Firstly, I think this could be the correct forum to post this question, I've searched a bit but cant find anything. Moderators feel free to move the thread if needed.

Anyway EF 5 speed Wagon, seemingly at random it has a missfire usually when taking off or accelerating after a corner. It seems to get worse as it gets warmer although temperature doesnt really seem to be much of an issue. Sometimes it will allow full throttle runs without a problem while other times it misses and backfires.

I got the car with a blown engine just over a year ago, reco'd the injectors when it went in, sparkplugs etc. as usual, engine was fropm an auto but seemed to run fine for the first 10 months or so. I think the problem started when I had the dash out to repair the broken pedal box.

I have changed the TPS with a good one, replaced the fuel filter and tested fuel presure, and replaced the coil pack and HT leads (also rechecked the sparkplugs still look almost new), all made no noticeable difference.

Last week I fitted new battery terminals and upgraded the body earth from the battery, it seemed to make it a little better, but still not perfect. I also checked the charge rate and its a little low, around 13.8-14.0V, will the low charge voltage cause issues at all?? and where are my other earth points so I can clean them jup and make sure they are earthed correctly?? Also the odo backlights dim slightly when using the indicators.

Could be a Crook Coilpak start it up tonite in the dark and check for any little sparks across the leads and the coilpak.

Checked coilpacks for spark in the dark, both the old and the new have no signs of tracking or burning on them.

Dirty throttle body possibly.
Had this problem this week. The car when warm would surge and miss underload. And miss at idle and stall.
Put a can of direct throttle body cleaner through.
Idles perfectly. No missing. And the powers back.
I was suprised how much difference it made. And how much black smoke.

I'll gtry that tomorrow thanks, I didnt think it would be just a dirty throttle body as idle is about the only time its always good, but you never know.

Id be looking at the coil packs unless you have swapped them already.

I didn't think its be that either. But since I had new leads and plugs I had no idea what it could be.
Head mechanic at work diagnosed it as soon as I brought the car in.
But since you said it idles fine id be thinking ignition.
How old are you're leads and plugs?

Hi mate,

I've been having a very similar problem with my EF. Under load/heavy acceleration there's usually no problems, but when accelerating lightly it will sometimes misfire or hesitate.

Sometimes I can hear and feel a slight misfire at idle as well.

Seems to come and go. So far I've changed O2 sensor, plugs, leads, and fuel filter. It seems to be almost or completely gone since changing the fuel filter yesterday, but I'll let you know after a bit more testing. Strangely enough I only started noticing this problem a few days after I had extractors and exhaust fitted last weekend. Maybe the problem was always there and the exhaust just makes it more noticeable..

Anyway I'll let you know when I work out what's causing mine!

Cheers

inlet manifold gasket. will explain the way it clears up at WOT conditions

little red wagon,

Just letting you know I found what was causing my misfire problem, in case it helps you too, from my thread:

http://www.fordmods.com/ford-4l-and-6-cylinder-f1/ef-hesitating-misfiring-since-new-extractors-exhaust-fitted-t96783.html



Hope it helps.

Cheers.

Thanks Tragilgas, I will try some 98 next time we fill up.

Funny though, everything here runs on premium because we have non-sniffable Opal 91 octane which is good at killing fuel systems (I dont think its ethanol but sounds like it does the same sort of thing)

As for plugs etc. plugs were new a year ago and still look close to new, leads and coilpack wwere the first things I tried.

It did seem to get better when I put new battery terminals and new body earth, but still not perfect, I think I have some poor earths in the loom, I refitted all the earths I disconnected when I had the dash out, but I cant say the previous guy that had the dash out didnt miss any. (I know the history of the vehicle)