Rough & Misfiring RPM, need advice. [Archive]

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takumidrift30

10-19-2006, 02:28 PM

This is actually a continuation of my previous thread, decided to have a separate one. Anyway here it goes, basically got her just last week-1992 525i 5 speed (M50), was garaged for 4 months w/o starting, we only started her when we pick her up. Had a rough idle sound actually more like a misfiring from idle 'til 3,500 RPM, standing rev and moving. After 3,500 RPM as if nothing is wrong with it 'til 6,000 RPM.
Here's what I did:
1. Put new plugs
2. Bought 3 new ignition coil (As the previous owner says that it needs 2 igniter guess he meant coils upon testing found that it was 3).
3. Put new fuel filter, Fresh gas and injector cleaner.
4 Checked all the hoses & vacuum for leaks-found nothing everything is ok.

Results: for the few miles got a better idle and the misfiring like thing went down from idle to 2,000 RPM. As I used it today it went back to the same condition as when I got it. Rough idle at low RPM and misfiring like sound at high RPM. Planning to do today compression test.

I would appreciate any input at this point, thanks in advance!

stu1

10-19-2006, 03:24 PM

Might well be worth just giving it a bit of a clear out. Get it out on the highway and just run it at 5000 rpm in 3rd gear for five minutes or so. Occasionally drop it down to 4000 and then hard accel up to 6000, then back to 5000.

DABLACK

10-19-2006, 03:53 PM

were the coils (old) cracked or did they burst?
usually when this happens it messes up the dme/ecu
whatever whoever calls it (engine comp)
you might have to get a new one
just a thought I went through the same thing
check it out and let us know

good luck!

632 Regal

10-19-2006, 03:58 PM

this sounds crazy!
Might well be worth just giving it a bit of a clear out. Get it out on the highway and just run it at 5000 rpm in 3rd gear for five minutes or so. Occasionally drop it down to 4000 and then hard accel up to 6000, then back to 5000.

BillionPa

10-19-2006, 11:31 PM

you might want to check the battery and alternator before you go high RPMs on it, and also do the plug boots on the other coils.

O2 sensor good?

VentoGT

10-20-2006, 09:19 AM

Check the cap and rotor for moisture or corrosion...sounds like it well could be the culprit. You may not be running on all cylinders either.

acidfire52

10-20-2006, 10:24 AM

I have this same problem with my M50. Mine also sat for several months before I bought it.
When I bought the car 2 months ago I do not remember the problem. Seems it started when I replaced the plugs with Platinums. Found out they such, replaced with copper plugs, still does it.

Was thinking it could be a problem with my VANOS. Does anyone know how to check to see if that is working?

Have also read it could be the MAF. Tried unplugging that, but it just ran worse.

takumidrift30

10-20-2006, 11:40 AM

Thanks for the input guys! The O2 sensor is good, changed the boot plugs and the rest of the igniton coil-so basically all 6 coils are new, cleaned the throttle body and still the same. I did a compression test and the results were good w/c i wasn't expecting consistently at 200 psi except for #1 w/c is 190, but that is still good right?
Also I noticed as the engine temp. gets higher the roughness gets worst.
noticed also with the new plugs when I removed them, the tip or codes are dark (these are new plugs) so I would assume at this point that she is running rich?
Guys need your help how to address this problem, it's getting kinda frustrating at this point. Thanks again!

takumidrift30

10-20-2006, 11:41 AM

you might want to check the battery and alternator before you go high RPMs on it, and also do the plug boots on the other coils.

O2 sensor good?
The battery is new too.

acidfire52

10-20-2006, 11:54 AM

My battery and alternator are both new too. :)

BillionPa

10-20-2006, 11:17 PM

he has coil on plug ignition, no distributor.

check the running voltage from the alternator, should be something like 13.8 and stable.

the MAF could be suspect, is it the original?

do a fuel pressure test to see if the regulator is working, a rupture could cause excessively rich idle and running under low RPM situations, but go back to normal as the RPMs increase.

Paul in NZ

10-20-2006, 11:37 PM

make sure the coolant sensor for the computer is right,if its no good will make it run rich which will be ok cold but not as it warms

stu1

10-21-2006, 02:15 AM

this sounds crazy!
:)

My thinking is that if it's been sat for four months (and it was working OK before it got laid up) then its possible the valves and in particular the injectors have become gummed up and are not sealing properly. Now if there's any carbon deposits in there, with leaky injectors and valves it could get pretty bad.

Stu.

acidfire52

10-22-2006, 01:10 PM

I just finished a tank of BG 44K. Don't think it is build up on mine.

I think I am going to try some spark plugs from BAVAuto. I really don't think my car had the issue before I started messing with the plugs.

Also, is there a way to see if the VANOS is working properly?

VentoGT

10-23-2006, 09:48 AM

he has coil on plug ignition, no distributor.

Okie Silly-illy dokie yo, I'm an idiot :D

takumidrift30

10-23-2006, 04:45 PM

Ok checked basically almost everything, check the current coming from the alternator and all the sensors, did a pressure test on the fuel system, changed all the injectors even the good ones might as well since I have plans of keeping her and still same thing.
Gave up brought it to any indy and did all the diagnostic test and said that it was the box, so at this point I'm looking for a used computer (5 speed manual) 1992 525i. I don't have the part # with me right now have to drop by or call the shop to get but if there's anybody who knows who has selling I would greatly appreciate it. Again guys thanks for your input, I'll post also on the classified ads section, once I have the part #.

takumidrift30

10-23-2006, 04:48 PM

By the way, do you guys have any idea how much it would cost me or atleast a decent price range for a used one?

acidfire52

10-25-2006, 01:37 PM

takumidrift30

10-25-2006, 04:44 PM

You will have to let us know if this fixes you problem as I am at the same spot as you I think.

Good Luck

Acidfire, put on today the new box well, I guess that was my problem after all. She's perfectly ok now, running smooth and strong. For curiosity sake, I tried putting back all the parts I replaced with the new box and it was still ok. Guess it was the box after all, looking at it from a different perspective it is still good that I checked and did all diagnostic atleast I now have more peace of mind and feel good about her. You might want to check your box too if you have the same issues.
Guys, thanks again for all the input really appreciate it.

acidfire52

10-25-2006, 05:34 PM

Acidfire, put on today the new box well, I guess that was my problem after all. She's perfectly ok now, running smooth and strong. For curiosity sake, I tried putting back all the parts I replaced with the new box and it was still ok. Guess it was the box after all, looking at it from a different perspective it is still good that I checked and did all diagnostic atleast I now have more peace of mind and feel good about her. You might want to check your box too if you have the same issues.
Guys, thanks again for all the input really appreciate it.

Now, did you get another box with the same number? Does it matter what year I get it from? I am guessing I have to have a '93+ one as I have VANOS.

takumidrift30

10-27-2006, 12:32 PM

Now, did you get another box with the same number? Does it matter what year I get it from? I am guessing I have to have a '93+ one as I have VANOS.

Fortunately for me I was able to get a box of the same serial #. I'm not really sure if it's ok not of the same serial #, I would assume it's ok but if somebody more knowledgeable can give us advice.