There might be a lesson here for others, although I'm sure it's been stated enough times that I should have already known better - I'll try to get to the point soon.

A couple of months ago I bought a nice looking 93 944 with 170k that had passed the safety test but failed on smog testing. I bought it for $1650 figuring with little rust, no oil leaks, a new exhaust front to back and almost new tires and snows, I could figure out what the problem was and throw a couple hundred $ of parts into it and have a pretty good car. A short test drive revealed that it started well, idled OK, and had a kick-down cable that needed adjusting. It was pouring rain, so I was a little distracted. On the drive home I found it seemed to miss a little in the 2000rpm range especially on partial deceleration.

I did a standard tune-up since plugs looked a little old and sooty and the distributor rotor was pitted and worn. I put in new plugs, wires, cap, rotor, air filter, changed the oil, cleaned the flame trap and filled the tank with premium. Car seemed to run a little smoother but still had the hesitation at low throttle and seemed to miss a bit if reved to 2000rpms and held. E-test failed on CO,HC and NOx at 25mph and passed at idle, numbers pretty much unchanged from the previous owner's.

Over the next month or so I tested and retested and swapped in new and used parts trying to get at the problem: FPR, air temp sensor, engine temp sensor, knock sensor, radio suppression relay, replaced the CPS due to a frayed wire, coil/power stage, MAP sensor and TPS. I removed and refreshed every ground I could find. Car is still starting fine and getting reasonable gas mileage, has good acceleration. E-test failure, same numbers.

Now I'm looking seriously at the idea of a vacuum leak mimicking an electrical issue, but I can't hear or see one, can't get the idle to change with propane or carb cleaner, but I keep going - change all the vacuum hoses, change the intake manifold gasket, change injector seals (I'm thinking it must be a very small leak that is allowing the engine to run OK but not just right.

I'm running out of options here, so I replace a perfectly good O2 sensor even though my multimeter tests say it's OK - must be flaky I think - no change.

Finally, I give up and take it to my local independant Volvo guy - he spends a couple of hours and doesn't solve it, I need the car back, but he does say it is not a vacuum leak and there seems to be some spark disfunction, maybe a bad coil. I tell him I've already changed the coil with a used one and it made no difference. He agrees it would be pretty unusual for both coils to exhibit the same symptoms and says he'll think about it. I post here asking about Regina coil failures and Lucid posts back with some reference to grounding of the coil. I realize that I assumed the ground for the coil was to the body right where it is mounted, I follow the black wire along the body to a graound that I missed completely by the headlight - I even looked for this one a couple of times - it was buied under the harness and guess what - corroded like crazy. 10mm socket and some sandpaper and it looks like all my symptoms are gone. So wadda ya think o that!

Ron
93 245
93 944