1991 535i/5 acceleration/power problem

[240deluxe]

Hi, I have a 1991 BMW 535i, 5-speed with a dual mass flywheel. Ive always had (what seemed to be) a slight misfire, mainly a somewhat rough idle at times and a few skipped beats on heavy acceleration.

Ive also had a driveline issue, mainly the flywheel area. My car rattles when you turn it off (both with clutch in and clutch out). When you are creeping in first gear and get on or get off the gas too quickly, the flywheel area makes a loud buckling/clunking noise. When youre in higher RPMs and get on the gas (even gently) itll make the same aforementioned noise.

Today, however, I found it extremely difficult to build RPMs when taking off, especially when you start releasing the clutch. In fact, with the clutch slightly released (before engagement point), the RPMs would drop as you apply throttle. Thats when you have to push the clutch in and then build RPMs again when the engine is totally free from the transmission.

I also noticed that my acceleration was stifled, it felt like I had 60% of the power when accelerating on the freeway.

Finally, I come to an uphill onramp, and Im struggling to build RPMs to take off and finally I hear multiple clunks coming from my flywheel area and while I was moving in first gear there were a few occasional clunks as well.

I then pushed the car (barely) into a parking spot, waited a few minutes and tried first gear. Suddenly, there is no more struggling to build RPM, no more violent clunks, and my RPMs are more free than ever, its even idling a little bit higher and better.

I think its a combination of the flywheel/clutch issue as well with a power delivery issue (bad injectors, crank pos, sensor, etc.)?

Let me know guys, thanks.

This sucks because my Volvo 240DL master cylinder is bad so I have no car

[Binjammin]

Check to see if your crank sensor mount bolts are loose.

[JesterMX6]

is it throwing any codes?

i agree it sounds like a CPS issue, but there's a whole butt load of things that can cause that kind of power loss.

[Binjammin]

is it throwing any codes?

i agree it sounds like a CPS issue, but there's a whole butt load of things that can cause that kind of power loss.

My line of thinking is that he has some endplay in the crank, and a loose crank sensor mount. Push the clutch and the crank endplay pushes the trigger wheel forward... a sensor that's out of place by a couple mm and a lil bit of endplay? Stall.

[Ricky318i]

I also have this rattling sound when switching the engine off.
I'll be pulling the gearbox out soon and ill hopefully remember to post here what I found.

[JesterMX6]

the rattling sound is your flywheel. i have it too.

[stoney85]

I had it before selling my car, told the new owner.

Being a dual mass flywheel, they can lose the springs dampening between both pieces and then clunk about when you turn the car off.

A nice solution, compared to a new dual mass flywheel is to fit an E28 535i flywheel and E28 M5 clutch setup, no more soft vague clutch, and change all the selector bushes and seals while you're in there

[Binjammin]

I re-read OP's post, I had the symptoms wrong in my head. Sounds a lot more like a fuel pump for the power and a flywheel for the rattle.

[240deluxe]

I re-read OP's post, I had the symptoms wrong in my head. Sounds a lot more like a fuel pump for the power

I'm going to get a car on jackstands tomorrow morning (which is actually this morning I guess).

First of all, the CPS does seem like a good guess, however I don't think that is it. The CPS went bad on my Volvo 240DL, and basically the symptoms were: the car is either alive or dies completely, no "inbetween" or gradual dying, or hindered acceleration. That's sort of my interpretation of CPS failure, but correct me if I'm wrong please. It mainly died when RPM's were dropping and/or it got close to idle speed. For example, normally in the Volvo when the wiper motor activated, or I put in a lot of steering input, or turn on the foglights, the RPM's drop slightly because it's hogging some of the engine power. With the bad CPS, whenever I used accessories the engine would die because using those accessories brought it really close to idle (or below idle) and that caused it to die. This never happened again with the replaced CPS. Although, I will inspect the CPS tomorrow morning just to play the safe side, nothing to lose, and if I do catch that it's loose, that's one less issue I have to worry about on this intricate-ass car.

Just ordered a Bosch fuel filter off PelicanParts to see if that helps the issue at all, because I feel like the main characteristic of my problem is a fuel delivery issue, especially because when it's struggling to build RPM you can really start to smell gasoline, it's running super inefficiently. You can also smell the gasoline when the car is misfiring at idle, and the smell goes away when the idle smoothens up. Sometimes my car takes a little longer to start, sometimes it'll die the first time. This also explains my terrible fuel economy I hope. I know its a 535i but its not very good even by M30B35 standards. I'm always at the gas station. Anyways, I would love to start with the small, cheap and easy stuff (for example fuel filter) before working my way to the more expensive, lengthy repair items like the fuel pump.

Going to pull my spark plugs out tomorrow to see the condition of them, hopefully they can partially indicate how well its running. Ordered six new OEM Bosch plugs to replace while I'm at it.

Will post back here once I do all the service mentioned above, my friend with an E30 325es is having similar issues to mine, except his is dying the same way my Volvo did. Maybe he's having a fuel delivery issue PLUS a bad CPS? We're both starting out with fuel filters and working our way up.

Thanks for the feedback, guys. Will keep you posted.

and a flywheel for the rattle.

I too think the rattling is the flywheel, because it'll happen regardless of clutch in/clutch out. I did put a stethoscope to my flywheel and my transmission case, the transmission case (gearbox) was more noisy than the flywheel area, but once again the gearbox shouldn't rattle with the clutch in, so I'm assuming its flywheel.

A mechanic told me the loud buckling/clunking/pinging sound is my guibo/flex disc making my driveshaft make that "shoot a bath tub with a paintball gun" type of sound, although I thought a failing guibo/flex disc is more of a thumping/bumping sound.

I'll find out tomorrow.

[Ricky318i]

I'm going to get a car on jackstands tomorrow morning (which is actually this morning I guess).



I'll find out tomorrow.

I'm anxious to hear/see what you find. Could you be so kind to take some photos?

[JesterMX6]

if you're smelling fuel and having hard/no start issues you might be looking at a leaky injector as well. if the fuel filter doesn't fix it, might need to put a probe on the injectors and see if one is stuck open.

[stoney85]

The smart thing to do when chasing problems on a car, is to always start with the basics.

A basic service and tune up, filters, plugs, leads, rotor cap inspection etc, then delve into it from there.

I had a loose CPS on my old auto 535i a while back, the retaining bolt had worked its way loose and the car wouldn't idle, had to always hold throttle on, and occasionally it would play up in higher rpms, hit a false rev limiter sort of experience, turned out the cps was backing itself out a little and had a bit too much oil/grease build up on the face of it, cleaned it all and tightened it down and never had a drama again.

Also, check you driveline while you are under the car, the guibo has been known to disintegrate on these cars if left for a long time, also check engine mounts and trans mounts, other often overlooked wear items on these cars.

[240deluxe]

My car is running like absolute dog crap now.

https://youtu.be/SjqbsUGKwHU

(ignore the miles, the original cluster reading 140,000 was swapped for a higher-mileage one with working pixels and coolant/gas gauge).

Replaced the spark plugs and fuel filter, didn't do anything (no surprise there).

My problem is actually an electrical problem I think. Because while I was (barely) driving in first gear down my street, I got a big thump and I got all my power back, revving absolutely free and healthy, then a few moments later it went back to running like shit again. I checked my CPS, the resistance was at 538 ohms, I believe the factory value is 550 ohms. Correct me if I'm wrong.

I'm thinking it could be a ground issue, or maybe a fuel pump/DME relay. It's gotta be loose or malfunctioning, shall check that ASAP, because sometimes the situation will go back to healthy, but other times it'll go back to running like crap. However, in the long run, it has gotten gradually worse over a period of one week.

I'll let you guys know.

[Binjammin]

Check your battery connection AND the ground cable from the engine to the boody. My 535 would do exactly that when they were both loose.

[240deluxe]

Check your battery connection AND the ground cable from the engine to the boody. My 535 would do exactly that when they were both loose.

Which engine-to-ground cable do you speak of? Where exactly is it located?

Thanks for the help so far, will check the battery as soon as I remove the rear seat.

[Binjammin]

Which engine-to-ground cable do you speak of? Where exactly is it located?

Thanks for the help so far, will check the battery as soon as I remove the rear seat.

Look by the passenger's side motor mount. It should go from the mount to the frame horn.

[240deluxe]

Okay, it's been a couple months and I've made no progress at all.

I still have the same issue (see: https://youtu.be/SjqbsUGKwHU)

I've replaced: fuel pressure regulator, spark plugs, distributor cap, distributor rotor, crank position sensor, cleaned the battery terminals/grounds, I've tried a reman'd air flow meter, I've tried a second-hand ECU, none of these fixed my issue.

I was wondering if the cylinder identification sensor (also called camshaft position sensor, the one right next to crankshaft position sensor) could cause a disruption like this? Apparently it uses cylinder #6 as a reference to calculate which ignition stroke the motor is on. Maybe plug wires or ignition coil? Maybe even an oxygen sensor is making it run like shit? And don't forget the issue is intermittent, so momentarily it will run/idle fine and rev freely then back to crappy revving/idle.

I did a compression test and it came back fine, a fuel pressure test and it came back fine, and also I didn't find any vacuum leaks with hoses or intake boots, etc.

Does anybody have a clue? :/ Car has been down for two months and I'm getting fed up with it.

[Jacobw]

I'd deal with the stumble before the rattle, I've had a few dual mass flywheels that would make that clunk when I'd let the clutch out a bit to quick on a hill and bog down to low.
Bring it to the basics Air, Fuel, Spark, Main Sensors.
Test the AFM and the ICV with an ohm meter. You can unplug the AFM and it will put the dme in safety mode and you'll get a cel until you plug it back in. If it runs better that's the culprit. You can also do this with you O2 sensors.
Get a can of wd40 and spray your intake boots and your intake and if you find a place where it bogs more spray the crap out of that place till it dies, that'd be your vacuum leak. Check your booster lines and check valve too.
Check your Fuel Pressure Regulator vacuum hose. While everyone replaces the FPR itself I've seen a few people not check the vacuum line that could be leaking. If the vacuum like is leaking I've seen that kill FPR.
Make sure you have spark on every cylinder. Even though it might hurt spray your wires down with water from a spray bottle inspect for sparks, wiggle them and inspect for sparks/shocking your hand. DO NOT spray the cap or coil.
Swap your coil out for a known good one. Coils die, and I've had coils die in weirder ways than this. Seen them straight die, and I've seen them cause to bog over a certain rpm, and I've had them just get cutty on me where it feels like I'm switching the key on and off every 5 seconds while driving.
Check the resistance of crank and cam position sensors and see if the cps is loose.
If you think the exhaust if causing it drop the cat and see if it runs better (hearing protection not required but advised) unplug the O2 and see if it runs better. (will put the dme in safety mode, and you will get a cel until you plug it back in)
Also check your relays. Always check your relays and fuses on these cars. There is a few ways to test relays, but they're cheap if I think they're the culprit I go to pick-n-pull and steal a few and mark them. Test light can check all your fuses.
Make sure everything electrical is tight and in proper looking and working condition. Bad grounds can do this. Had a bad ground at my msd box that caused a miss because I got lazy and I buttcrimped and didn't solder the connections and cause a bad ground at the coil. Also had a loose positive lead at the junction box cause me to think my voltage regulator was dying.
It's hard to diagnose something from so far away. I really need my hands on it to diagnose it. The only other way to diagnose it is to find someone who had the EXACT same problem and got it fixed.

[SinisterMoose]

Okay, it's been a couple months and I've made no progress at all.

I still have the same issue (see: https://youtu.be/SjqbsUGKwHU)

I've replaced: fuel pressure regulator, spark plugs, distributor cap, distributor rotor, crank position sensor, cleaned the battery terminals/grounds, I've tried a reman'd air flow meter, I've tried a second-hand ECU, none of these fixed my issue.

I was wondering if the cylinder identification sensor (also called camshaft position sensor, the one right next to crankshaft position sensor) could cause a disruption like this? Apparently it uses cylinder #6 as a reference to calculate which ignition stroke the motor is on. Maybe plug wires or ignition coil? Maybe even an oxygen sensor is making it run like shit? And don't forget the issue is intermittent, so momentarily it will run/idle fine and rev freely then back to crappy revving/idle.

I did a compression test and it came back fine, a fuel pressure test and it came back fine, and also I didn't find any vacuum leaks with hoses or intake boots, etc.

Does anybody have a clue? :/ Car has been down for two months and I'm getting fed up with it.

Just a shot in the dark, but have you tried checking/cleaning the Idle Control Valve? That would cause an issue maintaining idle, but I'm not sure it would affect acceleration. It's possible that it's sticking intermittently, which could prevent it from idling, and make it hard to start. That shouldn't matter with revving the engine, but you've eliminated a lot of other potential problems.

The "cam" sensor on the #6 plug wire is a pretty simple system, inductive pickup (I think), but there could be some problem caused by arcing between plug wires before the pickup, which would confuse the system. This would have to be a pretty significant arc between wires which isn't outside the realm of possibility since they're so crammed together in the wire loom. It would be annoying, but you could open the plastic housing and pull all the plug wires out, separating them to make sure there is a .25" gap separating all of the plug wires and see if the problem persists.

Simply replacing all the plug wires would be the simplest way to test, but M30 plug wires are expensive because of that #6 wire with the attached sensor.

Other than these two things, or possibly a dying fuel pump, I would be stumped as well.

I had a jeep CJ5 that someone put a hand full of marbles in the gas tank, and randomly a marble would clog the fuel pickup hose, the jeep would stumble and die. I fought with it for a year before taking the tank off and discovering the marbles.

[240deluxe]

I tried a totally new AFM including the ICV, did not fix the issue.
I tried a newer ECU, did not fix the issue.
I tried the ignition coil, did not fix the issue.
I tried crank sensor, did not fix the issue.
I tried fuel pressure regulator, did not fix the issue.
I tried distributor cap/rotor, did not fix the issue.
I tried cleaning the battery and grounds, did not fix the issue.
I tried spark plugs (plus they were clean), did not fix the issue.
I did vacuum test, fuel pressure test and compression test and all came out within spec.

My mechanic said it might be injectors getting clogged or opening/closing at the wrong times.
Just googled online and OEM Bosch injectors for my 1991 535i are $85 bucks a pop... are there cheaper alternatives out there? Rebuilt or remanufactured? I'm in Southern California, Orange County.

[Jacobw]

85 dollars a piece? What stealer are you talking to? I can get 6 OEM injectors for 85 dollars. Get some ford type 3 injectors. You can get some from a 00 cobra or ford lightning from a scrapper which supposedly bolt on and are #24 and you can get them for anywhere from 60-100 dollars a set of 8. If you happen to find one at a scrapper go get some baggy pants and find some interior stuff that you need and put those injectors in your pockets. I've been doing that for years. I have a box full of 5.0 19lb injectors that I've ripped off of 5.0's or my friends 5.0's when they upgraded.

[240deluxe]

85 dollars a piece? What stealer are you talking to? I can get 6 OEM injectors for 85 dollars.

Whereabouts did you get that price? I'd like to get in on that please

And yes I've heard about the Mustang injectors, but if I can I just want to keep everything stock and OEM, unless the Mustang injectors are recommended more than OEM.

[JesterMX6]

get the 19# mustang injectors. not the 24# ones. stock is 19# and 24 requires an ecu flash to make proper use of them.

reman
http://www.ebay.com/itm/Ford-Mustang...54a21d&vxp=mtr

used
http://www.ebay.com/itm/ford-mustang...80d56b&vxp=mtr

[240deluxe]

get the 19# mustang injectors. not the 24# ones. stock is 19# and 24 requires an ecu flash to make proper use of them.

reman
http://www.ebay.com/itm/Ford-Mustang...54a21d&vxp=mtr

used
http://www.ebay.com/itm/ford-mustang...80d56b&vxp=mtr

And if I recall, they fit into the E34 535i M30B35, plug and play? What about the o-rings?

[JesterMX6]

it's been a while since i did mine. yes plug and play if you get a set like i listed with EV1 plugs. i think mine were a hair taller or shorter (can't remember which) so i enlarged the mounting holes on the fuel rail. IIRC i used the supplied o-rings when i got mine. (used set, purchased off a mustang guy locally)