96 E38 728I M52 Hard Starts when warm, Tried multiple fixes, Getting desperate

[GrandClam 1]

Hi All

This issue has been the bane of my driving existence the past year and I just can't seem to get a handle on what is causing it.

A few bits of context that might help.

firstly  the Car ALWAYS starts totally fine when its cold. First thing in the morning I have never had an issue.

secondly The Codes have been read at my mechanic and have noted a cam angle sensor (my mechanic said sometimes this can be a false reading and he was right we will get into that in a bit)

Third about a month or two ago I replaced my battery and this issue went away / was severely reduced for about a month. to the point where i thought id fixed it but then about 3 weeks ago it came back.

4th I have now replaced the cam angle sensor and spent $200 bucks on it and it has solved absolutely nothing.

 

These hard starts range from splutters and stuttering into just plain not turning over.

When the car is running its a dream. there's no loss of power at all and it runs perfectly other than this issue.

Can anyone help me here. all advice and insight would be greatly appreciated

[jom 96]

I had this problem years ago and I think it was the crank sensor, the insulation rots off the wires or something. If you're going to try it - don't go for OEM - Aliex have them for $15 or so.  if you're worried about longevity buy 3, you'll still save heaps of money.

[GrandClam 1]

ah yes the crank sensor was the other thing that showed up on google.

$15 is certainly a lot more reasonable for a sensor than 200.

thanks for the advice i will probably give this a go

I assume by aliex you mean ali express?

Edited September 13, 2022 by GrandClam

[Eagle 1516]

You can the OE VDO crank sensor from Spareto for $133 shipped via DHL. Putting a $15 aliexpress special sounds stupid given you can't trust it and the time\effort involved to swap it.

[jon dee 500]

4 hours ago, GrandClam said:

These hard starts range from splutters and stuttering into just plain not turning over.

To be clear... does this mean (a) that the starter fails to crank the engine at normal cranking speed, or (b) that the starter cranks the engine normally but the engine fails to fire ? 

Just trying to grasp whether it is a starter problem or an ignition/fuel problem.

Cheers...

[jom 96]

3 hours ago, GrandClam said:

ah yes the crank sensor was the other thing that showed up on google.

$15 is certainly a lot more reasonable for a sensor than 200.

thanks for the advice i will probably give this a go

I assume by aliex you mean ali express?

Absolutely. Mine has been working for the past 12 years...

[polley 916]

The output from the Chinese sensors is crap. Standard ecu doesn't seem to mind it much, but a few aftermarket ecus won't have a bar of it.

[GrandClam 1]

3 hours ago, jon dee said:

To be clear... does this mean (a) that the starter fails to crank the engine at normal cranking speed, or (b) that the starter cranks the engine normally but the engine fails to fire ? 

Just trying to grasp whether it is a starter problem or an ignition/fuel problem.

Cheers...

Second one i believe

[jom 96]

17 hours ago, Eagle said:

You can the OE VDO crank sensor from Spareto for $133 shipped via DHL. Putting a $15 aliexpress special sounds stupid given you can't trust it and the time\effort involved to swap it.

mine has lasted 10 years...

[Eagle 1516]

One data point. No reputable business in the trade etc would fit one for reasons above.

[jom 96]

2 hours ago, Eagle said:

One data point. No reputable business in the trade etc would fit one for reasons above.

On the other hand, if you need a working one to test whether yours is faulty, fifteen bucks on a wild goose chase is cheaper than $130. If it was at fault, the Chinese one should last until you buy an OEM one.

(Why does this bring to mind the Python sketch "if you feel bad about eating her you can throw up in the grave???)

[Eagle 1516]

You going to be waiting for the Chinese one to turn up anyway and how long that takes is anyone guess?. Id sooner borrow one or buy a second hand one local if i was going parts cannon route. Personally i dont like doing jobs twice so i wouldn't bother to save a such a small amount and waste my time, each to their own.   

[jom 96]

2 hours ago, Eagle said:

You going to be waiting for the Chinese one to turn up anyway and how long that takes is anyone guess?. Id sooner borrow one or buy a second hand one local if i was going parts cannon route. Personally i dont like doing jobs twice so i wouldn't bother to save a such a small amount and waste my time, each to their own.   

Aliexpress is about two weeks at the moment. If you can borrow one locally, so much the better. We don't all have shedloads of cash...

[Spinner99 53]

I had a look on realoem and it looks like the M52 is a twin cam engine.  is that right?  If so it would have two cam angle sensors, one for the inlet camshaft and one for the exhaust camshaft.  Reading your story it sounds like you've only replaced one, are you sure you replaced the correct one?

[jom 96]

19 minutes ago, Spinner99 said:

I had a look on realoem and it looks like the M52 is a twin cam engine.  is that right?  If so it would have two cam angle sensors, one for the inlet camshaft and one for the exhaust camshaft.  Reading your story it sounds like you've only replaced one, are you sure you replaced the correct one?

As the cams are (hopefully) coupled together. one sensor is enough.

[Spinner99 53]

8 minutes ago, jom said:

As the cams are (hopefully) coupled together. one sensor is enough.

Yeah good point, I should have checked before.  There's only one sensor listed in the parts diagram.  sorry!  https://www.realoem.com/bmw/enUS/showparts?id=GE22-EUR-12-1996-E38-BMW-728i&diagId=11_1480  

[jon dee 500]

So the car starts fine from cold, runs fine when up to temperature until you turn it off. Then it won't start if you stop at the corner dairy and then go to drive away a few minutes later. But if you let it sit for a while (say 20-30 minutes) and cool down, it starts fine ?? 

Kind of unusual that replacing the battery should make the problem go away for a while. Makes me wonder if you don't have a bad connection in the wiring close to the battery or a bad ground. I'd check to see if any of the wires or connections near the battery are hot to touch the next time the car won't start while hot. Leave the battery cover open so you can check before things cool down. 

Cheers... 

[dirtydoogle 383]

On 9/14/2022 at 8:18 PM, Spinner99 said:

I had a look on realoem and it looks like the M52 is a twin cam engine.  is that right?  If so it would have two cam angle sensors, one for the inlet camshaft and one for the exhaust camshaft.  Reading your story it sounds like you've only replaced one, are you sure you replaced the correct one?

M52 up to 98 ran 1 sensor, on the intake cam. 

 

Have the car scanned again, there are 3 different types of cam position sensor that will fit and no consistency between suppliers, and they are not interchangeable 

[Allanw 1051]

Drive it until you think its at a point where it won't start, then check the live data for the cam/crank sensors and see if they are showing plausible signal. Then turn it off and when you try to start it, check the same data. See if it's not there, or not plausible.

Does pressing the throttle any amount make any difference when cranking it?