hi all,

 

ive got this slight miss fire on my 1990 uk tt auto, i think ive narrowed it down to the LHS bank of cylinders ( drivers side ), the way i did this was to slightly rev the the RHS bank, i think this lets the air in to the plennum feedding the opposite side, i hope im right !!! :nelson:

 

right then doing this i get the miss fire, so i disconnected the coil packs one by one and the revs dropped on all six cyllinders, next i disconnected the injectors and cleaned the terminals and tried again but to no avail. :cry:

 

i also put a long screwdriver against the injectors and put the other end against my ear and could listen to the injectors clicking away!!

 

well im doing my nut trying to find this missfire so any help would be much appreceated :hyper:

try changing the plugs - thats what cured mine.

Sounds daft, maybe I read it wrong, but if the revs dropped on all six cylinders when you disconnected the coil packs, then you don't have a miss-fire :confused:

Have you tried disconnecting, cleaning the connector, and then reconnecting the PTU?

 

Worth a go!

andyduff, yeah i know it sounds wierd thats why i cant trace the damn fault, my next step will be to swap all the plugs round and to clean the connections on the ptu, thanks guys i'll let you know how i get on. :hyper:

Hi mate, i hope it's not the case but i've had this fault more than once on renault engines at work, you can hear a mis-fire through the exhaust but removing each lead gives a change in engine tone/rpm, the fault in their case is a burnt/cracked valve. :cry: .. A compression test will be the easiest way to find it if it is.

 

Baz

Thats what I was starting to think Baz :(

ok story so far, have removed ptu & cleaned all connections, i dont get the missfire when i first start up the engine only when it has warmed up !!!,

i also swapped all the plugs and coil packs from left to right side and the problem is still there when i rev the passenger side throttle body, so its not the plugs or coil packs, could it be the ptu, or an injector??

 

i can try a commpression check but it seems to be ok when its cold!!! :cry: :cry:

The crack is usualy in the exhaust valve and will be expanding as the engine warms up, the compression test would have to be done when the engine is hot and showing the fault.

 

Baz

Hmmmm check the injector resistances at the ecu loom when the engine has warmed up....