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1988 325is idle issues! HELP!

4K views 19 replies 6 participants last post by  chinonca 
#1 ·
It seems like after a long drive if I stop and go into a store and then restart it the engine struggles to stay running. It starts no problems but goes "vroom" (then rpm goes down like engine cuts off from gas) then "vroom" and repeats that until it shuts off. And if I apply the gas sometimes it will rev up and sometimes it sounds like it will shut off. After a few minutes of reving and restarting it idles fine and drives like nothing was ever wrong! I did just replace the fuel pump but i dont see how that could be the problem. Can someone try and help me narrow it down to what the problem is?????:eek:hnoes:help
 
#3 ·
One part for that then; MAF, thats what I would go for, easy DIY but do get one from BMW a little more cost, less heartahe later.
 
#6 ·
.... MAF doesn't appy to your car... you have a AFM (Air Flow Meter...)
Hows your MPG?
HowsDoes the car feel when it is warmed up?

It could be Leaky injectors Cold start injector or the tempature Sensor...
 
#7 ·
after it goes through the erratic idle for a few minutes or so, it idles and runs like nothing ever happened. I took off the intake housing and cleaned off the Air Flow Sensor even though it looked clean. while it was off (both air filter and Air Flow Sensor) i started my car and it ran exactly the same as it would with the filter and sensor plugged in. so im thinking it could be the sensor.

And i wouldn't even know how to check the injectors, cold start injector, or the temperature sensor to see if they are fine:conf
 
#9 ·
Since this happens after a long drive (hot), I might suggest that you may be experiencing vapor lock in the fuel lines... especially if you just replaced the fuel pump... the new pump may have a bad check valve allowing the fuel pressure that should be built up in the injector rail to bleed back to the tank. If that happens and it is hot under the hood you will have a pressurized gas inside the fuel lines and it will be difficult for the liquid gasoline to get back up to the injectors. Has it been a little long cranking when it's cold as well? If so, next time you go to start it cold, turn the ignition on and of about 3 or 4 times and see if it starts up real quick that time. That will run the fuel pump prime sequence several times and re pressurize the fuel system that had previously bled off, if that is the cause. The other issue could be the fuel pressure regulator. You can test it fairly easily by pulling the vacuum line on and off of it while its idleing. You must put your finger over the vacuum line immediately upon removing it or it will cause the motor to stumble. If removing the vacuum from the FPR has no effect on the engine, you could use a new one.

Good luck... I hope the IAC valve was the issue.
 
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