E36 328i - Intermittent rev drop / power loss

[BGarside]

Hi all. Hoping for some advice from the E36 heads on here.

I have an intermittent fault where the revs die while driving my car. This usually only occurs for a split second, such that the engine doesn't actually stall but the car just bucks violently as the engine revs just die away, but on one occasion the engine totally cut out (while overtaking on the motorway!) and I had to restart.

I've had this problem while accelerating, once while sitting in traffic at idle and at a steady speed on the motorway. The fault has been fairly infrequent, maybe happening once in every day of driving. Seems to be unrelated to engine revs, load, speed etc.

Cam sensor was replaced 2 years ago when the engine started stalling when out of gear, but other electrical bits are original.

What could cause the engine to die like this? I guess a dodgy MAF would affect idle but I believe the engine can still run without it. Could it be a failing crank sensor. Which other parts could cause a complete loss of power/revs? ECU? Coil packs (but surely not all would fail together?). Fuel pump?

Thanks in advance.

Ben

[helix402]

The wiring on the fuel pump itself, or on the connector can break sometimes. This could cause your fault.

[E-bmw]

Was the cam sensor a BMW one?

The pattern ones don't last.

Have you checked the air intake convoluted rubber boot for cracks.

MAF could be a good call, again, don't use cheapo ones, get a good second hand if the OE ones are too expensive.

[BGarside]

Cam sensor was genuine BM. My local indy suggested no point using aftermarket.

Rubber intake hose is fine.

Is the fuel pump wiring issue something I could see?

Can't understand why fault is so infrequent, I guess more difficult to diagnose but don't want the engine dying on me while overtaking or leaving me stranded somewhere....

[helix402]

Yes, fuel pump wiring can be checked by eye. Remove rear seat base. Check connections to pump under metal panel. (Can’t remember which side is the pump-it’s the one with more wires going to it, the other is just a sender. If this connection is ok, you need to remove the pump to check the wiring is secure to the pump itself.

[BGarside]

Thanks. Sounds like I'll need to take a look at both sets of wiring then.

Dumb question I guess but how does one remove the rear seat base??

[Funk]

This may help: https://www.pistonheads.com/gassing/topic.asp?h=0&...

I'd go with the camshaft position sensor though, my E46 330Ci kept stalling intermittently and it was that which solved it in the end: https://www.youtube.com/watch?v=AvZKbr5T92Y

Edited by Funk on Monday 4th June 12:45

[helix402]

BGarside said:

Thanks. Sounds like I'll need to take a look at both sets of wiring then.

Dumb question I guess but how does one remove the rear seat base??

Seat base just pulls up (maybe forward too) and out.

[4rephill]

helix402 said:

BGarside said:

Thanks. Sounds like I'll need to take a look at both sets of wiring then.

Dumb question I guess but how does one remove the rear seat base??

Seat base just pulls up (maybe forward too) and out.

The seat base is just held down by a couple of large spring clips - It needs a reasonably firm pull, but it will just lift up.

[BGarside]

Thanks. Will take a look at the weekend.

[BGarside]

Funk said:

This may help: https://www.pistonheads.com/gassing/topic.asp?h=0&...

I'd go with the camshaft position sensor though, my E46 330Ci kept stalling intermittently and it was that which solved it in the end: https://www.youtube.com/watch?v=AvZKbr5T92Y

Edited by Funk on Monday 4th June 12:45

Cam sensor was replaced last year as mentioned above. Only really affected idle though, didn't cause sudden total power loss while driving.

Would failing crank sensor give symptoms like I'm having?

[E-bmw]

BGarside said:

Cam sensor was replaced last year as mentioned above. Only really affected idle though, didn't cause sudden total power loss while driving.

Would failing crank sensor give symptoms like I'm having?

Don't know but MAF certainly will, a bad connector on mine was like hitting a brick wall a few years ago.

[Funk]

BGarside said:

Funk said:

This may help: https://www.pistonheads.com/gassing/topic.asp?h=0&...

I'd go with the camshaft position sensor though, my E46 330Ci kept stalling intermittently and it was that which solved it in the end: https://www.youtube.com/watch?v=AvZKbr5T92Y

Edited by Funk on Monday 4th June 12:45

Cam sensor was replaced last year as mentioned above. Only really affected idle though, didn't cause sudden total power loss while driving.

Would failing crank sensor give symptoms like I'm having?

Crank sensor was next on the list if the cam sensor didn't solve the stalling...

[BGarside]

The issue continues.

Car was idling on the drive when revs dropped almost to stall, then recovered, all in a second or two. Disconnecting MAF plug engine still ran fine, revs rose slightly when connected. Seems MAF is ok. Didn't have time to check fuel pump wiring as was too busy changing the oil so I guess that's the next thing. Fault occurred again on Sunday while accelerating, car bucked violently due to sudden power loss.

Annoyingly difficult fault to diagnose and don't want car dying on me when I'm in Yorkshire at the weekend!

[Funk]

I know you said you replaced it last year but it all points to cam sensor I reckon.

PS. I have a load of spares for my old E36 328i which you are welcome to for the cost of the postage if you'd like? I've pinged you an email with a list of the bits I have.

Edited by Funk on Tuesday 12th June 01:17

[BGarside]

Thanks for the offer! Replied.

Symptoms are a bit different from when the original cam sensor failed last year. Then, the car pulled jerkily and was lacking power after a cold start and when changing gear it would not idle at a stable speed and tended to stall. The idle speed also bounced up and down when the car was idling at a stop.

This time the engine runs perfectly from cold, idles fine between gearchanges and the idle speed is stable, but the revs tend to drop right off at random, infrequent intervals, maybe once each time I drive the car, for literally about a second then recover. This doesn't just happen at idle but also when accelerating in gear.

The replacement cam sensor was genuine BMW as my indy advised aftermarket ones were crap.

Still got to check the fuel pump wiring but what happens when a crank sensor dies??

[E-bmw]

E-bmw said:

BGarside said:

Cam sensor was replaced last year as mentioned above. Only really affected idle though, didn't cause sudden total power loss while driving.

Would failing crank sensor give symptoms like I'm having?

Don't know but MAF certainly will, a bad connector on mine was like hitting a brick wall a few years ago.

As I said above mine did exactly what you are describing totally intermittently.

Disconnect the MAF & leave it disconnected & see how you get on.

It will run fine without it, all it does is fine mixture adjustments when on throttle, you may get a slight hesitation & that is about all you will feel but you need to eave it disconnected while allowing time for any issue to still show itself or not as the case may be.

[Dave0321]

You really need to get it plugged in as it could be a couple of sensors...

But symptoms are similar to when my crank sensor was dying on my old 328i.

[BGarside]

OK thanks. Will try driving with MAF disconnected. Would this damage the catalysts as I might need to drive like this for some distance to be sure the fault does not manifest?

Maybe I'll consider getting my indy to fit a new BMW crank sensor if that does not work.

Anyway, this gives me a way ahead so thanks for the feedback!

[dmarkovina]

It does look like crankshaft sensor. Inpa readout should confirm that. I had no issues with Febi sensors - it seems they are repackaging VDO sensors - OEM.