Strange issue, 98 v70 base

Solidar · Post by **Solidar** » 24 Apr 2017, 16:51

So i've been having this issue for a while. My CEL has been on for a while, its codes po300, 301, 302, 303, 304, 305, It's all misfire codes. So the issue being, the engine purrs, runs and idles smoothly with no fluctuating RPM whatsoever, what's even weirder is my CEL will randomly blink. Sitting in traffic, on the highway, at a stoplight, doesnt matter. But when the CEL blinks there is no impacted performance or misfire or anything, engine continues to idle smoothly with no fluctuation in RPM.

Things I've done:
-plugs
-wires
-cap
-rotor
-MAF sensor
-tested injectors
-cleaned injectors
-cleaned throttle body
-seafoam
-reset codes many many times

I'm really at a loss here, I'm going to try a fuel filter and another set of plugs but i've already tried about four sets of plugs already. I'm pulling my hair out on this one.

Post by **scot850** » 24 Apr 2017, 18:55

Have you checked the ECU connections? My current V70 project was bought with a flashing trans arrow and ECU problems. When the dealer removed them the mechanic found there was contact corrosion on the 2 units to the connector. He carefully cleaned them with a Wurth contact cleaner and cotton buds, refitted and removed them a couple of times to make sure the contacts were cleaned. He then removed the codes and all was good. The trans was working fine, as was the engine. However my Dice system checker could not communicate with the TCU at all.

Neil.

Post by **kahl** » 24 Apr 2017, 19:07

What brand plugs and plug wires did you use?

Solidar · Post by **Solidar** » 24 Apr 2017, 19:18

kahl wrote: ↑24 Apr 2017, 19:07 What brand plugs and plug wires did you use?

They were bosch branded wires I think, or at least OE equivalent, and i've tried 4 different sets of plugs with the same results.

Post by **kahl** » 24 Apr 2017, 19:53

These cars really like the Bougicord plug wires and the Volvo plugs. Over the years there have been numerous postings of our car's quirks regarding plugs and wires. On a 94 850 N/A I had similar issues until I changed to Volvo plugs and the Bougicord wires.

Post by **sleddriver** » 25 Apr 2017, 11:21

Solidar wrote: ↑24 Apr 2017, 16:51My CEL has been on for a while, its codes po300, 301, 302, 303, 304, 305, It's all misfire codes.

How's the wiring harness insulation for both the crank & camshaft position sensors? Be sure the coil wire is routed well away from this area as well.

Post by **850 LPT** » 26 Apr 2017, 07:40

This could be caused by a vacuum leak in the intake area. There are rubber hoses/ elbows that hook up to the intake and they can crack.

Another thing to check is injector seals. If they are old and briddle, they can leak and cause misfires.

Finally, and this is probably very unlikely, the intake gasket could fail and leak, which would cause your symtoms.

Good luck,

Dirk