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Old 06-22-2019, 05:54 PM   #1
E30Rott
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It has been some time! Banging my head over this issue.

Hello all,

Its been a long time!
Can't believe e30tech is gone!
I was quite active over there in the past... sad to see it gone, maybe a few old timers will remember me from there

So after 2 weeks now of forum searching and diagnosing I'm here to see what the collective mind has to offer on my problem.

Bought a 1987 325is a few months ago with a dead clutch slave, so I was never able to drive it.

The car starts up without issue, idles evenly, no issues there cold or hot.

When the car is under load and giving anymore than maybe 25% throttle starting around 2k rpm to 3k rpm the engine is not happy.

Car misses badly, occasionally bucks, etc.

Once you get past this rough spot, the car pulls to redline very strong.


If at a standstill in neutral/clutch-in the car will rev to redline 4 out of 5 times without a hiccup. Occasionally if really pressing into the pedal around 2k - 3k as similar to above I can feel/hear it break up a bit then clean back up and rev cleanly to redline.

I've replaced or verified that the AFM, CTS, TPS, CPS, o2, Coil, Plugs + Wires, Cap + Rotor, Intake boot, alternator, grounds and vacuum lines are all functional per the Bentley.

DME in the car has the tell tale yellow paint of being from a wrecking yard, not sure if that is of any concern, but I'm putting it here to help get ideas.

It would appear the PO was trying to figure this out as well as all fuel lines in the engine bay are new, and a binder full of receipts for various parts listed above.

Jumping the fuel pump relay I get a very audible under car pump running, and a only minor audible from the inside pump (with cover off of it, nothing to block sound) but to the touch I can feel it running.

Car has a 153 DME, so I cannot stomp test.
I'll have to check again, but I believe the last time after driving, the next start up the CEL flashed twice indicating o2 sensor issues, but the o2 is new, and tests out correctly per Bentley.

I'm thinking next step is to confirm fuel pressure at the rail, and check to see what spark plugs the PO installed, in case this could be an issue of not using copper plugs? Also looking into buying a smoke tester, as I've checked all the known vacuum leak spots.

Also when pulling the cover off of the fuel pump area, I noticed one oddly cleaner line that appears to be kinked, from what I can tell on ETK this goes to the expansion tank? Can anyone confirm? Link to pictures : https://imgur.com/a/C2DS7JW

Last edited by E30Rott; 06-30-2019 at 12:52 PM.
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Old 06-23-2019, 03:34 AM   #2
E30Rott
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After more reading I see that the Bentley's listed spec of 960 +/- for the CPS is incorrect.

It appears that the correct spec is 540 +/-

I have a reading of 890 ohms, so I will replace the CPS and see if that solves it.

AND I'm guessing this is the problem...
Guess I will look over the rest of the PO's installs and be sure he didn't half ass the fuel lines in a way they can rub :0



edit: Oddly enough that didn't solve the issue.
Going to look into fuel pumps, injectors next.
Any other ideas?

Last edited by E30Rott; 06-25-2019 at 09:44 PM.
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Old 06-24-2019, 08:41 AM   #3
doctorx
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i had this recently... turned out the fuel pumps were bad. The tank was full of rust and the ground wire on the in tank pump was missing. It was completing the circuit with the gas! When I first got the car, the tank was full, but as fuel burned off, i started getting a stumble around 3-4k... then it got to the point it would not pull itself. It sounds like you have the same issue.
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Old 06-24-2019, 06:08 PM   #4
E30Rott
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Quote:
Originally Posted by doctorx View Post
i had this recently... turned out the fuel pumps were bad. The tank was full of rust and the ground wire on the in tank pump was missing. It was completing the circuit with the gas! When I first got the car, the tank was full, but as fuel burned off, i started getting a stumble around 3-4k... then it got to the point it would not pull itself. It sounds like you have the same issue.
I've drained the tank, and she only has maybe 2 fresh gallons on 93 in her.
That said, the fuel pumps are about the last items that have not been replaced on this car as far as fuel/air/spark is concerned. Aside the injectors... so...

I've ordered 6 new injectors, and a fuel pressure testing setup.

Amusingly I've got a nagging feeling this is all going to be some vacuum leak I haven't located.
So I'll probably end up ordering a smoke testing rig as well if the fuel pressure is on spec.

Thank you for sharing your experience, I'll double check the ground at the pump to be sure it isn't doing as you've described.
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Old 06-27-2019, 01:36 PM   #5
AndrewBird
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What about the fuel filter? Perhaps it's clogged full of junk.
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Old 06-29-2019, 06:39 AM   #6
packratbimmer
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Read up on reading exhaust temperatures before and after the cat. Sometimes when a car has not run right in a while, the cat gets somewhat clogged.
As a last resort, I ran a "cat clean" product through my car (89 325i) and it gave quick results and gradually the car improved more as I drove it. I got as high as 28 MPG on my last road trip (it had been in the low 20s for a few years). I had not changed anything else so I'm thinking there must be something there...
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Old 06-29-2019, 06:37 PM   #7
E30Rott
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Quote:
Originally Posted by AndrewBird View Post
What about the fuel filter? Perhaps it's clogged full of junk.
I did also replace the fuel filter, though the one there was relatively new.
No dice there.
I'm still not sure its going to be a fuel issue, as once you break past the ~3k range it'll pull like a train to redline.
Basically to drive it around I've been driving it like I stole it

Quote:
Originally Posted by packratbimmer View Post
Read up on reading exhaust temperatures before and after the cat. Sometimes when a car has not run right in a while, the cat gets somewhat clogged.
As a last resort, I ran a "cat clean" product through my car (89 325i) and it gave quick results and gradually the car improved more as I drove it. I got as high as 28 MPG on my last road trip (it had been in the low 20s for a few years). I had not changed anything else so I'm thinking there must be something there...
From what I have seen under the car, they have replaced the exhaust from the collectors to the muffler with 2.5" that said there is a "tall boy" beer sized (what I thought was a resonator) near the guibo area. Perhaps that is a tiny cat.

It did smoke like crazy the first day I got it registered and I drove it around town.

Thanks for the idea, I'll look into what may be a cat.
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Old 06-30-2019, 03:25 PM   #8
jstoll
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do you have a digital multimeter? I would start looking at sensor outputs while the problem occurrs including the fuel pressure check the o2 sensor while the problem happens.. you can see if its leaning out of getting rich... sweep the tps and see that the values change as they should smoothly ... check the output from the airflow meter...check your grounds ...try to perform the checks while the problem happens not at idle and non loaded ...
it sounds like a flakey crank sensor... is the crank pulley wobbly? is the gap correct and consistent?? can you borrow a lab scope and check the waveform on the crank sensor? see if it breaks up when the problem occurrs?
take care
JAK
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Old 07-02-2019, 04:51 PM   #9
packratbimmer
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Not sure if this will help, but my car would not start yesterday after I took it out. I had a fuel pump relay with me and tried it. Fired right up. Second time on my 325i cars.
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