2000 Volvos S80 misfire

jaru · Post by **jaru** » 07 Apr 2015, 17:40

Hello, I'm new here and hope someone is able to help me figure out what the problem might be.
The problem started out like this: First the ABS fault indicator came on, but car was still drivable.
Then the car was restricted to 1500-2000 rpm and the transmission would not shift.
All the spark plugs and some ignition coils were replaced and the the car wouldn't start anymore.
This is the story my step son told me who was the owner before he gave it to me.
When I started working on it I tried to read out any error codes with the OBD II scanner, but it showed on codes. The motor cranks over, the fuel pressure is 50 psi, I have spark on all 6 cylinders and the injection valves work.
Now here is the strange thing. While testing all the spark plugs I removed one spark plug at the time and to my suprise I was able to start the engine every time. I doesn't matter what plug I remove as long as I remove at least one. It will even start with only 4 spark plugs, but will not start with all 6 plugs being installed. For a long time I was not able to give it gas or it would die and I still didn't get any trouble codes. Recently something has changed. I still have to remove at least one plug to start it, but now I can run it up to 1500 - 2000 rpm and I'm getting P0304 P0303 and sometimes I can get it started with all 6 spark plugs installed, but then I will get code P0300.
Thanks for any help!

draser · Post by **draser** » 09 Apr 2015, 07:13

Can you read freeze frames, that get saved in ecu when there's a code, with that scanner? That'll show more info of what's going on with engine. Did you check for air leaks - all vac lines in, tight clamps, etc.?

jaru · Post by **jaru** » 09 Apr 2015, 10:32

No I'm unable to read freeze frames. I checked for air leaks and didn't find any. Thanks for the help!

draser · Post by **draser** » 09 Apr 2015, 11:53

Based on vintage there are some miles on the engine, so I'd do a compression test to assess condition, you could borrow a gage from AZ or the like. Turbo or N/A? I'd check timing marks as well.

jaru · Post by **jaru** » 09 Apr 2015, 18:30

Thanks again, any idea why I"m always able to start the engine with at least 1 spark plug out, but usually not when 6 plugs are installed?

matt5112 · Post by **matt5112** » 09 Apr 2015, 20:02

Double check the connectors at cylinders 4 and 5. I believe those are the two that are easy to connect to the wrong spot.

draser · Post by **draser** » 10 Apr 2015, 05:25

It sounds like spark occurs on piston's way up and engine can't overcome due to low compression, so firing order like said, timing and low compression would play a role.

Post by **precopster** » 10 Apr 2015, 06:44

Has the ETM (electronic throttle) been verified as working correctly? Does it click on and shut back off after 10 secs with ignition on and engine off. Does throttle flap move when accelerator pedal is depressed (you only have 10secs to test this with engine off)

Remove MAF connector and see if engine starts and runs better. ETM can cause misfires however given the strange behaviour I would get a compression test also.

jaru · Post by **jaru** » 11 Apr 2015, 20:53

Thanks everyone, ETM works fine. Will get an OBDII reader with freeze frame capablities. I will
troubleshoot coming week and post again.

draser · Post by **draser** » 12 Apr 2015, 14:08

Can you verify your firing order, or coils not switched between adjacent cyls? You need a running engine to use scanner.