Low on Power (obd1 m52)

[2mAn]

I think its the coils. They simply have a shelf life and most swaps are on the original 20-25 year old coils. OBD1 should have 2 grounds in the middle of all the coils too grounded to the valve cover. The coils are usually date stamped. Its not cheap, but that was the only thing that gave me a problem with the OBD1 M52 motor

[jhaurimn]

Pretty sure I can rule out icv and coils. I tried a used icv and got same results. Also inspected/cleaned all the coils and coil boots, everything looked good there as well. I took two short videos of a symptom ive been having that might help indicate the problem.

Basically when I drop out of gear, the rpms sort of "fall" from 2k-1.2k, and it bounces back up. If i am rolling to a stop while in neutral, the rpms will stay around 1.4k until I come to a complete stop, then it will eventually drop back down to 1.2k.

Id also like to mention my car idles at a proper level when cold, but after warming up a bit the idle increases.

https://flic.kr/p/23L7vqT

https://flic.kr/p/258aG54

[jhaurimn]

Car hasnt done this in awhile, but it fell on its face today again.

Car loses all power/ability to accelerate until i mash the gas pedal for a few seconds, then it comes back to life.

I am also averaging 14mpg... way less than i was getting before winter.

Other symptoms include a very slightly stumbly idle, and my idle has also been pretty high, around 1250k. Ive also noticed the rpms bounce a bit when shifting into neutral and coming to a stop, basically how the car acts when a reset ecu.

A few things Im thinking it could possibly be:

Bad o2 sensor - I already replaced it with a bosch o2 within the last year)
Bad icv
Bad coil - Although I dont think one bad coil would cause my car to lose all power
Restricted exhaust - it seems like exhaust gases pass through out the muffler just fine, so perhaps a partial restriction?
Bad maf - car acted exactly the same when i swapped mafs and the idle drops low and the car stumbles when i unplug it. i suppose there is a chance my spare maf is also bad?
Bad crankshaft sensor - ive heard of this sensor causing start issues but not power issues

I can understand the vanos giving the bad mpg symptom, but theres no way it would cause the car to lose all its power intermittently.... right?

This is driving me insane :(

[jhaurimn]

https://www.amazon.com/dp/B010O1FBLC..._n-gMAbGYM9SXS

That's the adapter to use to test. Bolt this in place of the oil line and hook an are compressor up to it. Then manually apply power to the solenoid to activate the Vanos. You have to take the valve cover off to be able to see if it is engaging.

If your seals haven't been replaced, they are bad. The original seals went bad on less than 50,000 miles. The fix is replacing it with a viton o-ring instead of the stock buna-n. It's an easy fix. New seals are cheap too.

I did vanos seals on my old e46 m54, it was definitely straight forward. Seems like single vanos is a little more tricky. they talk about locking the crankshaft through the bellhousing or something like that, but im using the m20 transmission, not sure how to work around that.

Ive definitely thought about buying a spare set of obd1 coils, might have to do that just to eliminate the possibility.

[mr.vang]

My e36 m3 was having random top end power issue. I found a set of new bav auto coil packs at the junk yard from an e46 and replaced it witm my old one. That fixed the problem for me. The car pulled much smoother, faster all the way to redline with the new coil packs.

[AndrewBird]

https://www.amazon.com/dp/B010O1FBLC..._n-gMAbGYM9SXS

That's the adapter to use to test. Bolt this in place of the oil line and hook an are compressor up to it. Then manually apply power to the solenoid to activate the Vanos. You have to take the valve cover off to be able to see if it is engaging.

If your seals haven't been replaced, they are bad. The original seals went bad on less than 50,000 miles. The fix is replacing it with a viton o-ring instead of the stock buna-n. It's an easy fix. New seals are cheap too.

[jhaurimn]

Thanks. I already replaced the solenoid with a one on ebay that was cheap enough i figured id give it a shot. Realized the solenoid in my car did not appear to be oem and had a much shorter cable than the one I bought from ebay.

So heres an update:

The URO fuel pump i installed about a month ago began buzzing very loudy. Since I was pretty certain the fuel pump wasnt the cause of my power issues, I installed the bmw pump back into the car. No more buzzing, and let this be a lesson to everyone else. If you are considering cheaping out on the fuel pump and getting a uro...just dont.

I have to say, the car has been behaving MUCH better the past few days since I installed the new solenoid, put the old fuel pump back in, and changed the oil. However it has also been a lot warmer outside, so I think this has something to do with it.

I do still get occasional hiccups and sluggish-ness, and my idle doesnt seem quite as smooth as it was before. I cleaned the icv but I think I am going to try and replace the part with a spare I have sitting around.

I was planning on testing fuel pressure a week ago, but because of the fuel hardline setup I have under the intake mani, I needed more spare fuel hose. (sure wish i had the obd2 fuel rail right about now :) ) I picked some up at autozone the other day so I plan to revisit that just so I can completely rule out fuel pressure being the issue.

Still need to test exhaust back-pressure as well.

Do you have any info on the air line adapter for checking the vanos? Would that tell me if my seals were bad?

[AndrewBird]

You only need the air line adapter to test the entire vanos system. To test the solenoid, just unscrew it from the housing and apply power to the connector and see if it moves. If it doesn't, it's bad.

[jhaurimn]

Test the solenoid out before you replace it. It's easy to do and will tell you if it's bad or not.

Cold start up rattle is usually lifters before they fill with oil or timing chain noise before the tensioners fill. Vanos rattle is at a certain RPM.

Whats the best way to go about that? From what ive researched, you need to have some sort of air pressure tool to properly test it.

[AndrewBird]

Test the solenoid out before you replace it. It's easy to do and will tell you if it's bad or not.

Cold start up rattle is usually lifters before they fill with oil or timing chain noise before the tensioners fill. Vanos rattle is at a certain RPM.

[jhaurimn]

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.

[AndrewBird]

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.

[jhaurimn]

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.

[jhaurimn]

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.

[AndrewBird]

You can apply power to it with it installed and should feel it click. Otherwise, pull it and check it with it out.