Had a '95 850 non-turbo for a couple months now. Have replaced plugs, wires, MAF, rotor arm, distributor cap, timing belt, serpentine belt and cleaned the idle air control valve, EGR valve and throttle body. It starts a little rough, runs fine at idle and starts missing (hesitating, stumbling) when i try to go forward. More so if I'm heavy on the throttle. It threw a P0300 (multiple cylinder misfire) while I was on the highway but I cleared it and it hasnt come back. I cant find any vacuum leaks, ive verified the firing order, gave it a seafoam treatment (gas tank and vacuum in), checked all the plug gaps and wire connections. Im stumped. please help.

 

Hi Jordan, welcome to the forum.

First off, you should know that these white block Volvo's (I5 & I6 found in the 850's and 960's) are picking about ignition parts. So, I only use Volvo plugs. Many have had success with standard copper tip Bosch and Champions. Then you have wires, use Volvo or Bougicord. Cap and rotor should only be Bosch. So, if you have done anything other than that, you may want to redo.

If that doesn't do it, try doing a compression test. These cars are known for having burnt valves.

 

I just ordered oem plugs, ill try that and let you know. Thank you for your help. Almost all of the work I have done on this car have been from your videos.

 

Once you have the plugs replaced I'd do a compression test to make sure you have all five at the same level.

I know you put seafoam in the tank and it's a nice product but you might want to go back and drop in a dedicated fuel injector cleaner like Lucas or Chevron. They just do a better job of cleaning up a problem if you have a gummed up injector that's leaking or spraying poorly.
I like the Lucas and it's fairly cheap if you get it by the quart compared to the "single serving" size.

If you're still having an intermittent misfire and it starts a little rough for all the work and parts you have in there I'd check the coolant temperature sensor to see if maybe it's off. It might not be bad enough to set a code but might still be bad enough to lean or richen up the mixture to give you some trouble at start up and maybe under load.

 

Got the new plugs in, and it works great. Thank you for your help!

 

What brand spark plugs were you using ??

 

I think he got the OEM Volvo plugs.

 

What brand spark plugs were you using ??

I'm curious what was only a couple months old and didn't work.

 

another question is what was the gap on the plugs that didnt work.

 

I was using Autolite coppers, and the gap on all of them was between .74 and .76mm. based on the Haynes Manual spec on .7-.8mm. They stopped working after less than 50 miles. Not saying anything against autolite though, ive had the same plugs in my tacoma for years. Its just one of those volvo quirks.

 

I'm running AC Delco Platinum with no problems. Just curious what doesn't work for some people.

 

The owners manual says the gap for the 850's is 0.7mm so that was right on.

 

I put in Bosch Superplus that came with a .9 gap. Runs great.

 

0.76 mm is about 0.030" and as I remember the gap on these cars shall be 0.028"; not 0.029", not 0.030", etc.

 

^^^ one of my favorites!


.028 is where they should be for stock.

Over the years and messing with multiple ranges of gaps I am running copper plugs gapped at .023