M42 Fuel issues/ goes from 30 to 0PSI at WOT

[Bimmian89]

PROBLEM FIXED!! SEE LAST POST FOR SOLUTION!



Hello everyone this is my first post to this site. I have searched everything I can and would really like some advice from people who know the M42 motor!

Here is the story I have a 91' 318is. We recently went through pulled the motor, tranny and replaced about everything. It ran amazing for about 8 months, fuel pump went out about 3 months ago I replaced it with OE pump along with filter. Car ran perfect now about a month ago, out of the blue it starts acting up. After the car is warm it will cut out RPMs around 4500 and seems to just run horrible just sputtering out sporadically like its just not getting fuel, which the fuel pump and filter are brand new. Also it starts fine when cold but after its warm and sits for a few minutes it takes about 10-15 turns before it starts, also started out of the blue at the same time as the other problem. Did the stomp test got the bad o2 sensor code 1221. So I got a new o2 sensor, same thing. So we got a new FPR, started it did and drove to get fuel 15 minutes away. It did the same thing. Got the gas and left and it ran perfect smooth pull up to 6300RPM all gears. The next day it does fine. The next day its back to running like crap again. I am absolutely baffled and frustrated to no end. If anyone could lead me in the right direction i would be greatly appreciated! Thanks so much advance guys!

Here is my thread on m42 club, has a few updates and videos. Im stuck right now i have tried everything. New o2 sensor, Coolant sensor is good, TPS is good, Cam and crank sensor are good, spark plug wires all have 5500-6300 OHMS, coil pack are all within the .6-.8 ohms, new spark plugs, new fuel pump.. AFM was rebuilt when motor was done.

http://www.m42club.com/forums/showthread.php?t=17308

[Bimmian89]

http://www.youtube.com/watch?v=AHrhHLXcP38

This is what its doing, does this when cold, warm does not matter.

[roguetoaster]

Even though the AFM was rebuilt I would start my search there, make sure nothing is lodged in the flap area causing intermittent binding, and pop the top to check the track/arm.

Other than that you have a break in a wire somewhere that is causing the intermittent fault. If I had to guess I would say the wire box under the intake is the most likely spot for something to get pinched.

Quite a tricky one you've got there.

[Bimmian89]

Yeah Ill check that stuff out, thanks. If you guys have any clue let me know. I don't know if i mentioned it but the VCG has 5 or so stripped holes so it definitely has a leaking VCG/ possible Vac leak..

[Bimmian89]

Well we did time certs for all the stripped threads on the VCG and did 3 other that were looking shady. Thought that might clear up the problem but it didn't. We tested it after we did that and it ran very good for the 10 minutes we drove it. The. This morning it was back to normal just bogging and cutting out after driving over 10-15 minutes.. Any thoughts or ideas?

[Bimmian89]

Also what's the oil separation process? We took the upper manifold off to get to the holes on top, all cylinder outlets had oil in them. Number 4 actually had tea spoon sized puddle as did 3 just not quite as much the other two had a good amount of residue all over them.

[roguetoaster]

Well we did time certs for all the stripped threads on the VCG and did 3 other that were looking shady. Thought that might clear up the problem but it didn't. We tested it after we did that and it ran very good for the 10 minutes we drove it. The. This morning it was back to normal just bogging and cutting out after driving over 10-15 minutes.. Any thoughts or ideas?

Have you tried unplugging the O2 sensor once it starts to run poorly?

Also what's the oil separation process? We took the upper manifold off to get to the holes on top, all cylinder outlets had oil in them. Number 4 actually had tea spoon sized puddle as did 3 just not quite as much the other two had a good amount of residue all over them.

The oil separator is in the VC and is a plastic system of galleys that the vac out of the forward VC outlet runs through. If you haven't replaced it I would imagine the gasket is probably dead, but that's probably not the big deal ATM.

[Balleristic31]

Also check your tps/wiring to the tps. My wires broke at the sensor on the track and the car ran great except it would randomly hit a wall while accelerating

[Bimmian89]

Have you tried unplugging the O2 sensor once it starts to run poorly?



The oil separator is in the VC and is a plastic system of galleys that the vac out of the forward VC outlet runs through. If you haven't replaced it I would imagine the gasket is probably dead, but that's probably not the big deal ATM.

Yeah, it still runs like hell even though thats the code its throwing 1221 O2 sensor. But im also starting to think its a plugged cat. Took temps with laser gun, inlet side was about 210 and the outlet was around 340-385

[Bimmian89]

Also check your tps/wiring to the tps. My wires broke at the sensor on the track and the car ran great except it would randomly hit a wall while accelerating

This is constant all the time, and the hotter it gets the worse it gets. which makes me think plugged cat. Gonna get it chopped tomorrow and see what happens.

[Bimmian89]

Cat is good. Man oh man this is frustrating.

[Bimmian89]

So I put a fuel pressure gauge on it.. So when i turn the car over its not pumping fuel very fast i have a clear line off the T valve thats on the fuel line, so I can actually see the fuel coming up the line takes about 15-20 cranks for fuel to reach gauge. Will start after that. idles perfect at about 32 psi now when I go to drive it this is what happens. Car at this point is at running temp ~175-180 im in second gear( does not matter does it in all gears, even neutral, psi drops faster with a load on it) cruising at 2K rpms fuel pressure is ~30 the more gas you give it the faster the psi drops until it is at 0 and has no spark you can pump the the pedal and have no response. But if you let off the gas the pressure jumps back up to ~30 psi.. So basically its when you give it gas that the PSI will fall to 0... Any thing I can check? Fuel pump is about 5 months old, same with filter I replaced them at the same time.

http://www.youtube.com/watch?v=MNF7GRzX4f0

Okay I do apologize for the shotty video, my lifeproof case deters sound. As you will see when fuel pressure is at 30 im barley on the gas ( more so momentum than throttle) as you see it drop I am giving it a range from 50-100% throttle, basically the more you give it the faster it drops to 0 and has no spark. Let off throttle goes back up to 30 psi..Thanks for looking!

[oldmann]

Sorry to say, looks like you need another pump. Or you have a clogged fuel pickup or filter.

I have left a fuel pressure guage on my car for 4 months now and I never see less than 35 PSI in any situation. Idle pressure is 42 PSI, after shutdown pump will hold over 30 PSI for 1/2 hour, and won't 0 for another hour or so. Car starts almost instantly, been -5 and starts right up.

Your pump should be under warranty, replace it. The pump I'm running is an Airtex replacement I got from Advance for $63, wasn't the whole unit, Easy install.

[Bimmian89]

Okay thanks! The pump is OEM vdm I want to say, paid like 260 bucks for it. So I'm going to call about the warranty. The pump should not go out in 6 months lol

[monty23psk]

I once had a new Bosch pump for my e28 go out in 3 months. Warranty exchanged and no issues after that.