The engine has just been rebuilt and almost run-in and performs perfectly whilst on the move. The following problem has occurred twice when I'm in stuck in a traffic jam with stop/start movement and longish periods on tick-over. The car starts to develop a misfire and when revved in an attempt to clear it, it struggles to increase the revs and backfires through the exhaust very loudly and repeatedly. Eventually, the engines reduces to what sounds like 1 cylinder and dies. If then left for some 15 mins, it fires up normally and drives fine provided that a clear road is found. It sounds fuel related to me as the exhaust tailpipe tends to be overly black but I'm not sure where to check for a fault(s). It may of course be some electrical/sensor problem which only manifests itself when under-bonnet temperatures rise above those whilst on the move. I should add that the temp gauge does not display any over-heating, there is no discharge of the cooling system and the thermostatic fans switch on and off as normal.

My engine runs 803 injectors and a Bayjoo chip and prior to dismantling and re-assembly, never suffered from this fault. Obviously the extensive disturbance/disconnection of the various loom components may have caused some problem but I feel that this is an overfuelling fault causing the plugs to foul and once left to cool/dry, they return to normal. However, would this result in severe backfiring?

I should add that I changed the plugs after the first occasion to no avail.

Any suggestions/guidance would be greatly appreciated.

 

What plus are you using, what gap, it does sound as though it is VERY rich, not unusual with a lot of chips done as a protection thing, but shouldn't be to this extent.
I would check the CTS connector, and the map, tps as well, see if any have broken wires.
I would also unless new replace the CTS sensor, only around £10 from matt lewis 01922 692424, as these usually go tits up and mega rich.
Then get you co checked, and set around 2.5% co.
tabetha

 

Thanks for that and I've ordered a CTS accordingly. In relation to plug type, I've tried NGK -9, Champion 57 and Ford 0071, all new and gapped at 40 thou.
Fingers crossed that the CTS does the business.

 

hi there i just came across a problem you posted in 2008 i have exact same problem with my cosworth it drives perfect until you get held in traffic or leave to tick over for a while.it then runs terrible and misfires .if you leave to ciil for 15 mins its grand again .what did you find was causing this problem .any help would be appreciated.

 

I had same problem on my 3 door a couple of years ago, eventually it gave up all together, took a long time to solve it but mine ended up being a fault in the phase sensor that was breaking down when it got hot, I fitted a new one gapped and timed correctly and it fired up, no issues since but could be any sensor causing problems, or even the loom or connections, just try cleaning and checking gaps on crank and phase sensor then check all plugs and loom connections.