Volvo Repair: Volvo 240 hesitation, fuel pump relay, 4 ohms

Question
Hello Roger,
I have a 1989 240 SW. A weeks ago it statred hesitating when I would accelerate, that is press the pedal about half way down. When I let the pedal back up to a certain point, it will sort of go back to normal. I checked the computer codes and I got trouble codes for a missing speed signal,a bad signal from the air mass meter and also O2 sensor. I know these need adressed, but when I used a multi testor on the AMM, it tested at about 4 ohms, which was normal. I dont know much about the speed sensor, as my manula does not have any info on it. I also checked my fuses and there is no corrosion. I also checked the fuel pump relay, and it seems to be ok, but im not too sure. My old 240 did the same hesitation thing and I replaced the main fuel pump and it was fine after that. Would that be the culprit or do my myriad of trouble codes have any effect. Oh, by the way, it only seems to hesitate on moist, misty, rainy days. Im usually not bad at diagnosis, but there are too many variables for me in this situation and I dont want to waste money on not needed parts if I can avoid it right now. Hope the description can help and not confuse you. Any help would be great. Thanks again,

Adam

Answer
Adam, even though 4 ohms is normal, the AMM is avery picky piece.  The speed sensor is most likely the culprit and cheapest of the pieces.   Its on the bell housing and if its original, then its time to replace.  If it goes bad then the car wont run at all.  Fuel pump relay if its original, then replace that as well.  Roger