My car (94 855t) has been really hard to start lately. It cranks, and cranks, and seems to want to fire but won't, like if the timing was slightly off. I've checked, and it isn't. Eventually when it fires, it seems to run fine.

I got a code 336, which Autozone tells me is a crank sensor, though every list of DTCs that I've found online has no #336. I'll take their word for it for now though.

My question is, wouldn't a defective crank sensor affect the way the car ran, not just the way it starts?

 

Well, not really, may want to check the flexplate teeth and see if there in good condition.

 

To update....

I swapped the crank sensor with 2 used ones that I had kept from cars I parted. One came off a running car, the other off a car that had been hit. In both cases, there was no change. Yeah, I know...used parts, but really, what are the odds that I've got 3 bad crank sensors?

So I took the car to a shop and they scanned it. In addition to the 0336 code that I got at Autozone, it also spit out 201, 302, and 1310. I found listings for all of those (all misfire codes), though all I got for 1310 was "TWC damage". Whats a TWC?

Of concern to the tech however was the readings from my O2 sensor. It showed no voltage readings on his scanner. He surmised that it could have been damaged by a blown head gasket that I just replaced a couple weeks ago. However, the codes that he was able to get are very intermittent. Sometimes the car will start right up, and other times not at all. When it does start, it runs fine. He suggested that it may be computer related.

So my question I guess is, how common are computer issues in the 850? I've had Mitsubishis that were notorious for bad computers, but I've not heard much about Volvo computers being bad.

Any thoughts appreciated. Just throwing money at multiple parts, hoping one of them fixes the problem, is not my idea of fun.

 

TWC codes are for the catalytic converter.

 

I would take a look at your cap, rotor, wires and plugs. How old are all of them?

 

Could be Cam position sensor also? Not sure.
I have a spare ECU I would let it go for $50 + shipping.

 

All replaced when I did the head gasket, within the last month.

I pulled both computers out of my other '94, but it turns out I burned up my starter cranking it so much to get it running. I should be able to get to it this weekend.

 

For the benefit of the next person doing a search, the solution is...(drum roll please)....

I pulled both computers, and installed the ones from my other car, and this one started right up. No codes and no problems, but also no clue how my computer went bad. The car runs great, just as it did with the bad computer, so obviously it was just a relatively minor circuit that affected starting.

Anyway, thanks for the input, and good luck to whoever is reading this in the future.