CRAZY M44 Problem

[WhoNew]

Hello there, I am having an issue with my 96 318/M44.

Okay, it runs and drives absolutely perfect...... until it hits 5000 RPMs. At 5000 RPMs, almost exactly, it feels as if it is hitting a rev limiter. The car just bounces and surges, but will NOT rev above 5000 rpms. I reset the computer, and as long as I drive the car and keep the RPM's below 5000, it is perfect, no check engine light.

If I keep on the gas till 5000 RPMs, and it surges, the Check engine light will come on. (it actually will go off and on as it bounces from 5000 down to about 4500 RPMs). then it's on. I had the codes pulled, and it said it was the Crankshaft position sensor. I reset the computer, drove it nice, and no CEL. so then, I get on a nice long stretch of road, and get it up to 5000 RPMs to see if I can MAKE it get past. Gas pedal to the floor, it just bounced from 5000 to 4500 RPMs for like 30 seconds. This not only threw the CPS light, but codes for the knock sensors too.

So am I too assume that the crank position sensor will cause this ?
I thought if the crank sensor was bad, the car wouldn't even start.

Any help would be greatly appreciated here. Thanks.

[Bobbak]

change the sensor and it will fix the problem


i thought my knock sensors were bad and my car was knocking really bad so i changed the sensors and it still didn't fix the problem but after about 8 months of troubleshooting i found out it was the spark plugs so just change the most obvious things and it will be fixed

[marko]

change both sensors, just in case... not too expensive & even if it does not fix the prob (which it most likely will), you eliminated 2 things that often go bad.

[mohaughn]

The 5k redline is a safety feature I'm pretty sure... I know the engine will go into a safe mode and keep you from revving beyond a certain point. It usually does this when you have a bad sensor, like others have mentioned.

[WhoNew]

HMMM..... one of my BMW buddys suggested it sounds like a computer induced "limp" or limiter.

I really hope it's not the trigger wheel. OKAY, I'll change the CPS, and see if it fixes the issue.

[WhoNew]

okay so more than 3 months later i have the issue figured out

it's the 40 cent o-ring. the PO obviously got the wrong o-ring to fix an oil leak or something. it was the o-ring for the cam sensor which is about 3 times as thick, and does not sit on the recces provided, it held the cps ABOUT 1/4 INCH TOO HIGH so the sensor could not read at higher RPM's hope this helps someone out there !!

[cooljess76]

WOW! congrats on figuring that one out. Man, I would have never guessed that would be the problem.

[WhoNew]

i talked to the guys at the bmw parts counter when they ordered my crank sensor, after they handed me a cam sensor...... I told them it was the wrong part, and the guy said it happens all the time cuz bmw calls both the cam and crank sensors "pulse generators". he said it's easy to get it wrong in the computer.

That got me thinking about it, and when i removed the original sensor the mounting plate was bent. thought it was just offset original. it wasn't. when I got the new o-ring and sensor, i knew EXACTLY what it was. I wish I would have taken pics, but it is such a huge pain to do, i just wanted to get it done.

I searched and searched, but found nothing, so i hope someone else has a questioning attitude next weird issue they run into. the worst part is it cost me well over a hundred bucks and a few hours in the driveway, and months of aggravation for a .40 cent O-ring. AND i hate when people post an issue and don't follow up on the solution. that pisses me off.

[Mallard]

i talked to the guys at the bmw parts counter when they ordered my crank sensor, after they handed me a cam sensor...... I told them it was the wrong part, and the guy said it happens all the time cuz bmw calls both the cam and crank sensors "pulse generators". he said it's easy to get it wrong in the computer.

That got me thinking about it, and when i removed the original sensor the mounting plate was bent. thought it was just offset original. it wasn't. when I got the new o-ring and sensor, i knew EXACTLY what it was. I wish I would have taken pics, but it is such a huge pain to do, i just wanted to get it done.

I searched and searched, but found nothing, so i hope someone else has a questioning attitude next weird issue they run into. the worst part is it cost me well over a hundred bucks and a few hours in the driveway, and months of aggravation for a .40 cent O-ring. AND i hate when people post an issue and don't follow up on the solution. that pisses me off.

strange really, because BMW dont´"call" anything at all, its ALL done by numbers!

so if the guy gave you the wrong one, its because he didnt know what to look for..

im glad you got it sorted out fella :)

[speedracerf4i]

My problem is as yours, but my rev limit is only 2K.

I was driving on the freeway yesterday and all of a sudden, I lost power (50%). The engine still runs as if I was driving in neutral. A cell came up in which I found out to be "cylinder 1 misfire".

I was able to slowly drive home at max speed of 40MPH (5th gear) with my emergency blinkers on. There is no hesitation on the engine at all, just feels like there is a long accerelation lag and driving a 20 HP car.

I checked the spark plugs and they are firering OK, though the spark was kind of weak. I am not sure how strong the spark had to be. The engine was idling fine at 800 RPM smoothly even with 1 plug off.

The exhause smelled like unburned gas and from searching, I narrow down to a few culprits.

1. Spark plugs - I checked all 4 and they are firering (pulsating).
2. Plug wires - If the plugs are firering, can the wires still be bad?
3. Ignition coil - I am getting sparks and there is no hesitation on the engine. Can this be bad?
4. ECU - This is an expensive unit with no way to tell if this is good or not right?
5. Fuel injectors - The unburn smell may suggest that it's delivering fuel OK. Will this throw a cell if bad?
6. Cam Position sensor - The engine has no weir vibration though. And I didn't get any cell related to this.

Maybe I am missing something else. Please help!!!

[DustenT]

My problem is as yours, but my rev limit is only 2K.

I was driving on the freeway yesterday and all of a sudden, I lost power (50%). The engine still runs as if I was driving in neutral. A cell came up in which I found out to be "cylinder 1 misfire".

I was able to slowly drive home at max speed of 40MPH (5th gear) with my emergency blinkers on. There is no hesitation on the engine at all, just feels like there is a long accerelation lag and driving a 20 HP car.

I checked the spark plugs and they are firering OK, though the spark was kind of weak. I am not sure how strong the spark had to be. The engine was idling fine at 800 RPM smoothly even with 1 plug off.

The exhause smelled like unburned gas and from searching, I narrow down to a few culprits.

1. Spark plugs - I checked all 4 and they are firering (pulsating).
2. Plug wires - If the plugs are firering, can the wires still be bad?
3. Ignition coil - I am getting sparks and there is no hesitation on the engine. Can this be bad?
4. ECU - This is an expensive unit with no way to tell if this is good or not right?
5. Fuel injectors - The unburn smell may suggest that it's delivering fuel OK. Will this throw a cell if bad?
6. Cam Position sensor - The engine has no weir vibration though. And I didn't get any cell related to this.

Maybe I am missing something else. Please help!!!

Check your intake boots. The rubber boots that connect your airbox to the rest of the intake system have a tenancy to dry out and crack. Wiggle them around, if they look dry rotted, replace them.

[speedracerf4i]

I sprayed a fine mist of water around the intake boot, but there was no disturbance. So I don't think my boot was the culprit.

[jnande4176]

water, on your intake boot?! You need to spray brake cleaner all around the boot and listen to the engine. If you are spraying it and you notice that the engine magically begins to run silky smooth or idling a little higher, then you have a cracked intake boot. Also, if your scanner can, check the lambda levels. These will show you your O2 sensor readings in real time.

[speedracerf4i]

OK, I'll give it a try.

I have reset the "cylinder 1 misfire" and I'll drive it on my neighborhood streets some more to see if anymore codes would come up.

I have the Bently manual and I will go through all the trouble shooting check list for ignition, and fuel delivery if no cell ever comes up again.

[jnande4176]

Sometimes, on cars with individual coils, a cylinder misfire can indicate a faulty coil, or possibly spark-plug. You should check your plug wires. Swap plug wires with another cylinder and see if it throws a code for a mis-fire in the cylinder you swapped the plug wire to, i.e. take plug wire from cylinder 1 and swap it with the wire from cylinder 3. If you get a code for misfire cyl. 3 then you have a bad plug wire.

If you are not firing, the lambda reading will be ridiculously high because it will detect un-burnt fuel in the exhaust. If you have the capability to check it, that would help narrow things down.

Another thing you might want to consider is check the gap on your plugs.

[pdxmotorhead]

When the air boot cracked on my car you had to take it off the car to find it the normal spray method did not do it.

Dave

[FRENCHCONNECTION]

speedracerf4i, i got the same problem that you had, did you fix your car? if you did? what was wrong with it? plz help me

[speedracerf4i]

speedracerf4i, i got the same problem that you had, did you fix your car? if you did? what was wrong with it? plz help me

OK, I narrowed it down to a bad MAF.

According to Bently manual, a bad MAF will make your DME to go into "Limp" mode. My ignition, fuel delivery, emission, all are normal. So I am buying a used maf to see if it cures the problem.

Stay tuned.

[speedracerf4i]

I just replaced the MAF I bought from Marvin.

The car is still in Limp mode. no luck...

I will take to the shop and let them figure out what's wrong

[speedracerf4i]

I tested the ignition coil with the a voltimeter and found out the the resistence was between 10-14 miliohms. According to Bentley, it should be 4-8 mili-ohms. I also found hair-line cracks on my coil so I am replacing the ignition coil and the plug wires to see if they will get me out of this limp-mode.

[jnande4176]

Yeah, that sounds like a good plan. Let us know what happens.

[speedracerf4i]

My mystery has been solved!

I finally towed my car to a shop and after going over all the possible causes and came up fine.

The problem, as it turn out, was constipation. My catalytic converter was plugged up!!! Thus restricting exhaust from going out...

I heard that DEC can no longer sell a 50 state legal cat, so I guess I need to buy the OEM cat now.