I had a rough idel problem (91 740) that was easily fixed by replacing the knock sensor. This also boosted my mpg by about 20%. I must add that my check engine light had come on which suggested the knock sensor be replaced.

My check engine light had been illuminated so I checked the codes and a faulty knock sensor was reported. I cleared the codes, waited a while, and sure enough the same code reappeared. So, it looks like there might be a problem here. My plan of attack is to first check/clean the connection then repl...

I had a very similar problem with my 740 wagon. My problem ended up being a faulty relay (I can't remember exactly what the relay was but it had something to do with the fuel system). I dried off my plugs, changed my oil (due to the gas in the oil), swapped out the relay and was good to go.

On my way into work this morning, my speedometer seemed to be a bit jumpy. Accelerating, deccelerating and driving at constant speed the needle with "flicker" up occasionaly. Any ideas on what is causing this. I have never seen it before. BTW 91 740 wagon. Thanks.

Diagnostics Complete!! The directions were great. Turns out the fault was a faulty message (or lack thereof) from the knock sensor. I am going to wait and see if the fault occurs again, and then go from there to figure out the problem. Thanks.