I've got a 1988 BMW 325is. It's turbocharged with stock management (RRFPR, TCD chip, 30lb injectors, adjusted AFM).
My problem is an occasional hiccup. Randomly, when on the throttle (partial or full) it will get a slight hiccup or miss, but rev strong after that. Just a slight hesitation. Doesn't seem to happen at any specific RPM or boost pressure that I can tell. Looking at the AFR gauge when this happens, you will see a quick rich condition.
AFRS look like this: 12.7 ... 12.8 ... *boom hiccup* 9.9 ... 10.5 ... 12.7
Also, occasionally (4 times total now) it will have a complete shutdown. I'm talking bucking, freaking out, RPM gauge goes funny, car dies and I have to pull off the road. Once I waited a minute and the car restarted fine. The other 3 times I've had to disconnect and reconnect the battery to get the car to crank over.
Sometimes, but not always. it seems that this is related to bumps on the road. On a trip back from the racetrack it seemed that it would hiccup whenever I went over the little raised lanemarkers on the road. When I had to go onto the bumpy grated stuff on the side of the road to avoid a road obstacle, the car bucked and shut down.
These freak outs seem to only happen after long periods of driving (40+ minutes). The hesitations also seem to increase with time driven. Sometimes I can make entire trips without a single hesitation.
Related things I've done in the last year:
Cap
Rotor
Distributor
Spark plugs
Fuel filter
Fuel pump
Cleaned battery connections
Cleaned battery ground
Cleaned engine ground (oil-pan to chassis)
Any ideas of what else to check?
My problem is an occasional hiccup. Randomly, when on the throttle (partial or full) it will get a slight hiccup or miss, but rev strong after that. Just a slight hesitation. Doesn't seem to happen at any specific RPM or boost pressure that I can tell. Looking at the AFR gauge when this happens, you will see a quick rich condition.
AFRS look like this: 12.7 ... 12.8 ... *boom hiccup* 9.9 ... 10.5 ... 12.7
Also, occasionally (4 times total now) it will have a complete shutdown. I'm talking bucking, freaking out, RPM gauge goes funny, car dies and I have to pull off the road. Once I waited a minute and the car restarted fine. The other 3 times I've had to disconnect and reconnect the battery to get the car to crank over.
Sometimes, but not always. it seems that this is related to bumps on the road. On a trip back from the racetrack it seemed that it would hiccup whenever I went over the little raised lanemarkers on the road. When I had to go onto the bumpy grated stuff on the side of the road to avoid a road obstacle, the car bucked and shut down.
These freak outs seem to only happen after long periods of driving (40+ minutes). The hesitations also seem to increase with time driven. Sometimes I can make entire trips without a single hesitation.
Related things I've done in the last year:
Cap
Rotor
Distributor
Spark plugs
Fuel filter
Fuel pump
Cleaned battery connections
Cleaned battery ground
Cleaned engine ground (oil-pan to chassis)
Any ideas of what else to check?
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