Misfire

[Guest]

My 1988 car has developed an annoying intermittent misfire. I have checked the standard things like plugs, leads, rotor arm, engine earth, fuel mixture etc. etc but still the problem persists.

If the car is used every day it runs perfectly, however if I leave it standing for a few weeks, and then use it, 5 times out of 10 it will misfire - particularly under load. The engine has always started first time and there are no signs of any problems when it is revved if stationary.

What really confuses me, is that if I turn the engine off when the car is missing, leave it for 10 minutes, and then restart it, the problem complete disappears. The car will then perform perfectly, even if left overnight. The whole cycle repeats itself however if left for a long period of time.

Please help !!!!

 

[Guest]

Scott,

Out of interest how have checked the mixture? With a colourtune? Unfortunately I can' t help with your problem. The only thing I can suggest checking is for dry joints on the DME relay, but only because others have had problem with this, in my case the car cut out when this happened not misfired. I have also heard that air leaks can cause poor running, but not really like those you describe.

Hopefully someone else will pitch up with something more useful to say on the matter.

regards

 

[Guest]

I had the mixture checked by a local garage who have an analyser.

Thanks,

Scott

 

[ClubSport 911]

Horrible Horrible Horrible....intermittent misfires are the worst of all. In 90%+ cases, they are electrical.

Replace plugs - just looking @ them doesn' t do the trick

Run the car @ night in the dark (sounds wierd) but then you can see if plug leads / distributor cap etc is breaking down. (look for blue arcs.)

Remove every connection you can see - spray WD40 - re-fit.

Replace (it;s cheap) rotor arm - Eurocarparts.co.uk

To be sure, replace distributor cap

Remove connections from DME - spray WD - re-fit

Don' t worry too much. The simple fact that it' s intermittent, means that the car CAN work fine, but something simple is preventing it from doing so.

I remember this kind of problem on my Cortina MkII...spent ages to find it was a 43p condensor....

All the best

STEVE