifold and attached parts.

I hooked up my computer and I could read fault codes from the gearbox, codes indicating the gearbox was not receiving proper throttle position values. So I grabbed my multi-meter and started measuring.

The TPS measured fine, but when looking at live data in INPA the throttle position was reading full all the time, except at about 3/4 throttle where it was showing 23%! I quickly switched the TPS connector over to the ASC+T pot and I immediately saw healthy values. Perhaps the pot got some water in it as I was cleaning the throttle housing.

So I installed another (used) TPS and the problem is gone!

[JGood]

Thanks for that info, good to know. It very well could be the TPS. But I have two, and there is zero change in the symptoms between the two. So I think it's unlikely. I may try another anyway.

[dirtysix]

You say it runs fine, not counting slight stumble, without O2 sensors. Does unplugging the MAF have the same effect? Usually when you unplug these type of sensors the DME reverts to baseline numbers/safe tune. Sounds like, for some reason, it's drowning itself when taking input from all sensors. I wonder if the DME knows the engine is up to operating temp/might be running startup mixture? Away to check the DME's receiving engine temp signal?

Also, the stumbling may just be the result of running a light fly. With a dual mass or auto it would be masked. Even in the 2001 540 I have, if you raise the revs with the car in neutral, standing still, with no load it stumbles/shakes at about 2500 rpm. An odd thong that is completely masked by the trans and, I would think, the horrible massive dual mass thing BMW insists on using, whilst driving.


Just a thought.

[JGood]

It's been a while, my issues sill exist. Replaced everything multiple times. Since the last post I've tried another MAF and TPS. No change.

Summary: With o2's unplugged, the car has a bad hesitation every time I get on the gas AFTER coasting/engine braking. It lets out a loud backfire and stutters for a second, then after a second just straightens out and pulls fine. So if I'm cruising around, leave off the gas, and then get back on the gas, it will backfire and hesitate before accelerating.

If I plug in the o2 sensors, it does the above, in addition to stalling if I leave off the gas below 1500 RPM's. This is difficult to explain, but basically I can rev it from 1500-6500, leave off, and everything is fine. If I rev it to 1200 and leave off, the RPM's fall to idle and just keep falling and it shuts off. This also applies to driving around: if I'm at 1000 RPM's and push in the clutch, it stalls. Push in the clutch above 1500, it returns to idle. So basically, maneuvering around parking lots, it stalls every few seconds unless I rev it to 1500 before leaving off the gas.



I decided to get the car back on the scanner. Before doing so, I went back to my spare DME with the factory chip. Oddly enough, the car does not stall as easily with that chip, and the missing/backfiring/hesitation while driving is definitely less severe (but it's still there).

So, I hook the car up to the scanner with the factory chip, and the o2 sensors connected. The o2 voltages fluctuated as expected, so the DME is getting a signal from them. BUT, I had no fuel trims, at all. No change in idle or part throttle trims. So the DME was not using the o2 signals to do anything.

So I swapped DME's, back to the aftermarket chip I bought. This time, I had idle fuel trims, but no part throttle trims. And this is with the chip that the car runs worse with.

So, what could possibly cause this? Is the DME not going into closed loop mode?

Every part/sensor that helps tell the DME when to go into closed loop mode has been replaced... some of them 2 or 3 times. MAF, TPS, temp sensor, IAC, IAT, o2's, etc. in addition to everything else: CPS, injectors, FPR, filter, pump, spark plugs, plug boots, coil packs, CCV, all intake gaskets, etc... have all been replaced. The only thing I haven't replaced yet is the cam position sensor. It tests good and should only control batch firing for the DME, not actual timing advancing/retarding, which should have zero impact on how the engine runs.

[mark///m3]

Can you get your hands on another factory dme? Sounds unlikely but maybe you have two bad ones. Also when you switch out your parts like the airflow meter.... Which ecu are you using? I'd try switching with the factory one. The fuel trim reading should be a result of the maf and o2 data so its weird with one ecu you have it and with one you don't.

[_JohnnyD_]

Did you ever figure this out? My car is doing something simular. I think I have some leaks in the manifolds which I'll fix on the weekend but that didn't end you being your problem.

[JGood]

Nope, still battling it. I think my issue is going to be something crazy, like interference in the wiring harness or something.

My symptoms are down to:

Jerky-ness, some unusual crackling from the exhaust, and a slight hesitation, all of which occur only when getting on the throttle after engine braking. It feels EXACTLY like a bad throttle position sensor. But, I've tried 5 TPS's, 2 throttle bodies, have verified proper resistances of the TPS's, continuity of the wires to the DME connector, and have verified on a scanner that the TPS voltage readings are properly correlated to throttle inputs.

And it usually stalls if I leave off the gas below 1500 RPM's while engine braking.

I'm going to get a fuel pressure tester and do some fuel pressure monitoring while driving so I can see what the pressure is doing as it's hesitating as I get on the gas. I know it goes from 51 psi to 47 psi as it's stalling when I leave off below 1500 RPM's. But, I have a new pump, filter, hoses, FPR, injectors, and rail. So nothing is wrong with the fuel system.

Had it on a Snap-On Ethos scanner for 4 hours while driving around a few weeks ago, all readings seemed fine and within appropriate ranges. All sensors were responding and seemed to be outputting proper readings.

[RobertK]

I'm starting to wonder if there is an issue with the wire harness somewhere. My last swap had a bad coil ground that was frayed at the DME and I almost blew my brains out trying to track down what was causing my issue.

Have you found someone with a GT1 setup yet?

[JGood]

I'm starting to wonder if there is an issue with the wire harness somewhere. My last swap had a bad coil ground that was frayed at the DME and I almost blew my brains out trying to track down what was causing my issue.

Have you found someone with a GT1 setup yet?

No I haven't.

It almost has to be a harness issue, or an engine issue (timing?). I've replaced every single sensor on the engine, most of them 2, 3, 4 times. And I've tested all of them per Bentley specs. The Snap-On scanner showed everything functioning properly.

I'll probably try to find another harness and throw it on. Even though I've tested it end to end and haven't found any issues...

[Jonsku]

What about mechanical problems - timing and compression test for cylinders? Spark plugs and coils?

[JGood]

What about mechanical problems - timing and compression test for cylinders? Spark plugs and coils?

Well, I mentioned timing as a possibility. But I bought the engine from a running 740i, and never touched the internals.

Already compression tested the engine, and replaced coils, boots, and plugs.

[FLG]

Justin your more then welcome to use borrow my fuel pressure tester.

Gonna be reading thru this thread and see if I could maybe come up with something

Sent from my Galaxy Nexus using Tapatalk 2

[Jonsku]

Well, I mentioned timing as a possibility. But I bought the engine from a running 740i, and never touched the internals.

Did you change the main chain tensioner?

[JGood]

Did you change the main chain tensioner?

Nope. The engine is dead quiet so I figured there's no reason to.

[JGood]

Justin your more then welcome to use borrow my fuel pressure tester.

Gonna be reading thru this thread and see if I could maybe come up with something

Sent from my Galaxy Nexus using Tapatalk 2

Thanks for the offer, but they're only $20 at Harbor Freight, I'll pick one up tomorrow.