Misfire at idle. What would be the cause?

[Tom86]

I've notice this ever since I got the engine installed (Map 4agze). The engine would make a random popping sound from the exhaust at idle every now an then. It goes away when you driving ie would rev smoothly, but whenever I stop at the traffic light you can distictively hear the poping noise from the exhaust.

The spark plugs seem to be ok ie clean, but I've replace them anyway doesn't seem to make much different. Any ideas as to why this would happen?

Thanks

[lojik]

Are you getting a good spark? Is the coil doing its job properly?

Could be running rich at idle, and igniting unburnt fuel in the exhaust somewhere?

[Shifty]

It could be lots of things.

On one hand, a miss at idle was one of the first symptoms I noticed of the blown head gasket on my 22R... but on the other hand many cars with aftermarket exhausts simply have the odd pop, burble, etc and it could be nothing at all.

[merc-blue]

hard to start? = the coil

sooty exaust? = richness
then there is a mass of other possibilities

[Tom86]

hard to start? = the coil

sooty exaust? = richness
then there is a mass of other possibilities

Always start first turn of key, but the exhaust tip is rather black but it doesn't blow smoke or anything. The car is running standard computer, what would be the reason for it to run rich?

Also should I waste some money buying a need spark plug wires?

[toddw]

I would start with the basics - and my first place to look would be that of a vacuum leak. Manifold bolts are tight? Look for any vacuum hoses that have broken or fallen off. Just a thought.

Cheers

[Rallystanza]

As above, Have been told by a tuner that that a cacuum leak will cause a slight miss/pop at idle.

[sideshow]

what is the engine in
i know when u fit a gze into a sprinter the vac lines are a apin to do and also the intaske has to be spun roun d

this can cuase vac lines and ports to be wrong

[Ta2274Celica]

I have noticed the same thing with my Ta22... I replaced, leads, plugs, rotor, dizzy cap, points... so its either the gasket or the coil.... i will have to suss both of them out...

Peace.

[merc-blue]

Mate i would have done the coil first,
as visual inspection of dizzy cap, rotor and points can rule them out

[Ta2274Celica]

Mate i would have done the coil first,
as visual inspection of dizzy cap, rotor and points can rule them out

They were all pretty much dead... The metal piece on the end of the rotor had half broken off.. Haha, i couldnt stop laughing when i saw it the other day.