528i intermittent bucking

[chiroguy]

Have a 1998 528i M52 with 300k, runs well but recently under load only, a violent bucking happens, the tach drop a bit and then recovers. Its intermittent and can happen when the car is hot or cold. Code say crankshaft position sensor and O2 sensors (pre-post cat) MAS, misfire @3. So.. Cleaned MAS, fired in new plugs (#3 was oil fouled so changed cover gasket), new CPSensor, new pre-cat O2 sensors and cleaned EGR...but engine light still on and codes are CPsensor and post cat o2 sensors

Any help would be much appreciated. Checked pre threads and responded to an old post, but this newbie is trying to get the hang of it.

[Tiger]

On all OBD2 cars, you must change all cat converter sensors at the same time. It is simply a cascade faiiure on those sensors whether you got two or you got 4 of them. They will fail short time after if you decided not to do so. It is easy to tell if you got a bad sensor or not with the scanner... look at the sensor reading... there will be fast one and slow one... the fast one is just gibberish in pattern and amplitude... it is just random whether you accelerate or not. The slow one you have to accelerate and hold the RPM and see if it changed... will be slow slow change. The dead one will simply read zero.

So if you got one that reads zero, you got to change them all or do the job 2 or 4 times. Your choice.

Where did you buy the CPS from? What brand?

You must remember that the OBD2 code is not just saying you got to change this or that... alot of time, you have to 'read between the lines' meaning if you got this code.. it is something else causing this code to appear. So do more research and test before you simply change the part out.

If any mechanic say just because you got that code, you have to change that part... Walk away fast... he will drain your pocket fast and not even fix the car.

[chiroguy]

Thanks for post Tiger.. the CPS is an Innova 3030. Ill swap out the 2 remaining sensors (the pre cat's were just installed) and see what happens. Any other suggestions?? Ive also been told that the dual mass flywheel is the culprit.

[chiroguy]

Still getting the crankshaft codes after post cat o2 sensor change... any thoughts or advice?? Maybe a harness issue??

[Tiger]

I suggest you recheck your CPS... clean out all the cogs... make sure teh CPS distance to cog is within spec and tight

[chiroguy]

sorry..
CPS?... CRANKSHAFT OR CAMSHAFT POSITION SENSOR.

ANY DIY LINKS YOU CAN PROVIDE WITH PICS ARE MUCH APPRECIATED

by THE WAY ON MY EARLIER POST WHEN YOU ASKED FOR TYPE OF cps I USED... I MISUNDERSTOOD YOU...ITS OEM, THOUGHT YOU WERE ASKING ABOUT MY OBD2 SCANNER

[Tiger]

Crank. I suggest you do a search on google or yahoo... keywords... changed CPS still engine check light BMW 528i

OEM crank position sensor... are you positive the engine trouble code is Crank position sensor or the cam position sensor?

[chiroguy]

P0335 "crankshaft position sensor a circuit malfunction"

[Tiger]

Probably your battery... check this out.

OBDII Code P0335 BMW - Crankshaft Position Sensor 'A' Circuit | Engine-Codes.com (http://engine-codes.com/p0335_bmw.html)

[chiroguy]

Happy to check the battery; its 3 years new as is the starter. What do think about a short in the wiring harness (as the 5-series has been known for trouble here) causing problem to be intermittent

thanks for your help...

[Tiger]

I really don't know... I read some other forum and the dealer said the ECM needs to be changed. If you are up to it, check out to see if the harness is shorted... or have the dealer check it out.

The battery reminds me of a case with my folk's MB... it starts perfectly fine and every single time. Not even a sign of dying battery, but a whole slew of trouble codes keep popping up almost every time we starts up the car. The only time it doesn't do that is the second starts or so. The dealer eventually did an extensive test on the battery and found out a dead cell.

So I'd suggest you test the battery... put a meter on it and start up the car and watch the lowest voltage you recorded while cranking... should be at least 10V. If you can find a smart battery tester (not an old fashion load tester).

[Katmandu]

I really don't know... I read some other forum and the dealer said the ECM needs to be changed. If you are up to it, check out to see if the harness is shorted... or have the dealer check it out. Replace the CPS first before going to the Stealership.

[Tiger]

He already did. What I am wondering is where he live... if in Arizona, I heard battery only last 3 years regardless of which one you buy.