1995 850 Random Stalling and No Start Condition

[blackmoor]

95 854 N/A 212,000 miles

While driving this car will sometimes lose power for just a second. Sometimes it will do that once or twice, and then run perfectly for the rest of the day. Sometimes it will do that once or twice, and then just completely die. After pulling over, it sometimes starts right back up, but usually it will not. After waiting for anywhere from 10 minutes to a half hour, it will start right back up like nothing was ever wrong. It seems to happen most frequently 20 minutes or so after starting and it has never stalled/no start after running okay for more than 30 minutes or so.

I've personally changed the fuel pump relay and the auctioneer said the wires, plugs, and fuel filter were new. They certainly appear to be new. The problem is that with the random nature of the problem, I have a hard time troubleshooting. I cannot reliably cause the stall or no start and it has never happened while it is just idling in my driveway, sometimes for a couple of hours.

I'm not a real good mechanic, and usually fix things through pure stubborn-headedness. Any advice on what I can do next would be greatly appreciated.

[Ozark Lee]

Is your Check Engine light on?

There are a number of things that could cause your problem but codes would really help. Since you have a '95 you have the code reader built into the car under the hood.

The DTC box is just behind the windshield wiper fluid filler top and it is marked A and B.

Put the flywire into port A-2 and see if you have any codes. Also try port A-6, it may or may not read anything but we need to know if that port is active to make sense of the other codes.

To read the codes press the button next to the letter A and then use a pen and paper to write down the flash sequence. There may be more than one code so write down all of the sequences. They are all three digit codes.

...Lee

[blackmoor]

I knew I forgot something. I had checked the codes and neglected to include them with my earlier post.

They were:
542 Misfire more than one cylinder
543 Misfire at least one cylinder
452 Misfire cylinder 2
453 Misfire cylinder 3
131 RPM sensor signal missing
214 RPM sensor signal sporadic

I cleared those codes and drove it again until it died on me. The only code returned then was 131.

[Ozark Lee]

The misfire codes are more of a symptom than a problem itself. The crankshaft position sensor though will cause the problems you describe.

Check the wiring from the RPM (Crankshaft Position) sensor first and pay attention to the routing of the wires. There was a TSB that called for using a Ty Wrap to keep the wires from both the camshaft and crankshaft position sensors away from the ignition wires. In their natural state they want to loop up next to the coil wire and the ignition pulses can cause interference to the sensor signal.

You pointed out ignition items that were changed prior to you buying the car. Do you know what brand the ignition wires are? Anything but Bougicord wires will cause grief and the cars are also incredibly picky about spark plugs and spark plug gap (0.028"). If something like Bosch +2 or +4 plugs got put in it will never run right since those are preset to a gap of about 0.045".

...Lee

[blackmoor]

I checked the wires from the crankshaft and camshaft sensors. They were not very close to the ignition wires. I measured around 300 ohms between the two leads on the crankshaft sensor. I probably should also have mentioned this earlier, but the tach doesn't register anything. Is there a procedure for troubleshooting the wiring from the sensor to wherever it goes, or is it just a matter of following it and testing continuity at plug ends?

Also, the plug wires are Autolite. I didn't check the plugs themselves but I'm assuming they're not going to be Volvo.

Thanks for all your help so far.

[E Showell]

These cars hate aftermarket plug wires. With them out for a set of Bougicords. I had a random dying issue on a '96 850 wagon that turned out to be a negative battery cable corroded completely through where it bolted to the front subframe as it headed to the starter. Can would periodically die in traffic when the wire vibrated away from a position where it was making contact. You might want to trace your negative battery cable both the ground on the frame by the battery and as it heads for the starter.

[Ozark Lee]

You really need an oscilloscope to check the camshaft and crankshaft sensor signals so that you can see the pulse, an ohmmeter doesn't tell the whole story. If it were me, with your symptoms, codes, and no tachometer, I would replace the crankshaft position sensor. That sensor is fairly pricey but if you have a Pick-N-Pull type lot locally it is an easy one to snag for a lot less money.

From there you need to pull the spark plugs and check the gap. Most people just pull spark plugs out of the box and screw them in and typically they come out of the box at 0.040 to 0.045 which is fine for a Chevy or a Ford but not a Volvo 850. Most of us don't run Autolite spark plugs but they should work OK if they are a single electrode and they are gapped properly. I run the really cheap Bosch copper cores in my N/A car and even one of the turbos.

...Lee