1996 850 Base NA Severe Misfire after smooth running

zupta82 · Post by **zupta82** » 03 Mar 2019, 07:58

Also, I use 87 octane usually and sometimes 93. I changed the fuel filter several months ago . I was wondering could water build build up in the filter from poor quality gas in a matter of months??

Post by **erikv11** » 03 Mar 2019, 08:02

The water buildup seems unlikely to me but not sure.

A 96 850 should not have a fuel pressure dampener, just a Fuel Pressure Regulator (FPR). FPR should be either in the fuel rail, at the back of the subframe on the passenger side of the engine bay where the fuel lines come up from the tank, or back near the fuel filter. I'd check those places in that order. Don't get fooled by the rollover valve back there by the fuel filter, it isn't an FPR or a dampener.

zupta82 · Post by **zupta82** » 03 Mar 2019, 09:13

Can I check the regulator with the use of a vacuum pump

Post by **abscate** » 03 Mar 2019, 12:51

Bad gas is usually a bad diagnosis. Check the FPR by smelling it for liquid fuel inside, that's the failure mode

zupta82 · Post by **zupta82** » 03 Mar 2019, 14:50

I took it for a drive just to see if it would throw a code and had very little power the check engine light came on and I got misfire on cylinder 2. I took out the plug on cylinder 2 and it was slightly black . On a whim I replaced the injector with an old one I had laying around and it ran better. I hooked up a vacuum gauge and it was pulling in about in about 18 pounds and it was steady I shut it off for about an hour came back and started it back up and it did the same again

tardcart · Post by **tardcart** » 03 Mar 2019, 15:06

to check the regulator for leaky diaphragm just pull the regulator 5mm hose off the tree b¥ the throttle body and suck on it. if gas goes in your mouth or it doesn't hold a vacuum, it's bad. to check timing just take the 12mm bolt off front cover, turn wheel hard right and lift mud flap (one bolt) and use a socket to turn crank clockwise until the timing mark on the face of the pulley lines up with the forward timing belt. then see if the two cam gears are on the marks. You can peer in with a flash light to see the real timing marks on the gear to make sure the damper hasn't shifted. I dont think thats a problem with the 850s though.

zupta82 · Post by **zupta82** » 04 Mar 2019, 05:26

I checked the timing and the regulator and they seem fine. I took a second look in the distributor cap and found about a tablespoon of water in it this time. The cap is about 6 months old. From my research there seems to be a plastic dome shaped thing under the cap that acts as a shield/seal. I reused the old one, a new one was not included with cap. Also, it seems to be missing a large o-ring that goes on this plastic dome. I looked everywhere online and can’t seem to find a new one to buy

Post by **abscate** » 04 Mar 2019, 05:36

Get the parts explosion off the Volvo parts Lisle site to get Volvo part numbers

Post by **erikv11** » 04 Mar 2019, 07:02

erikv11 wrote: ↑24 Feb 2019, 22:16 Are you sure the cam seal is not blown out under the distributor cap, sending in moisture and oil?

The moisture is not likely coming from outside air, but from the engine combustion.

Take the dome to a machine shop and ask for an o-ring that fits. Or get another dome from a junker, these don't typically go bad.

zupta82 · Post by **zupta82** » 05 Mar 2019, 20:26

Update: I went to the junkyard and found when of them “saucer” like things for the distributor with a good o-ring. I buttoned everything up with the dried out distributor cap, thought I was out of the woods. The car started up fast and had tons of power after about 20-25 minute ride it started misfiring again.

1996 850 Base NA Severe Misfire after smooth running

Re: Severe Misfire