Hi all.

Failed IVA yesterday on emmissions and a few other easily fixable things.

I changed the plugs and i sounded like a different engine, much smoother, revs better, and needed the fuel setting up in megasquirt again (cylinders 1 and 4 weren't firing properly before changing the plugs).

After having it ticking over for a while and getting the map set up. The missfire has gradually started coming back at idle. If i rev the engine a bit, then let it idle, it's ok for a moment, then goes back to a slight missfire, causing the AFR to stutter as unburnt fuel goes into the exhaust.

Any ideas what could be causing this? I've already changed the coil pack, plugs and leads a while back, and another new set of plugs today.

Cheers for any tips.

Also, the compression tester ive got doesn't seem to fit into the zetec head, there doesn't seem to be enough threads on it.

Dave

[Edited on 11/6/11 by David_17]

just guessing but the condition that changed sounds like the engine reached normal operating temp?

does the mixture need to be leaned off to compensate?

Thanks for the reply.

I've tried all different mixtures, and pretty sure it's not that. I'll upload a vid, to show what's happening later tonight.

ok, perhaps an air leak around the intake manifold.

Here's a video of what's happening... http://www.youtube.com/watch?v=e3RvI76YlDE

I'm no expert, but as it happens, the revs seem to drop slightly - indicating unburnt fuel, not air?

maybe new coil and leads, or borrow a known working set?


A strobe on each ignition lead in turn might show up which cylinder is causing the problems.


Matt

Hi.

It's already had a new coil and leads, and i tried swapping an older coil i had spare yesterday, and still the same. Also did a compression test yesterday and all seemed ok. 160 on every cylinder.

Any tips on finding an inlet leak?

Are your plugs too cold a rating and therefore fouling up at idle?

How can i check that?

They're just standard ones for a zetec.

if changing the plugs cures it for a while it has got to be over fuelling. get ti down to a rr it will be cheaper than having to pay the full iva retest fee.