Misfiring 480

[doingitsideways]

Hi all,

My Celebration's started to run a little rough and has developed a misfire (2.0/B20f)

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

[dcw]

I've got an idea Steve, buy Morwenna!

All joking aside, it does sound a bit like you have some wiring deteriorating - all wiring can gradually break down with time and heat.

If that's the case it could be a pig to track down any particularly dodgy part, but if you can find a scrap yard case then any 400 series with that engine should have the same loom. Just need to be methodical then with replacing it.

I haven't bothered mentioning things like idle valve/throttle valve, since I assume you have checked they are clean and anyway you sound to have a specific symptom with the wiring...

David

[jeff t]

Put a spare dizzy cap on just to make sure no crack, had a problem quite like it and dizzy cap looked ok but changed it just to make sure and problem sorted.

[glasgowjim]

Sounds like a problem I had on daughters last 2ltr 480 . An intermittent fault hence the cars name skippy. Turned out to be very simple. The sensor connection next to cylinder number 1 (nearest the distributor cap) the wire had become brittle and snapped but it was making intermittent breaks in contact hence the misfire like the car was sneezing. It happened at all sorts of odd times with no pattern. Oh check your rear engine mount as well .

[doingitsideways]

Cheers for the replies,

Jim, sounds like sound advice, but how would the rear engine mount cause this?

Oh, don't suppose you've got the section of loom in you magical shed by any chance?!

Steve

[Clan]

Originally Posted by doingitsideways

Hi all,

My Celebration's started to run a little rough and has developed a misfire (2.0/B20f)

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

I changed quite a few of those injector looms when the 480 was current for that problem . The connector would move in and out when the engine moved and it eventualy wore away the pins in the plug . the distributor cap should be changed avery 2 years for reliability .

[skipy]

My turbo has a similar problem.
When at normal operating temperature at idle I can sometimes notice a missfire. The engine cannot stay in the same RPM. There's also the case that when i stop, the engine revs up and down a few times before idling. This hapens not very often however fuel comsumption is starting to get bad. I'm experiencing 22mpg (infocenter) although i mostly drive on the city and for short distances (4~6 miles) and driving in conservative manner.
I'm starting to believe that the problem is with the acceleration; at constant speed I can get regular values but when accelerating it seems that i'ts consuming more than ususal. As you may know the trip computer checks the instant fuel comsumption based on distance travled; i.e., every 30 meters (sorry not from UK) the instantaneous comsumption is checked. I get the maximum value the computer can show(25.5l/100 ~ 11mpg) in two or three refreshes (so between 60 and 90m) at normal operating temp. I know it's hard to tell, but aren't these excessive?
So the problem is mostly related with acceleration. constant speed seems to give the same mpg as i'm used to.
Everything spark related is less than a year hold except for the coil. Throtle body is reconditioned. ICV is OK. No vacuum leaks that I can find. Is there anything else I should be looking?
Thanks and cheers

[skipy]

Hi, things have gone much worse since my last post.
on sunday the car started stalling at idle when stuck on trafic. It stated by missing one stroke now and then but sonn enough it got even worse: the engine started to speedup in one second than the in the next second it returned to normal revs and then speed up again in the next second. And it kept in this loop for a minute or two but each time getting worse. after two mins I could see the turbo dial moving a little bit up and down. Once i got out of trafic and in the highway it still missfired a lot of times but not as bad as when in iddle.
As a test i pushed the pedal to full throttle progressivelly. what i could find was that the engine would cut-off/stall even worse at full throttle (not rev related I think).
When I got home, i tried cleaning the temp sensor terminals near spark plug #1 as I was under the impression that it only happened at normal operating temp which could indicate that the engine "thought" it was cold. After the engine cooled down, I took it for a test drive and It appeared to be ok. Tried to stay at idle some time and it seemed ok.
Today, I was stuck on traffic again and the engine started to get worse again and stalled. I went to work with the car jumping (and stalling when off throttle).
After cooling down I turned it on but no joy, the engine was still misfiring a lot and stalling. So I think It's not the sensor. However after 3 mins of driving it went back to close to normal.
I know I'm being tedious but can anyone confirm if I am correct in rulling out the temp sensor? Can it be something else?
Cheers

[doingitsideways]

Hmm...

Afraid I can't really help much.

But I'd check the wiring to the temp sensor, on my 460 Turbo it had broken where it enters the plug.

Apart from that, a sensor is reasonably cheap and easy to change, so I'd give it a go

Good luck!

Steve

[skipy]

Thanks for your reply.
This weekend i'll try to have a better look at the cables. I'm not sure how it connects to the ecu otherwise i would replace the sensor's wires completely.
While I'm at it, Do you think there's something else worth checking? I'm clueless.