1992 525i project runs rough

[wiebuschk]

1st let me say this is a Great forum. The wealth of knowledge here is incredible. I have learned a ton about my car just from searching. I was previously signed up as Buschman but could never post for some reason.

Here's what we have. 1992 e34 with the m50 engine & a 5 speed. This is a project that was for my 15 year old son & I which we bought for $350. It's not real pretty but the leather was good & it ran & the AC worked.

We have put in a clutch, A rear bearing, A general module for a door lock & window problem, & a center tie rod. We are still OK money wise but we probably won't have any body work done. It is now inspected & street legal.

It doesn't run as smooth as it should. It bogs down & almost shudders in low rpm. If I am in 5th gear going 65mph & floor it it just shakes & slowly speeds up. It idles fair but not like it should. 5000 to 7000 rpms feel pretty good. It seems to run a little better when it's cold. I can feel it miss sometimes & then smooth out. I get an occasional intake backfire.

Car has over 180# compression in each cylinder. It has new plugs. It has 17 inches of vacume at idle.The old plugs looked great. A BMW mechanic told me if it was a vacume leak that was bad enough cause this much problem it would throw a check engine light & a code. The only code is a 1444 which means there are no codes. I have run one can of Techron through it but plan to run more. I do think the car sat up for a while. The TPS checked ok with a meter.

I have previous experience rebuilding a 1985 K100 rs bike which ran like ass until I cleaned the injectors so I am leaning this direction.

Any good ideas? Thanks in advance!!

[Jon K]

You failed to mention the mileage but some things I would check:

I would suspect perhaps a leaking injector. If you're getting back fires in the intake that is most likely the culprit I would think - the car is sequential injection but the OBDI aspect makes it impossible for it to detect misfires. 17" is decently good for a '92 525 mine holds about 17 - 18". The only thing is, for a backfire to happen in the intake the timing could be off but I am not entirely sure - it could be running lean on one cylinder and heating the valve and the fuel igniting that way - not entirely sure.

I'd like to know how many miles are on it though. The fuel reail is S I M P LE to pull so it'd be a good idea to pull it and have a look see.

[632 Regal]

you covered most of the bases, thanks for the searches. I would recommend a computer reboot which will set all codes gone and you will have fresh to start with. If the codes are never reset the same issue will traspire even tho you replaced the failing items indicated. Wait after you reboot the computers and post again, hopefully your troubles will go away.

good luck and the best.

[wiebuschk]

If rebooting is unhooking the battery for 10 minutes & hooking it back up, I've done that. The car has 180k. I have sprayed wd40 around the injectors when running & it does not speed up. My thinking is that when it runs bad it is under a load so vacume would do higher. Maybe that is when the vacume leak occurs.
By leaking injector you mean an air leak around the O-ring seal?

[jjdickm]

a leaky injector usually means it is not closing the valve completly and you have un measured fuel going into you engine. causing one of you cylinders to run extemley rich. If thats the case replace the injectors and your car will run fine. The thing that bothers me is you said the plugs looked good. I would probably try to find the manifold leak. check all the intake boots for any cracks or gaps. Good luck!

[scott 4991]

Some thoughts - plug wires? Dist cap? O2 sensor? I recently ran a vacuum guage out the back part of the hood and taped it to my windshield, just to see what the vacuum was doing. MAS - checked? There is a procedure in the Bentley book, looking for a glowing wire - I have not done, but read about. What about the center bearing (in the driveshaft) and the engine and transmission mounts - easy to replace, just did mine.

Keep us posted.

sc

[kesslerbmw]

I am having a similar problem, my car will start missing bad on one or even two cylinders (4&5) and I thought it was coils. I swapped the coils, ran ok for a day or two, problem came back, swapped the plugs. Ran ok for a day or two and the problem came back. I havent jacked with the injectors yet, but Im going to try when it warms up around here.

Have you cheked the coils? Doesn't seem likely, but it may be worth a check.

Also you can use an ice cube on the exhaust manifold to pinpoint which cylinder that is giving you trouble. Obviously the cylinder that is missing will not melt the cube nearly as fast.

[tree18is]

i wish i could help you out... always good to add a fan to the bimmers.

[Jon K]

Some thoughts - plug wires? Dist cap? O2 sensor? I recently ran a vacuum guage out the back part of the hood and taped it to my windshield, just to see what the vacuum was doing. MAS - checked? There is a procedure in the Bentley book, looking for a glowing wire - I have not done, but read about. What about the center bearing (in the driveshaft) and the engine and transmission mounts - easy to replace, just did mine.

Keep us posted.

sc

No plug wires, no dist cap. These are coil on plug cars. If his coils were misfiring frequent enough his plugs would be carboned up.

It's either a leaking injector (Leaking fuel, not air) that puddles on the valve more than it's intended and igniting, causing the backfire out of the intake, or its a vacuum leak doing the same.

Nothing about the driveshaft or engine mounts would cause this.

I know it sounds like a big job, but remove the intake manifold and buy new O-ring gaskets for the intake manifold (they're relatively cheap). They tend to get weird at around 150k. I replaced mine. I used to have a backfire in the manifold as well. No more.

If that doesn't do it, look for cracked or damaged throttle boot and ICV lines etc - if you backfired enough you could have cracked anythign plastic or rubber.

[wiebuschk]

Thanks again for the replies gentlemen. I have been tempted to pull the intake just to check the vacume lines & clean up the ICV beneath it anyway.I didn't know what kind of gasket I would run into. Is RTV against the law for this application? It works on GM's & Fords>

When an injector leaks is it because it's gooped up or is it faulty?

BTW I just love the way this car drives. I would like to get a touring version someday!