Engine Speed Cycling Under Load

[ChaCha]

I have a 95 325i Convertible with 89,000 miles. The car drives fine except when under load the engine speed cycles up and down. For example, on a flat road at constant speed, say 60 mph, all is normal. If I try to accelerate slowly to 70 mph the engine speed will constantly speed up and slow down about 1000 rpm. If I accelerate with full throttle this does not happen. Any chance there is a simple fix to this type of problem

[O.J.]

Hi,

I had a very similar problem on a K reg 320i Coupe a year or so back. I had a diagnostic machine flag up a fault with th O2/Lambda sensor. Unfortunately I never had replaced so can't tell you if it was the problem or not. I have come to understand the cam sensor can also give similar problems & would suspect if this was the case it would have a greater effect on your engine one as it is fitted with VANOS (my old 320 wasn't). I would guess these two culprits are most likely & while a diagnostic machine can help most of the time it has been known for different "unmonitored" faults to flag up as something else further down the line by a sensor.This is why I never replaced my O2/Lambda sensor, if I had kept the vehicle I would have had someone look at it with a bit of, hopefully BMW, experience who may know of a common simple fault such as an air leak etc. I've got a BMW magazine here somewhere (!) which costs up & describes an E36 cam-sensor change using both new & S/H parts & I seem to remember some strong advice to stick to genuine BMW parts as some aftermarket ones give trouble. As soon as I find it I will give you the details. I have a feeling the O2/Lambda sensor was quite expensive at around £80 plus fitting but this might be a mile off as it was quite a long time ago. I'll look into this also..

Best Wishes, O.J.