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Old 01-24-2018, 11:19 AM   #1
jhaurimn
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Low on Power (obd1 m52)

Heres specs on the setup

89 325i
Obd1 m52
m50 intake
trm tune chip
413 red label ecu

Starting this winter, my car started having power issues and on seemingly random occasions, the car would lose all power while driving and would buck back and forth for a few moments before it would return power back. (very sketchy if you ask me)

Here's what i've done so far:

-Cleaned icv
-Inspected/replaced intake hoses to and from icv
-Cleaned tb
-New spark plugs
-New fuel pump (inside of fuel tank looked spotless, no signs of rust)
-Cleaned/replaced maf with known working part
-New, dry cone air filter
-New tps (tested resistance to confirm part is good)
-New fuel filter
-Lucas injector cleaner when filling up car
-New cam position sensor
-New coolant temp sensor (tested resistance to confirm part is good)
-Cleaned engine main ground
-Replaced cpu
-New fuel pump relay
-New main relay
-Refurbished injectors
-New fpr and vacuum hose from fpr to manifold
-New tb gasket
-Tried another icv, no change
-Inspected coils/coil boots/plugs, nothing out of the ordinary
-Swapped coils for different set
-New coil boots
-Vacuum gauge test to confirm no exhaust restriction


I'm starting to run out of ideas. The car idles smoothly (although I have noticed once the car warms up it does idle a little high, around 1k rpm) but the car is definitely low on power compared to before. It feels like it has flat spots in the acceleration and then occasionally will fall on its face and start that bucking symptom.

Has anyone run into this issue before?
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Last edited by jhaurimn; 04-13-2018 at 03:04 PM.
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Old 01-24-2018, 02:28 PM   #2
MR E30 325is
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I had this exact issue with my 97 M3.

Mine was the MAF, which you have already ruled out. I did the same checks as you.

Check and clean grounds??
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Old 01-24-2018, 04:40 PM   #3
jhaurimn
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Originally Posted by MR E30 325is View Post
I had this exact issue with my 97 M3.

Mine was the MAF, which you have already ruled out. I did the same checks as you.

Check and clean grounds??
Definitely ruled out the maf. Had bucking issue, replaced maf and on the test drive it kept doing it. (this is what blunt suggested to me too)

Im an idiot with wiring, so bear with me. Is there a way to check if everything is grounded properly without un-doing wiring and sanding the contacts?

Also I know of the ground that goes from the engine to the frame/motor mount, which other ones should i inspect?



Also worth noting that I replaced the fuel filter today with no difference, then i also installed the stock chip back into the ecu to see if that would change anything. No dice. Going to try and get another 413 red label to swap out to make sure its not that.
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Old 01-25-2018, 07:09 AM   #4
MR E30 325is
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Quote:
Originally Posted by jhaurimn View Post
Definitely ruled out the maf. Had bucking issue, replaced maf and on the test drive it kept doing it. (this is what blunt suggested to me too)

Im an idiot with wiring, so bear with me. Is there a way to check if everything is grounded properly without un-doing wiring and sanding the contacts?

Also I know of the ground that goes from the engine to the frame/motor mount, which other ones should i inspect?

Also worth noting that I replaced the fuel filter today with no difference, then i also installed the stock chip back into the ecu to see if that would change anything. No dice. Going to try and get another 413 red label to swap out to make sure its not that.
You can check using a voltmeter, but I would pull em off and sand em just to be sure. I personally prefer a visual inspection to check for cracked wire covers, etc that may short out while you're driving.

There is the main ground, there is also the ground at the fuel rail to one of the engine hoist bracket bolts, and the DME should also be grounded.

Haha I did the fuel filter too, also to no avail. The problem plagued me for over a year. Towards the end I gave no shits, and dove in head first trying to figure it out.

Good luck.
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Old 01-31-2018, 03:03 PM   #5
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New cam position sensor and new coolant temp sensor installed and cleaned the main engine ground contact points. car felt pretty good on test drive. Then drove the car today and the power was very low again.

Im running out of ideas :/
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Old 02-07-2018, 01:04 PM   #6
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Well, replaced the ecu today with no change at all.

Looking to replace the main and fuel pump relays next.

Now im REALLY running out of ideas.

Worth noting that when i have power loss or bucking issues, the car will rev just fine in neutral. Only when under load am I having these issues.
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Old 02-09-2018, 05:47 AM   #7
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New main relay, fuel pump relay, refurb'd injectors, new fpr, replaced vacuum hose from fpr to manifold. Still low on power.

:/
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Old 02-13-2018, 09:25 PM   #8
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After driving with new injectors/fpr, car seems to have a smoother delivery of power. However, the torque at high rpm range is definitely suffering.

Anyone have an idea as to why power would suffer on the high end? Everything seems normal under 4k rpm for the most part.
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Old 02-15-2018, 07:23 AM   #9
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Vanos issues perhaps? I'd try applying power to the solenoid and see if it moves. If you've never replaced the seals on the vanos piston, they are probably worn out and are leaking, causing the vanos to not engage properly.
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Old 02-15-2018, 07:37 AM   #10
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Vanos issues perhaps? I'd try applying power to the solenoid and see if it moves. If you've never replaced the seals on the vanos piston, they are probably worn out and are leaking, causing the vanos to not engage properly.
Would you apply power to it with the solenoid removed? I don't see how you could tell it was moving or not while installed still.
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Old 02-15-2018, 10:10 PM   #11
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You can apply power to it with it installed and should feel it click. Otherwise, pull it and check it with it out.
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Old 02-16-2018, 01:03 PM   #12
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Vanos issues perhaps? I'd try applying power to the solenoid and see if it moves. If you've never replaced the seals on the vanos piston, they are probably worn out and are leaking, causing the vanos to not engage properly.
This was a sudden power loss, and the vanos handles torque in low rpm. My car is low on power mainly in the higher rpms and also falls on its face randomly. No rattling from the vanos either. Don't think it would cause this.

I am setting up a fuel pressure gauge once it warms up, despite having replaced the fuel pump, filter, pressure regulator, injectors, and the fuel pump relay. If that all looks normal, I am going to back-pressure test the exhaust.
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Old 02-21-2018, 05:59 AM   #13
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Noticed this morning that the return fuel line attached to the fuel rail leaked a bit on cold start this morning, but sorted itself after running for about 30s.

Not sure what could of caused this....I think i am going to swap back to my old injectors.

Edit: Changed back to old injectors, also noticed a small cut in the fuel line. All is corrected but still desperately low on power.
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Old 02-22-2018, 01:29 PM   #14
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The vanos engages not much off of idle and stays on until higher rpm. If it doesn't turn on, you will have a loss in power. Rattle has nothing to do with function, and if anything, no rattle would indicate that it isn't turning on as unless it has been updated with late model parts, it will rattle.
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Old 02-22-2018, 05:43 PM   #15
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You know, on really cold days i used to hear a rattle from the vanos for 2 seconds on cold starts before going away, and its been very cold and I havent heard the rattle in awhile...

Would that indicate that possibly my solenoid went bad? Probably worth swapping that out before going after the vanos seals. I did the vanos seals on a m54, but single vanos looks like a pita in comparison.
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