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Old 08-18-2011, 02:56 AM   #1
1st Gear Newbie
Join Date: Aug 2011
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Game of Please Diagnose my Problem

Hi, First thank you for all who Took the time took look at this thread.

I have a 1986 325e BMW that's getting up there, but still have life in it. I'm trying to pin point a problem that i think in the end will end up being a sensor, but which..

It had the problem of kicking and lagging, and bad ( you could push the gas down and it would bogg down and sit there, spiting and sputtering, and you'd either have to ease the gas off and then on, or wait..... and then it would run perfectly fine after that point for whatever gear or as fast as you want to go ) it did it only is lower speed and gear, and only on days when it felt like it (weather/temp/ humidity- i\m not sure) ... it would run great, then it wouldn't...

More recently, that problem isn't there as much ( or noticeable ), but on simailer lines... I tried it a couple times tonight just to understand how exactly it's functioning.. it will idle normally around 600 RPM.... and then drop to around 300-400 (almost stalling), then rase to around 700 and drop to 300/400, and repeat itself.. (when it decides to do this, i smell it is running very very rich..) During this i'd push the gas so it would sit at 2000 RPM, and in the process it would drop down a bit (300/400 RPM) and sit there, poping and gurggleing a bit.... and after keeping it there for a couple seconds, it will rev back to 2000 RPM and idle at that compleately fine with no pops or anything... then i'd let go of the gas, and it would idle normally around 600 or so. but then after a couple seconds it starts reving up and down and drop to around 300/400 and back up to 700.

when it decides to run like this/ if i hold the gas while driving, just at the point that it's not accelerating, but not slowing down, the car will some times violently kick, unless i raise/ or lower the Rev.

This leads me to a sensor problem. I could be Wrong, but it just seems that way.

So i was hoping you would know which one it might be or what is is.

Thanks in Advance

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Old 08-18-2011, 07:20 AM   #2
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few things to check:

cap/rotor - check if the cap is worn or cracked, and check the rotor contact point for wear. When was the last time this was replaced as well as sparkplugs and wires? (a crack on cap and worn plugs/wires will cause those symptoms you describe)

MAF boot - chugging/lagging when pressing on gas pedal is a symptom of a cracked boot, check it and replace.

Idle control throttle valve - may be gunked up, spray and lube with sensor safe cleaner, and also clean out elect. connection and make sure it is securely connected.

check all sensor and electrical connectors to see if they are securely on.

you can also do a throttle body clean it could be gunked up.

hope that helps you out.
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Old 08-18-2011, 07:38 AM   #3
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Sounds like an afm problem.
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Old 08-18-2011, 08:50 AM   #4
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I had this engine in my car before swapping to an "i" though mine was an 85.

Have you changed your fuel filter recently? Cleaning the AFM as mentioned is very easy, make sure that flapper door moves freely inside the AFM.

Sounds like a massive vacuum leak as some have suggested. Is the intake boot torn where the clamps are? Are the bigger vacuum lines secure? Is your cold start injector leaking down?

First of all confirm the basiscs as other have mentioned about the vacuum leaks etc...
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Old 08-18-2011, 09:27 AM   #5
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Absolute worse case scenario? of course check as suggested by all means, good advice. But I had a swings in my idle as well which were really bad. and it ended up being my DME. I changed it and the car ran fine. Keep that in mind as a last thing.

I think I've had 18 bmw's in 6 years.

1 90 325is white - keepin
1 87 325i vert -red - keepin
latest addition 1 88-325is red - parts
latest addition 1 89-325i vert - white -fixin/sold
latest addition 1 92-318i vert - blue - parts
latest addition 1 87 325is blk - parts.
latest addition as of 2013-Gold 87-325is auto! it's a keeper!
KEEPER 88 5sp Vert 2016
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Old 08-18-2011, 09:43 AM   #6
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check alllll your vaccuuuuuuummmmmmmmmm linessssssssssss
R.I.P. E30
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Old 08-18-2011, 12:39 PM   #7
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Originally Posted by El Gato Liso View Post
check alllll your vaccuuuuuuummmmmmmmmm linessssssssssss
get your intake manifold smoke tested by a shop, they'll probably find some pretty bad vacuum leaks, m20s HATE vacuum leaks
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Old 08-18-2011, 04:42 PM   #8
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Hey thanks for all the replys so quickly, looks like this is a really good comunity

So to answer a couple questions in order if i can haha


-i checked the cap / rotor and points, the cap looked basicly new, the rotor was a but worn but no signs of cracks or anything, good distance. and the points had a bit of build up but nothing that i could see as being a problem ( not bad at all )

-the boot when i first got the car had a hairline crack that i just sealed with some clear rubber adhesive. i'll take off the boot and inspect it toughly

- (I think)The idle control valve is working.. but how well/or maybe not fully for all know ( i unplugged it when running and the RPM started to swing violently back and forth until i plugged it back in, so at the time i figured it was fine ) but cleaning it is a good idea, i'll get on that

-I con't find any cracks in the spark wires, ( that was my first guess ) I checked them and then misted water around all the connections and wires to see if i could see sparking/grounding but i couldn't. I'll check the plugs, and i got some throttle body cleaner the other day i'll run it through the system.

T.Dot_E30 and DR.ZED

- my second thoughts where AFM, but i wanted to chop down the basics first like you said .. i'll try cleaning it out again, and vacuum lines seems like it might be the best place to start off for the basic checks.


- Good to know, i think i might actually have a spare DME around here somewhere haha, i bought it off a friend parting his car out a year back.....

And i did find it, it's a Bosch Motronic (numbers are scratched off pretty bad ) but i think the top row say 0 261 200 027. So changing that out may be a good option as well i guess.

El Gato Liso and daveed.

- Thanks guys, that's going to be my first *go to* i'm wondering if there's a way to do a similar check at home, someone said something about spraying either or propane around the intake manifold to check for leaks, but i don't see what that would accomplish :S.
If anyone knows or has any suggestions it'd be much appreciated.

Thanks again, if anyone else has some idea's or personal experience with problems similar shout out. - and i'll try to update if i figure things out or something is beyond me haha.

Last edited by Bugsy969; 08-18-2011 at 04:50 PM.
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Old 08-18-2011, 05:38 PM   #9
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Unplug your cold start injector from the top pass side of the intake manifold to rule out either leaking cold start injector or bad thermo resistor.
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Old 08-19-2011, 02:38 AM   #10
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So i took off the intake boot and checked the vacuum lines, cleaned well and then checked for cracks. The boot is good, so are most the vacuum lines, but a couple fuel line have quite a few hairline cracks.

In the end i grabbed a can of Intake medic and pounded in half a can, and then let it run for a minute or 2...

and it started idling amazing :S...... i just can't imagen for the life of me that, that was the cure all...

So i'm going to keep it under tabbs to see if it's going to keep running well, or just going through a short spirt of good functionality...

I remember throwing in some MAF cleaner into it back in the day when i also owned a 91 325i E36 from japan thinking it was going to fix my e30 ( not realizing back then that it had a AFM and not a MAF ) and it did run better for like... a couple hours, but of course, MAF cleaner ins't going to clean out a throttle body.

Anyways, i'll keep posting . ( i have this inner feeling it's not going to be the cure [it's got age and with age, things wear out] )

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Old 08-19-2011, 05:41 AM   #11
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sounds good! maybe you should try running seafoam thru the vacuum line and really clean out the engine/afm.
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Old 08-19-2011, 12:54 PM   #12
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Originally Posted by E36is View Post
sounds good! maybe you should try running seafoam thru the vacuum line and really clean out the engine/afm.

Cool. I'll pick some up and give it a shot, thanks
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