engine missfires

hello i have a 94 spi cooper at say 30./40 mph she will missfire if then i give her plenty of acceleration this clears and say at 60mph she runs fine i have changed ,plus/leads/ dizzy cap/s
rotor/ coil. it also surges on tickover any ideas please thankyou..tonymap

Alright Tony, If you haven't already check for air leaks spi's seem to be prone to it, vacuum pipes at the bulkhead can come off or split and just check the manifold nuts are tight as they can work loose.

Matt wrote:Alright Tony, If you haven't already check for air leaks spi's seem to be prone to it, vacuum pipes at the bulkhead can come off or split and just check the manifold nuts are tight as they can work loose.

hello thankyou will check round in the morning thankyou..tony

hello having looked as best i can i cant see any problems with pipes all seems in order i did notice that the lambah sencor isnt much fun to get at ..iv had the cat put back on not sure if it will make any difference..thankyou..tony

Ive got diagnostics kit for spi's, I can check for faults and run actuation tests, see if anything shows up. Im out near Eardisley if you fancy bringing her out.

Sidney wrote:Ive got diagnostics kit for spi's, I can check for faults and run actuation tests, see if anything shows up. Im out near Eardisley if you fancy bringing her out.

HELLO thankyou for your kind offer i dont know where eardsley is..tony

Out towards Kington, where are you? Cant promise to get to the bottom of it, but will have a good go.

Sidney wrote:Out towards Kington, where are you? Cant promise to get to the bottom of it, but will have a good go.

HELLO SORRY I STILL NOT SURE WHERE YOU ARE IM NEAR LINCOLN THANKYOU..TONY

Ah I see, sorry thought you were local to me! I wont be a lot of use to you! But I have a few things you may wish to try:

firstly very simple, the main plug going into the ecu doesnt always locate properly if it has been disconected at some point, and can cause the symtoms you mention, just whip the plug out check the metal connectors arnt excessively dirty and corroded (unlikely) and refit fit firmly wiggling it all the way in until you feel a faint click.

As said before check vacuum pipes, especialy the long pipe with a fuel trap that comes back to the ecu.may want removing and blowing through to check its not clogged.

Another known problem is failure of the fuel trap on this pipe letting small amounts of fuel back along the pipe into ecu... easy fix... remove the whole ecu box and place on a warm radiaor overnight then refit. Also fit a new fuel trap just to be sure.

If no joy then find someone with mems diagnostics... probably a sensor.

hope this helps, Sid

Sidney wrote:Ah I see, sorry thought you were local to me! I wont be a lot of use to you! But I have a few things you may wish to try:

firstly very simple, the main plug going into the ecu doesnt always locate properly if it has been disconected at some point, and can cause the symtoms you mention, just whip the plug out check the metal connectors arnt excessively dirty and corroded (unlikely) and refit fit firmly wiggling it all the way in until you feel a faint click.

As said before check vacuum pipes, especialy the long pipe with a fuel trap that comes back to the ecu.may want removing and blowing through to check its not clogged.

Another known problem is failure of the fuel trap on this pipe letting small amounts of fuel back along the pipe into ecu... easy fix... remove the whole ecu box and place on a warm radiaor overnight then refit. Also fit a new fuel trap just to be sure.

If no joy then find someone with mems diagnostics... probably a sensor.

hope this helps, Sid

HELLO i took her out the other day she ran very bad so came back i did actualy blow through said pipe whent out again she ran very well no probs next time out ran well but had her ticking over for a bout 15 mins waiting in the cold for some one she then run very badly again havent loked at her again yet but seems from what you say ..fuel trap needed.thankyou..tony

no worries, hope you get it sorted, if you do replace trap it is worth doing the radiator thing overnight too.