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3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

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Old 08-06-2008, 10:36 AM   #1 (permalink)
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car hiccups at 1500 rpm's

Tried posting this in another forum, but got no help, so let's try here...


So I've spent the last month or so fixing up the m50 in the 1992 325i I just bought. Had to replace the head, and do a few other things to get the car running again. Once I got the car to fire, it just wouldn't idle. It was spitting & sputtering like crazy, but once the revs were up, it was singing beautifully.

After some searching I found a vaccuum leak from the intake (somehow I missed one of the gaskets during the re-install ) So I ripped the engine apart again, replaced the gasket & got everything back together again. The car will idle now; still a little rough but definately better.

But the problem I have is this... at 1500 rpm's the car dies! Not totally stall out (sometimes it will though) but it feels like the car totally cuts off. push the gas a little harder & it'll rev up just fine & act like nothing's wrong. But it won't hold revs at 1500. Same when you're trying to drive it. Once the car reaches 1500 it noses over hard & sits for a second before it takes off like a scared rabbit!

Is it possible that it still has a vaccuum leak someplace that I haven't been able to find? Or is it maybe something else like an o2 sensor?

Any help would be hugely appreciated! It's really hard to drive in the state it's in now!
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Old 08-07-2008, 09:03 PM   #2 (permalink)
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bump!

Really need help with this one! It's too hard to drive the car this way!

Anyone?
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Old 08-07-2008, 09:30 PM   #3 (permalink)
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Doubt it is a vacuum leak... sounds more like an O2 sensor or MAF. Something about the air/fuel ratio at that rpm not mixing right... do you get a check engine light at that rpm?
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Old 08-08-2008, 08:40 AM   #4 (permalink)
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I had it throw a CEL once, but not since. It was code 1222 - oxygen sensor lean/rich control stop.

Bentley says something about check intake for air leaks; which was when I found that seal missing. Haven't seen the CEL since, but car is still acting up!

Would changing the o2 sensor be a logical next step?
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Old 08-08-2008, 09:22 AM   #5 (permalink)
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Lightbulb

check fuel pressure.

and then after letting your car idle for 15 mins, pull out a plug and check the color of the burn. u should get a light brown to a light ash gray color. It's also a good time to inspect your wires/boots for tears or cracks.

too dark, is a rich burn; too light is a lean burn(not enough fuel or vacuum leak)

*TIP: low end sputter/hesitation is oftentimes attributed to failing spark plug wires or spark plug boots, as the case may be

Last edited by darkhorse737; 08-08-2008 at 09:24 AM.
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Old 08-10-2008, 09:37 PM   #6 (permalink)
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get the car moving in first gear and try to maintain the 1.5k rpms (or whatever rpm you are getting the problems at) keep it at that rpm for... say 5 seconds (if you can without it dieing). If it is the 02 sensor you should get a check engine light. Also, follow the steps recommended above.
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Old 08-11-2008, 09:31 AM   #7 (permalink)
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gonna change the plugs today & then disconnect the battery & try and relearn the idle speed. Don't think it'll help but can't hurt. Also found out today that I missed an o-ring on my oil dipstick tube that I'm gonna replace too; but I doubt that's causing this much trouble.

Will try to run the car at 1200-1600 rpm sustained after changing the plugs later; but any time I've been in that area before the car bucks pretty violently; and wants to stall out, which is why I get on the gas pretty hard to drive through it...
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Old 08-11-2008, 09:40 AM   #8 (permalink)
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gonna change the plugs today & then disconnect the battery & try and relearn the idle speed. Don't think it'll help but can't hurt. Also found out today that I missed an o-ring on my oil dipstick tube that I'm gonna replace too; but I doubt that's causing this much trouble.

Will try to run the car at 1200-1600 rpm sustained after changing the plugs later; but any time I've been in that area before the car bucks pretty violently; and wants to stall out, which is why I get on the gas pretty hard to drive through it...
u might have something in that missing o-ring. thts actually enough to cause an intake leak through the positive crankcase ventilation system

anyway, after u'v done that and the prob is still there, consider the Throttle switch. There might be a break in the internal potentiometer.

lotsa' luck to u
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Old 08-11-2008, 06:24 PM   #9 (permalink)
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well, changed the plugs... one plug was totally wrecked. didn't help. found that one of the coil boots is cracked about 1/2 way up which will need to be replaced. Still have to get an o-ring for that dipstick tube.

tried running the car down the road in 1st at 1500 rpm's: car would go smooth for maybe 2 seconds;then engine acts like it dies; a couple of pops out of the exhaust (I swear a few times I heard it burp through the throttle body) then it would go again for a few seconds & repeat. Did that for about a half mile (what a jerky ride that was!!). No CEL.

When I got home I sprayed every crevise, hose & fitting I could find with throttle body cleaner looking for the vaccuum leak, but nothing seemed to smooth out or choke out the rpm's...
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Old 08-11-2008, 10:15 PM   #10 (permalink)
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I'd go with Darkhorse for now on this... I was hoping you were going to get a light. Do you have access to a Bently manual for your car?
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Old 08-12-2008, 10:09 AM   #11 (permalink)
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yeah, I've got a copy of it on my computer. I've been in & out of it a few times now looking for answers...
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Old 08-12-2008, 06:43 PM   #12 (permalink)
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well, found an o-ring for the oil tube. Didn't help. Just for kicks, I pulled out the "breather" from the valve cover to see if it would cause the car to do anything different, and it didn't... idle stayed erratic. is that normal? only thing that changed was a little bit of oil started leaking from around the cam position sensor...
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Old 08-13-2008, 04:33 PM   #13 (permalink)
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well, found an o-ring for the oil tube. Didn't help. Just for kicks, I pulled out the "breather" from the valve cover to see if it would cause the car to do anything different, and it didn't... idle stayed erratic. is that normal? only thing that changed was a little bit of oil started leaking from around the cam position sensor...
..there was a recent thread in the Z3/Z4 forum resembling the problems you are experiencing. just happens that after the owner had his car scanned, it did turn out to be a cam sensor prob.

with or without a Check engine light on, you might want to have yours scanned as well just to see what it is that is causing ur probs
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Old 08-14-2008, 11:27 AM   #14 (permalink)
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well, another day & still no luck tracking down this problem. But I had a couple of observations today:

I can now make the car backfire practically at will through playing with the throttle. As rpm's come down if I put the pedal right to the floor, there is a second delay before a huge wooshing sound with a rather loud POP! & then rpm's come up. Still won't hold rpm's at 1300-1800. you can hear lighter popping in the exhaust in this range.

I had the car running with the air intake off at the MAF & found that if I put my hand over the MAF, the car would stall instantly. I expected this to be normal? Does that mean that the air leak I 'm looking for doesn't necessarily exist?

Still no change in RPM's if I remove the oil filler cap when car is running; which I know isn't right!

I got thinking about other options & thought maybe something's different from the original 92 head & the 94 head I put on. Both are OBD1 & aside from the vanos I didn't see anything really different... except for the cam position sensor. According to realoem they are a different part & and looking at the two heads today, the counterbore that the sensor goes into is alot deeper on the 94. Maybe there's something to this? Could it be possible that the Cam sensor isn't in the right sopt to actually get a proper reading on the cam?

If I get the car scanned would any of these things be disproven?
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Old 08-16-2008, 12:48 PM   #15 (permalink)
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bump!!

Any other suggestions? I'm now to the point that I'm gonna rip the head apart & see if something isn't right with the cams...
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