Pesky misfire

[MarkyB]

After several goes I got this sorted.
As it seemed to have appeared after changing to an electronic distributor so I had been looking in the wrong place, the ignition side.

It manifested as a misfire that felt like all 4 cylinders didn't fire for one or two revs or just rough running when giving it some stick in 3rd, somewhat temperature related too.

Turned out to be this;[frame][/frame]

It's the wire to the petrol pump and had been working for many years although that plastic sleeve was mostly insulating the flat faces.
I guess spark erosion did for what ever bit had been connecting which luckily caused the car to poop out completely, that's what put me on the right track.

[Chipper]

Ah, that'll be the patented SU fuel-saving measure.

[millerman]

MarkyB, you are now sorted for Brittany

[MarkyB]

Exactly Millerman, it's a relief to have it sorted in time .

[surfergirl]

I had a similar problem with a pump on a saloon years ago, which misfired and would conk out every now and then. Turned out to be sticking points in the pump, used to get home sometimes by the passenger hitting the bulkhead everytime we needed fuel to pump, resulted in a sore hand!

Whats the heat wrap on the exhaust in the photo?
Cheers.

[MarkyB]

The pump itself is pretty new so I wouldn't expect issues with it.
It's exhaust wrap I bought on ebay, this car really doesn't like hot days in traffic and it helped a bit to keep engine bay temperatures down.

[MarkyB]

Well that fixed the mis-fire and poop out scenario at least.
What has remained is another one which although mostly alleviated still rears its ugly head some times.
It got progressively worse going through France until I spotted a burn mark on the corner of the rotor arm and deduced that the spark was having to jump some distance and not always making it.
This was verified by cleaning the mark off with a nail file, this made it much worse!
At the moment I've run the knurled nut all the way to A and the mis-fire is all but gone.
It now only happens at very random times if at all, yesterday it didn't miss a beat, today it's missed two or 3 times mostly in 3rd gear accelerating.

I expect the answer is going to be take the distributor drive gear out and move it around one tooth to bring things into better alignment.
Not really keen to mess with it this far from home

[bmcecosse]

Moving the drive gear round won't make a blind bit of difference! Fit a new rotor arm and check the mechanical and vacuum advance systems are working....

[MarkyB]

The whole distributor is brand new, red rotor arm.
I have the old rotor arm so could try that.

At the moment it just misses a beat very randomly.
Plugs and leads have been on there a while but all look fine.

[chesney]

I was once dogged by a missfire that left me stranded in a car park, lack of torches and bad weather made me walk a mile home and recommence the next morning. Having changed every ignition component and still not getting a spark, I worked out that 2 of the gen Champion plugs I'd fitted had given up - a week after fitted them! A set of old Autolite AL5's from the toolbox got me home.
Anyway, my point is that it can be the least likely things to go, so look out for them!
I got so desperate I nearly contemplated changing the coil!

[Chipper]

S*d walking home a mile in the rain because of a misfire. I would have driven it on the 2 cylinders.

[chesney]

We have hills in Yorkshire though ;)

[Chipper]

I once drove my long-suffering Traveller all the way down the A13 in Essex in the dark after the cylinder head gasket went between the middle two cylinders. It got me home to Westcliff-on-Sea, and the next day I drove it 4 miles to work in Hadleigh and dropped it off at the garage there for a replacement.

They're pretty tough, A-series engines.

[bmcecosse]

That's really not wise - the head and block are very likely to be scoured by the hot gases - meaning a much more expensive repair will be required.

[chesney]

Indeed, as BMC states. I'd never think not worth the risk myself, certainly not worth ruining the block over a head gasket......

[bmcecosse]

To get back on track...Marky - try new leads and plugs..........

[MarkyB]

Further investigation and tinkering seems to have sorted it out.
The module in the distributor had been on the move and ended up touching the central spindle.
I moved it back into the proper position (and tightened the screw up properly) which advanced the timing a massive amount such that it would kick back against the starter motor.
Retarded the timing from kicking back, to spinning over at great speed but not catching, to running.
Looking at the timing marks it still seems to be very far advanced but starts and runs well (for and hour and a half drive anyway) without a single mis-fire.
The plan at the moment is to fill up with 95 RON rather than 98 to provoke some pinking and time it to get rid of that.

[bmcecosse]

Unless you have a highly modified engine - 95 petrol is the one to use -ALL the time! Well done sorting it all out - so far.......