'97 540 - Misfire issue
'97 540i, auto, 183,000 km, all stock. I've owned it about 5 years and put about 90,000 km on it. Never had any engine issues.
Car has started showing fault codes for misfires....random, and cylinders 5, 6, & 8
The CEL will only come on if I use full throttle on the car. If I clear the code and drive the car gently there are no problems.
Checked and changed the plugs (they had approx. 100,000 km on them). Two plugs were somewhat loose in the block, and two had the coil connector submerged in oil (looks like a valve cover leak). Plugs were pretty clean otherwise.
The other day I used full throttle and when the revs exceeded approx. 4000 rpm the CEL started flashing and the engine started cutting out. Letting off the gas, the CEL went solid and the car felt like it was firing on 7 cylinders. Rough idle, and from a stop if I took my foot off the brake the car would sort of lurch forward and stutter. At higher rpm the engine would smooth out.
Turned the car off for a while and cleared the codes. Car runs fine now, but no full throtlle blasts for the time being.
Coils look like they are original. Fuel filter has about 90,000 km on it.
Where to start? Swap coils around? Any way to test the coils?
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