Bad Misfire

[WonkyGibbon]

Hello All,

Limped to work in the S today. I appreciate it can be practically anything but anyway - here are the facts :
- I use the car practically every day (but didn't yesterday)and she's usually very reliable.
- She was running very nicely the day before
- Unusually she was parked with her nose facing the road rather than the wall - which may have exposed the engine to more rain.
- Today, I couldn't get the revs above 2.5K even in neutral. Mostly it sounded strangled - but there were moments when there was a definate misfire going on. A very spluttery, lurchey mare of a journey

Any thoughts ?

Thanks in advance,

WG

[KentishS2]

Had exactly the same on motorway a few weeks back.

I put my foot on the loud pedal and it misfired as the revs increased.

It wouldn't do it around town ....just in the outside lane of the motorway!

I fitted a new TP on mine just after that and haven't had the problem again. Not sure if that was the cause though...

[WonkyGibbon]

KentishS2 said:

Had exactly the same on motorway a few weeks back. I put my foot on the loud pedal and it misfired as the revs increased. It wouldn't do it around town ....just in the outside lane of the motorway! I fitted a new TP on mine just after that and haven't had the problem again. Not sure if that was the cause though...

Mmm - that is quite odd. The TP was replaced two or three months ago, but the symptoms I'm getting are much more severe than what you describe - as though water has got into something it really shouldn't have ! Or air, or fuel or the spark or something, is getting restricted . It was a job getting her up to 30mph - I can't imagine what it would have been like on a motorway ...

[Podie]

Water by the distributor...?

[WonkyGibbon]

Podie said:

Water by the distributor...?

Could be - is that a known or common problem with S's kept outside ? Presumably I'd just need to take the cap off and have a peer inside to see if there was much moisture ?

[mowog]

I would start by checking all the HT related areas (coil, plugs, leads etc.) first.

I spent ages chasing a bad misfire under load last year only to find the main distributor was failing. This could only be established by getting an ignition trace/scope.

You could try unplugging the TP to see if that makes a difference.

plenty of info in the archives on TP and misfire issues.

Good luck!
Darren

[S3_Steve]

Had the same problem. One day she'd run fine, next day wouldn't rev, spluttering etc. then run as normal for a few miles. It was the coil breaking down, replaced, new leads etc.

[bridgdav]

Can be a common problem...

If the car is left nose down and it rains, the water runs straight onto the cap and leads...

If its left outside, localised silicone spray or dampstart would help keep the water out.

[Podie]

bridgdav said:

Can be a common problem... If the car is left nose down and it rains, the water runs straight onto the cap and leads... If its left outside, localised silicone spray or dampstart would help keep the water out.

Had the issue once... now have a small piece of rubber to stop water draining down by the distributor...

[WonkyGibbon]

Podie said:

bridgdav said: Can be a common problem... If the car is left nose down and it rains, the water runs straight onto the cap and leads... If its left outside, localised silicone spray or dampstart would help keep the water out. Had the issue once... now have a small piece of rubber to stop water draining down by the distributor...

Thanks guys (all round) - I'm going to hope that it isn't the coil / leads, on the grounds that it's not consistent (wasn't doing this tuesday).

Having just looked under the bonnet - bdy hell ! The distributor is basically a water catching dish for any run off from the windscreen - which nutter designed / positioned that !?! It's a bird bath !

Podie - your solution sounds spot on. Are there any issues I should be aware of when selecting a material for doing this - does this area get at all hot ?

Many thanks all,

WG

[M@H]

WonkyGibbon said:

Podie - your solution sounds spot on. Are there any issues I should be aware of when selecting a material for doing this - does this area get at all hot ?

it doesn't get that hot... I'd probably go with a bit of tyre inner tube, or some pond liner.

Cheers
Matt

[WonkyGibbon]

mowog said:

I would start by checking all the HT related areas (coil, plugs, leads etc.) first. I spent ages chasing a bad misfire under load last year only to find the main distributor was failing. This could only be established by getting an ignition trace/scope. You could try unplugging the TP to see if that makes a difference. plenty of info in the archives on TP and misfire issues. Good luck! Darren

Hmmm - well - took her out at lunch time, and she worked okay for about 100 yards and then started doing the same thing all over again all the way to my destination. Awful. Disconnected the TP on the way back and she drove perfectly.

I can't believe the TP has died in less than 3 months (and not that many miles either) particularly as it was perfectly alright two days ago. Am going to reconnect it before the journey home to see if it's still knackered. If it's not - could be moisture in the connector - if it is - could be dirt or some other contaminant (perhaps carbon deposits on the contacts like you get on a bad earth - which gets worse as it heats up - yes, that could be it - fits the symptoms) will test tonight and post if there's any success.

Cheers,

WG

[shnozz]

you would be surprised. leebee went through 3 TPs in 3 months. They are renowned for being generally crap and IIRC he fitted a cerbera TP in place of the ford item to solve the problem

[Podie]

WonkyGibbon said:

Podie said: bridgdav said: Can be a common problem... If the car is left nose down and it rains, the water runs straight onto the cap and leads... If its left outside, localised silicone spray or dampstart would help keep the water out. Had the issue once... now have a small piece of rubber to stop water draining down by the distributor... Thanks guys (all round) - I'm going to hope that it isn't the coil / leads, on the grounds that it's not consistent (wasn't doing this tuesday). Having just looked under the bonnet - bdy hell ! The distributor is basically a water catching dish for any run off from the windscreen - which nutter designed / positioned that !?! It's a bird bath ! Podie - your solution sounds spot on. Are there any issues I should be aware of when selecting a material for doing this - does this area get at all hot ? Many thanks all, WG

On some S's there is a small piece of rubber by the front wing to stop water... I just looked at Woolies trim and ended up getting some stuff from a local motor factors. No problems in the last 12 months, since I fitted it...!

[WonkyGibbon]

Oddly - I reconnected the Throttle Pot and it all started working exactly as it should. This would lead to the conclusion that the problem was to do with the connector - a poor contact being made due to the vibration - the resistance rising as the joint heats up. But this is all speculation.

But one lesson would be - clean up the connector just in case before lashing out another £50 on a TP.

WG