Hello,
I have a 1993 Volvo 940 with 278,000 miles. Recently I have had an issue with a misfire and then my car stalling out. My car use to only have a misfire when it rained or when it was wet. It would misfire then I would drive it for a few miles then it would go away. I started noticing the misfire more and more frequently. Last week my car had the misfire again (in the rain) and then suddenly I had no power, my foot was on the gas and I couldn't move. Then the cared just died. I couldn't get it to start again so I had it towed. My mechanic did a compression check (came back fine) and replaced the ignition wire (I think that's the right term - I had it replaced 2 years ago). I drove it 2 times and it still seemed off and it was misfiring. The second time I drove it, it had rained the night before. I started the car and it didn't start as quick as it normally did (I had to hold the key a little longer) and it had a misfire. It cleared up and I stopped at a light. I had very little power and it felt like it was getting ready to stall out. I lost more power going up a hill at 10mph finally it stalled out. I had it towed to the mechanic again and he sprayed water under the hood and couldn't get the car to stall out again. He recommend replacing the fuel pump relay. I did that and have driven it a little. It seems like the car is driving better then before, but it hasn't rained since I replaced the piece. Would it make sense to be the fuel pump relay?? I'm really nervous about driving more then a couple of miles. Any suggestions?
Thank you!
Annelise

 

First thing I would change would be spark plugs, plug wires, distributor cap, and rotor

 

I replaced all of those about a year to two years ago. My mechanic checked them and said they were all fine.

I forgot to mention in the original post that the fuel pump relay is from January 1993 -never been replaced.

 

If compression was good...
You may need a tune up, a good start for your symptoms...

If that doesn't solve it
I'd look at the Crankshaft Position Sensor, clean the throttle body, run some fuel injector cleaner through the system.

Is it a Bosch ignition system? If so, the MAFS could be acting up... Fuel relay? No...
Just some basic TLC maintenance stuff... It may sound overwhelming but it's really not.

 

Thanks! I'll try it!

 

this 'misfire', what exactly do you mean, like it stutters and loses power, or does it backfire and cough ?

 

Just something... whenever I've had rain related problems, it's generally been due to bad grounding. You may consider looking at where all your electrical components ground and ensure that they grounding solidly. This may not solve anything... but I generally try to eliminate grounding issues before I try to replace parts... 'cause if it is that, it is an easy fix... Also, there may be some combination of issues leading to this, and this may eliminate one.

 

Yes it stutters and recently started losing power. It has been really nice here this week and the car has been perfectly fine! No problems. But it rained last night and I tried to drive the car this morning and it did the misfire or stutter thing again. Today I didn't lose power but I also only drove around my parking lot. It does not backfire though just stutters.

 

Okay thanks! Will I be able to find where that is in the manual for the car?

 

the best source for detailed wiring diagrams is the specific electrical "green book" for your year/model. these show where all the grounds are.

on a 940, the main grounds are near the lower door hinge on each side (most stuff is grounded on the right side, cruise control, speedometer and ABS is grounded on the left), and the two main grounds on the engine are on the fuel injection rail, one is used for signal, and the other for power stuff. there are other grounds scattered around, like the main battery ground cable, the alternator-to-engine ground cable, the fuel pump grounds back in the trunk area, and so forth.

 

pierce is right on the Green book thing. I can't help much. I've worked with 200s and 700s but never done anything on a 900. If you don't have a green book for the car, you might ask around and see if someone around here knows more.

 

Thank you!