Hey guys, I have a 1987 325e and when i accelerate past about 1/4 throttle in any gear, except first, the engine bogs down and wont accelerate. I have a new AFM in and just checked the fuel pressure which was normal at around 36 at idle. Any other ideas on what it could be? Thanks
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Bad spark plugs or a weak spark are the easy to fix culprits.
Your car should have two fuel pumps, one in the tank and another in front of the driver rear tire. The in tank pump is low pressure, to lift fuel out of the tank and supply it to the external pump, which provides high pressure to the fuel rail. At idle, the high pressure pump can 'suck' enough fuel up from the tank to supply adequate pressure, but as the load increases, the pump is no longer able to suck up enough fuel AND provide pressure to the fuel rail. Under sustained load, the fuel pressure will drop off.
Is it a smooth idle? Are there any vacuum leaks? Does the temp sensor test good?
If you don't have a Bentley manual, I highly recommend you get one, and start checking the fuel delivery system in accordance with the tests in the manual. You can quickly rule out almost all problems with a fuel pressure sensor, a volt meter, and the Bentley manual in a few hours.
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