Author Topic: M42 Engine faults Cutting out at 4500 RPMs (Read 13628 times)

Broach318 · « **on:** February 11, 2013, 03:07:32 PM »

FIXED!! SEE MY LAST POST FOR SOLUTION!

Hello everyone this is my first post to this site. I have searched everything I can and would really like some advice from people who know the M42 motor!

Here is the story I have a 91' 318is. We recently went through pulled the motor, tranny and replaced about everything. It ran amazing for about 8 months, fuel pump went out about 3 months ago I replaced it with OE pump along with filter. Car ran perfect now about a month ago, out of the blue it starts acting up. After the car is warm it will cut out RPMs around 4500 and seems to just run horrible just sputtering out sporadically like its just not getting fuel, which the fuel pump and filter are brand new. Also it starts fine when cold but after its warm and sits for a few minutes it takes about 10-15 turns before it starts, also started out of the blue at the same time as the other problem. Did the stomp test got the bad o2 sensor code 1221. So I got a new o2 sensor, same thing. So we got a new FPR, started it did and drove to get fuel 15 minutes away. It did the same thing. Got the gas and left and it ran perfect smooth pull up to 6300RPM all gears. The next day it does fine. The next day its back to running like crap again. I am absolutely baffled and frustrated to no end. If anyone could lead me in the right direction i would be greatly appreciated! Thanks so much advance guys!

romkasponka · « **Reply #1 on:** February 11, 2013, 05:35:56 PM »

One my colleague had similar problem and after few months fight he found front pulley http://bmwfans.info/parts/catalog/E36/Coupe/Europe/318is-M42/browse/engine/belt_drive_vibration_damper-2/ part #1 which is with rubber damper and at certain revs it starting to vibrate and give faulty signal to the engine ECU. Hope it will help

DesktopDave · « **Reply #2 on:** February 11, 2013, 05:53:42 PM »

I had a few ideas, nothing specific though.

Check to make sure the fuel supply and return lines aren't swapped at the intake manifold.
Check for vac line leaks.
Check coolant and air temp sensors. They should have very high resistance when cold (10K Ohms IIRC) and very low when hot (300ohms?).
Check fuel pump and main relays with a jumper to see if the problem goes away. Sometimes they age a bit and don't give 100%.

Broach318 · « **Reply #3 on:** February 11, 2013, 07:55:35 PM »

Okay I will look into that, I was leaning towards the CPS ( cam position sensor)? what do you all think? Its just super weird, two days ago it runs 120% and the next day its running like crap. I just don't get cars sometimes :/

DesktopDave · « **Reply #4 on:** February 11, 2013, 08:32:41 PM »

You said that this only happens when it's running warm, right? In that case your DME might be stuck in the warmup loop & injecting way too much gas for a hot motor. So I'd suspect the closed-loop sensors like CLT, IAT, TPS and associated wiring.

Our cars are famous for intake manifold leaks too. The rat's nest of vac lines under the manifold is the usual culprit. Eliminating the TB preheater and associated Medusapalooza is a well-tested preventative.

I've also noted the occasional bad plug wire or coil. Typically that will only happen when they overheat. Troubleshooting the coils is a PITA, easiest to check the plugs for one that's different and then swap a known good coil pack and see if the problem persists.

The car will go back to open-loop at wide-open throttle...when the car is bogging, can you fix it by flooring it?

inarticulate is · « **Reply #5 on:** February 12, 2013, 01:04:27 AM »

Had similar symptoms with a Mercedes, was the mass air sensor being twitchy.

Broach318 · « **Reply #6 on:** February 12, 2013, 11:48:49 AM »

@ Dave, Correct it only does this when it gets warm. No its like it is literally hitting a rev limiter at 3-4500 RPMs its sporadic which makes it very odd. Changed the spark plugs a few days ago and did nothing.. Mass air flow was sent to a guy to be rebuilt and we checked it and it is working fine. I will look into some of the vac leaks in and under the manifold. Thanks!

Broach318 · « **Reply #7 on:** February 12, 2013, 02:51:37 PM »

An update today I drove it around trying to figure out the cause. At first it ran okay (car runs okay until it warms up to running temp and thats where it begins. The higher gear you are in the lower the RPM will cut out, 2nd is around 4 3rd is 3500 4th is about 25-2800 and 5th is anywhere from 1800-2300) so I did the stomp test. It throws a code only in 5th when its bogging out bad and its 1221 for the oxygen sensor, which is new. So I unplugged it and it ran perfect, very smooth pulls all the way to 6300 in all gears (1st,2nd,3rd) drove it for another 10 minutes or so cut it off let it sit for 10 minutes. Started it up ( still does not want to start like it should) and it drove perfect with the O2 sim still unplugged. I got to a stop sign plugged it back in, and it still drives good. Although not quit as good as unplugged, it still went to 6300. Just personally didnt feel as strong as when it was unplugged. I took some videos, I will post them when I figure out how to get them on here. Thanks a lot guys, all input is really appreciated.

Broach318 · « **Reply #8 on:** February 12, 2013, 03:00:31 PM »

http://www.youtube.com/watch?v=AHrhHLXcP38

This video shows the bogging out. ^^

http://www.youtube.com/watch?v=ELrT2gGckgc

This video is after I unplugged the O2 sensor

Broach318 · « **Reply #9 on:** February 12, 2013, 09:56:36 PM »

I posted two videos, its telling me a mod has to review it first... But anyways Ive been researching on this for hours now. And Ive found a few possible solutions. The spark plug wires, AFM, crank sensor. Other than that I really have no clue, as the fuel pump, filter, FPR are all new, and we just pulled the motor and fixed everything. ( 8 months ago). All of this happened overnight, ran great and that next day was 180* difference.

DesktopDave · « **Reply #10 on:** February 13, 2013, 04:46:52 PM »

You're making some progress! BTW - I approved your posts & deleted the duplicates. The site has a lot of trouble with spammers so the filters are pretty tight...sorry for the inconvenience.

Here's my thoughts...I suspect the O2 sensor is OK, but it's reading out-of-range...probably too rich.

Humor me & put a multimeter on that coolant temp sensor both when it's cold and when it's warmed up. Let me know how many ohms it's putting out. If the CLT is bad it'll tell the DME that the car isn't fully warming up, so the DME compensates with more fuel - running a pretty rich mixture especially at high RPMs. In that case you'll get a 1221 as the O2 reads really rich.

Alternatively, intake air leaks or even a bad ICV will cause O2 codes - the unmetered air leans out the fuel mix and you get a 1221. Plugged fuel injectors can do the same thing.

By any chance you haven't recently sealed the intake or exhaust with a silicone RTV, have you? Some of those silicone make-a-gasket sealers can damage O2 sensors.

Broach318 · « **Reply #11 on:** February 13, 2013, 07:48:51 PM »

Yeah, its just getting frustrating. Okay well i checked the coolant sensor got 2.250 OHMS while car was cold, as it warmed up it slowly dropped, so thats good. Today I drove it trying to figure it out, and was worse even cold it would barley go over 1500 rpms and actually have zero spark. I could give it full throttle and would completley bog out. got the check engine light, stopped on the spot and did the stomp test and got the 1221. So I unplugged the O2 sensor and it ran better not perfect by any means but enough to get on the road and drive, like it runs good until you get to a certain rpm or load and it just like its getting the fuel cut to it.

keflaman · « **Reply #12 on:** February 13, 2013, 08:09:55 PM »

Quote from: romkasponka;120017

One my colleague had similar problem and after few months fight he found front pulley http://bmwfans.info/parts/catalog/E36/Coupe/Europe/318is-M42/browse/engine/belt_drive_vibration_damper-2/ part #1 which is with rubber damper and at certain revs it starting to vibrate and give faulty signal to the engine ECU. Hope it will help

And here's another thread with "cuts out at XXXX RPM". Turned out to be the harmonic balancer just as romkasponksa suggests.

http://www.m42club.com/forums/showthread.php?t=14814

Broach318 · « **Reply #13 on:** February 13, 2013, 08:11:54 PM »

@keflaman did your car have the same symptoms as what I am experiencing? Or what symptoms did you have exactly? Thanks!

keflaman · « **Reply #14 on:** February 13, 2013, 08:54:43 PM »

It wasn't my car, but I picked that thread specifically because it was one of the few that the OP actually posted the resolution. I dunno, maybe the rubber compound has more give when it's warm and it's throwing the timing off; when everything cools the rubber firms up and timing is correct.:confused:

Based on that theory, everything is copacetic and you're tootling down the highway. Meanwhile, the rubber in the harmonic balancer warms up by heat in the engine compartment and becomes more pliable. When you accelerate the crank speeds up, but drag induced by the AC compressor and alternator belts distorts the rubber and that throws the timing off and the DME retards or shuts down the engine.

The car is parked for some time, everything cools down and the car magically starts up again running fine and then...

Just some food for thought: What part of the country do you live in? Have you experienced any wild temperature swings? We've gone through a couple cold-hot-cold days with 30-40*F temperature variations.