Odd misfire on a B20f

[doingitsideways]

Hi all,

My Celebration's started to run a little rough and has developed a misfire.

It's a little random in that is seems to come and go as it pleases.

Sometimes when idling it'll seem to go down to 3 cylinders for a bit, then pick itself back up.

Other times it'll manifest itself as a major misfire at part throttle, when either cruising of gently accellerating/decellerating.

There seems to be a slight cough when coming back on to the throttle after changing gear, but not all the time.

Doesn't seem to happen on hard accelleration.

Seems to get a lot worse when reversing for some reason, causing it to actually cut out a couple of times.


I've had a fiddle under the bonnet while it's running rough, all HT leads etc are secure, but if I move the wiring to the injectors it seems to get better, and then worse when I put it back.

This is making me think that there may be some sort of break in the wiring, but do they break down like that??

I suppose it's possible, the car's coming up to 150k and there's a lot of heat around there!

Any ideas anyone?

Cheers,

Steve

[jamesy12345]

Some good stuff here Steve although not for 400s

http://www.volvoclub.org.uk/faq/EngineF ... _Diagnosis

Looking on the net the idea for testing injector wiring seems to be that 12 volts is always supplied to the injector (when key is first turned/cranking/engine running), and the injection pulses are controlled by the ECU allowing a path to earth.

So maybe an idea to confirm what you are thinking is to use a multimeter to check for 12v at each connector while wiggling the wires?

Sorry if teaching you to suck eggs here

[doingitsideways]

Good thinking there James

Trouble with me is I automatically presume it's going to expire in a ball of flames, even with the simplest of faults!

Although, we are talking about 480s here, so anything's possible!!

Steve

[glasgowjim]

have answered on VOC forum

[doingitsideways]

Indeed you have Jim, but I'm curious about my rear mount now...

Do you suggest it purely because it's likely to be goosed due to age?

Steve

[glasgowjim]

No but it went on Skippy at one time and the engine shifted which didnt do the connections to the engine block a lot of good.

[jamesy12345]

eh how did we get to rear mounts....I better read VOC and be educated

edit: Jim, I guess you are thinking the engine block twisting/moving too far would stretch the wires, if the rear mount had some play in it?

[glasgowjim]

The rear mount snapped as they do from time to time and the vibration damper was goosed which caused the engine to gradually shift backwards at the drivers side by about 5 cm !

was not a good day when I noticed it

Surprisingly nothing was damaged

But it is always good to check these things . The defective wire could not be seen / noticed until the sensor plug was taken off and the wires waggled !

[doingitsideways]

Ah, ok then.

Thanks for the heads up!

Steve

[jamesy12345]

Thanks Jim. On my auto it's hard to tell the condition of the mounts and I was wondering about them - on manual cars excessive movement of the gearstick sometimes can be an indicator. I'll have to train the bairn up and ask him to look under the bonnet (from the side, at a safe distance!!) while I pull forwards a little...."stand there and tell me if the engine moves"

Let us know the verdict Steve when you get it

[Captain Slow]

...."stand there and tell me if the engine moves"

.....at the same speed as the car

[jamesy12345]

...."stand there and tell me if the engine moves"

.....at the same speed as the car

lol exactly my problem never work with women or kids