E36 M52B28 Misfires once warmed up with decreasing rev range

[Bushmechanic 1]

My E36 (NZ New 124k on the clock) is a bit sick. It has developed a misfire once warmed up (heat gauge about half way). when you first start it up she runs great and can rev her to the red line no problem. Then after a bit of driving misfires at about 5500 rpm. Over time it does it at 4500 rpm then 3500 rpm etc etc until its doing it at 2000. You cant drive it after that. it idles fine and starts up no problem. Yet once warm it clearly starves when loaded. The engine does not cut out at all though.

Back ground When I bought the car it had an intermittent missing and cutting out issue. My mechanic suggested I replace the cam and crank sensors as the code it was giving indicated one or both were faulty. I did that and the car ran fine for about a month. Suddenly out of nowhere comes this misfiring issue.

I figured the plugs a probably toasted and all were so I replaced those with NGKs recommended items. Mechanic suggested I replace all coils so I did that too and the air filter. The car has slightly more power but the misfiring is identical to before the new coils and plugs.

I have checked for vacuum leaks and cant see anything worn. All clamps are tight. There is a slight oil leak from the rocker gasket, but that been there since I got the car.

So to sum:

New crank and cam sensors

New coils x 6

New plugs x 6

New airfilter

Can someone help please? could I have a defective cam shaft or crank sensor? Or do I have a vacuum leak and I need to look harder?

Thanks in advance

[_ethrty-Andy_ 2122]

Is the misfire coming up when the DME is scanned or not?

[*Glenn* 854]

Scan it... what are the fault codes ? Exact terms & not "P" codes. It needs to be done with a reputable, reliable scanner and someone with a brain

[Bushmechanic 1]

Not scanned yet. Will be done this weekend. What are the reasons it may behave this way suddenly. Especially given I have changed components?

[e30ftw 395]

Are you using OEM cam and crank sensors?

[Kepes 231]

Revving it to redline while cold probably isn't doing it any favours

[Bushmechanic 1]

Hi guys

yes revving to redline probably isn't helping it, but I don't do it at other times. Just now that I have this issue.

Yes OEM sensors and coils.

I had a chat with a parts guy and he asked me about oil leaks around the rocker gasket, suggesting that a significant enough leak may be causing a vacuum leak? any thoughts while I wait for results from the workshop?

[qube 3568]

i highly doubt rocker cover gasket is causing it.

there is really no point discussing about it or racking your brain for answers without fault codes and a proper diagnosis first.

[Bushmechanic 1]

yup agreed. I have ordered a new VCG as it needs doing anyway. but will wait for the diag results before going further

[SIR E30 68]

Faulty temp sensor springs to mind??

[Bushmechanic 1]

Wouldn't that throw a check light?

[_ethrty-Andy_ 2122]

this thread is useless until scan results come in, and need to make sure historic codes from previous failure have been cleared and not reappearing sending you on wild goose chase. If they have suggested you change all 6 coils, It would be a fair assumption your previous workshop does not have the correct diagnostic equipment, and will not have cleared the errors, which also casts a bit of doubt in my mind if the crank and cam sensors were faulty, however having said that, replacing the cam and crank sensors with brand new OEM ones in a 20 year old car is only ever a good thing.

Edited November 3, 2015 by _Ethrty-Andy_

[BMTHUG 942]

My guess is blown headgasket. Get a cylinder leakage test done

[Bushmechanic 1]

Hi all. I have haf the car checked on a scanner. Gave crank and camshaft sensors. The faults were erased but it throws camshaft sensor again and again. The cam and crank sensors are new so I was very surprised it guves the error. I went ahead and replaced the camshaft sensor and rescanned erased and took for a run. Came back with exact same issue. Misfires exactly the same. Scanner shows cam and crank sensors. Erased then come up with cam sensor only. Very confused!!!!

now I am doubting the new camsensor was the issue at all. Its got a new set of coils and plugs. New sensors and new vcg. What now? Am I missing a vac leak somewhere?

Only does it when temp guage reaches half way.

please help!!

Edited November 28, 2015 by Bushmechanic

[_ethrty-Andy_ 2122]

a cam sensor fault does not necessarily mean its the sensor it self, otherwise why would BMW put it there if its only reason is to fail. The sensor actually does something, the faullt code is just a bread crumb along a path

Edited November 28, 2015 by _Ethrty-Andy_

[Jono51 57]

wow thats roughly 2K in parts alone from BMW, ( MAF, set of coils, plugs and cam / crank sensors

following this with great interest

replacing parts prior to a scan shows a guessing mechanic

Edited November 28, 2015 by JKSE

[Bushmechanic 1]

Ok some one mentioned temperature sensor. I assume this is the engine temperature sensor. I tried disconnecting it and running the car. The only diff was my temp guage didnt work. The car still misfired. I cant understand what the issue is. I have screen shots of all the readings from the scan but dont know how to post here.

The issue arises once the car is warmed up nicely. Temp guage half way. When the car cools down again the issue retreats.

I love this car. Some one please help

[Bushmechanic 1]

Car has been scanned numerous times and varius things disconnected and checked for faults. The problem remains.

Car misfires when temp guage hits half way. But the problem improves if you let the car cool down.

This has to be temp related yes?

Fault codes indicate camshaft. After misfire you see crank shaft sensor join the faults list. But can be cleared. Camshaft sensor fault can only be cleared with engine not running. Soon as you start the car the fault comes back.

Has to be something simple surely

[tawa 150]

Figure out what the cam code actually means, connection fault, read fault, data error, installation error?

Also check your wiring from the crank/cam sensors, could be a dicky connection near something warm...

[hotwire 352]

This thread is a hoot - really. No wonder Glenn hasn't bothered adding to his original post!

This is guessing/throwing parts at its best.

Get the vehicle checked by an educated/ knowledgeable mechanic or sparky

Fault codes on their own mean naff all & as can be seen in this thread - sending the uninitiated on a wild goose chase, an expensive one at that!

Check live data, monitor sensor outputs back to DME

This CANNOT be diagnosed over a forum!

Edit - Lack of knowledge confirmed by the fact that you disconnected the temp gauge sensor rather than the DME unit

Edited November 28, 2015 by hotwire

[Andre3000 55]

Take it to Glenn, or a bmw specialist. Ron wood auto electrical in point chev are wizards with their old school tools and reasonably priced. Get it diagnosed properly.

Even the most qualified of bmw techs wouldn't be sure of a correct repair path without first doing a proper diagnosis path on the vehicle.

Could be a whole number of things ranging from temp sensors (not the sender you unplugged) to vanos units, stretched timing chains and poor compression.

Your guesstech should've sent it to a specialist after the first fumble...

[zero 1160]

+1 for taking it to Glenn.

Glenns professional scanner will be far more accurate and informative than yours, and he has decades of knowledge.

[*Glenn* 854]

I've got enough pre Christmas problem jobs ATM. The OP has probably introduced more faults now with the path he has followed. My thoughts would be along the lines of water in the DME being a E36 with all the parts the OP has already changed with no result and the reoccurring speed sensor faults. Fuel related issues would be throwing O2 sensor and fuel trim issues

[Bushmechanic 1]

I cant really get the car past new lynn. I would love to get it checked properly but do have work commitments. Unless someone knows of a good place I can go to on a Saturday afternoon thats close to new lynn.

Glen I see you are busy but would appreciate you taking a look if possible. If not I have heard of jaybee electrical which isn't far from my house and the car can make it there.

Anyone used them?

just a side note. The car has been kept in a garage ever since we have owned it. It has kot seen any heavy rain etc aside from the last wash i gave it. Surely thats not enough to allow water into such an important item?

[Bushmechanic 1]

Hi all. An update for you. The car has spent 2.5 weeks at Ron Woods. They eventually swapped out the DME as mine was damp with a known good item. The problem remained. My DME was dried and put back. The camshaft sensor was finally replaced. However the car still misfires but now additional issues are missing on low revs, not as responsive as it was before and cuts out after its been run for a bit. Misfires are not consistent. Sometimes it will and other times is won't. There were no vacuum leaks and DME seems to be fine. So what now? 2 and a half weeks, 800 bucks and a third camshaft sensor later.