M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: wenbeaver on October 09, 2011, 11:51:45 PM
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Hi i got a 91 m42 that runs great but under load when you accelerate it pull good but then kinda hesitates then kicks in again! Just wondering if there is any input. Fuel pump?
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Are you getting a check engine light? If so, Google and perform the Motronic stomp test and tell us what codes you're getting. If not it sounds to me like you've probably got a vacuum leak or fuel delivery issue.
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Vacuum leak, or possibly old plug wires/plugs.
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Gret suggestions...I'd check for a sticky AFM flap as well.
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Ok Thanks guys! I dont have a check engine light on an also it seems to do it mostly after its warm! When its cold it doesn't really do it much!
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That sounds like it could a cracked hose somewhere that is being warmed and expanding. Also check to see that your intake boot is fully seated and not cracked around the edges on both sides.
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Have you checked this? It's probably an issue already mentioned but I did this yesterday and it was helping me with my warm start issues:
http://www.m42club.com/forums/showthread.php?t=7757&highlight=figure+out (http://www.m42club.com/forums/showthread.php?t=7757&highlight=figure+out)
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Checked all the hoses all seem good! Checked the wire from the thread an its not plugged in! new fuel pump wasn't that! Not really sure what else to try! :(
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Also if i let up a little bit on the gas it clears up an pulls good then does it again!
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Did you remove the upper half of the intake manifold and check all your ccv/icv hoses?
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Checked all the hoses i could find all seem good replaced a few an still does it! The gas tank has been replaced lately wondering if a fuel vacuum line could be messed up?
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Removed the intake manifold an checked all the hoses under there all seems to be fine. AFM meter seems fine too!?????
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Did you check closely for cracks in the rubber intake boot? It's pretty common for them to split on the AFM end along the ridge where the hose clamp sits. Also check the port and plastic elbow on the bottom. Does it start hard when warm?
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checked all the afm hoses an stuff! Doesn't really start hard when warm either!
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Pull the vacuum line off of your fuel pressure regulator while the car idles. The idle speed should kick up a bit and no fuel should be present in the vacuum line.
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Your FPR is #6.
http://realoem.com/bmw/showparts.do?model=AJ93&mospid=47318&btnr=13_0308&hg=13&fg=15
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When the fuel tank was replaced, did you do any other work? I'm wondering if the hoses are swapped at the tank. The motor can starve for fuel if the supply and return hoses are wrong.
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I tried to hook everything up like it was before i put the new tank in as far as i know. I could have got something screwed up though. Is there a diagram somewhere that shows that stuff? Also i pulled the little hose off the fuel regulator an it didn't seem to make a difference in the idle, also there was no fuel in the line it was just sucking!
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You should've noticed a slight change in idle speed with the vacuum line removed. I would strap a fuel pressure gauge to your wiper arm and go for a drive.
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There are a few diagrams at RealOEM like this one of the tank (http://www.realoem.com/bmw/showparts.do?model=AJ93&mospid=47318&btnr=16_0046&hg=16&fg=05). I don't recall which line is which on the pump. If the lines on top of the fuel tank are the only two you re-connected, swap them around & see if it makes a difference.
Up front at the motor, I think the upper one on the fuel manifold is the feed, the lower one is the return. There is also a vac line there running back to the fuel expansion chamber.
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I had to rehook some of the vacuum lines on top of the tank by the fuel pump but there was only two an they were both different sizes, the gas tank is out of a 325 wondering if that would have anything to do with it? There is a line coming out the lower side by the fuel filter that was not on the old gas tank so i just plugged it!??
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There seems to be gas leaking out of the Activated charcoal filter?? So i took it off today an it rusted on the bottom so i think could be part of the problem?!
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K have done some things an it still does not work! I did the "mess under the intake" way to simplify the vaccum lines an replaced everything! put a new charcoal filter on an it still runs the same, as soon as you run it a little bit it hesitates. I also put other injectors in!?? Makes me think its something with fuel. kinda smells like fuel kinda like its gettin flooded out!
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The bottom of that filter should just be for air, right.
Something's not right here. The six-cyl tank comes in two versions from what I recall. One has a transfer pump that pushes fuel from the left to right, then another pump lifts it out of the tank, finally the main fuel pump pushes it through the filter & off to the rail. The FPR then returns it to the tank.
There's also a vapor system that connects an expansion tank to the purge valve, intake manifold and fuel tank.
I'd take a long look at that tank to be sure its doing the correct thing. You might have a suction problem that's starving the car due to vacuum inside the fuel tank. Maybe try running it with the gas cap off?
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Fuel filter-change it
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Put brand new fuel filter on! I also had tried running it with the gas cap off didn't really seem to make a difference, but i am going to check into that it could easily be creating a suction an starving for fuel!