Civic EG

So i did the FIAV delete / bypass recently, and did a full rebuild on the top end. On cold start the car runs like a champ, but as soon as it gets to operating temp it starts to misfire. I have checked the plugs which are brandnew, and all look fine, checked resistant on the coil wires and they are in spec. New cap n rotor, did a compression test and the numbers are ok.

So what else could it be?

I was thinking maybe a clogged injectors, bad fuel filter, or fuel pump screen clogged. It seems to idle perfectly with a slight drop of rpm… Not psychically noticeable on the tac, but you can hear the blip in rpm drop. Then when giving it gas it hesitates, by having that sluggish misfire feeling… like the spark, no spark, and then once I hit a certain rpm range it goes away.

what all did you do in the full rebuild of the top end?

did you set the timing correctly?

the head was hot tanked, bead blasted, all the exhaust guides swapped out, 3 angle valve job, and resurfaced. Stock valves were cleaned up. Then pressure tested.

timing is spot on. timing marks match up. the only thing else is maybe something bad with the fuel system. the car has 265k on it. so i am not sure about it's past and who took care of what.

i will check valve lash later this week when i get a chance. But once warmed up it sputters. when i smash on it, the car takes off like a bat out of hell.

I will also reinspect the spark plugs too.

more info idle is perfect, with that ever so slight mis that you can barely hear.

no cel codes either

Coil and cap? Also you said timing is perfect. If the head was decked that's going to affect timing. Are you saying mechanical timing is perfect or have you also checked ignition timing with a light and the diagnostic port jumpered?

Cap n rotor is brand new, mechanical and ignition is spot on

Are you sure the head's the problem. I only say because I was having a misfiring problem recently? Major then very minor. You say there's no blip on your tach when it misfires?

Hey man. Escondido Burrito Eating Professional Representative #420. I live up in the hills of Jesmond Dene. Nice to see a local here!!!

I'm in northern escondido. I just moved here in may. So the blip at idle is not very noticeable on the tac. but when you step on it and it then decides to misfire it's fairly noticeable.

im off el norte, near lincoln...

sounds like ignition timing to me.

iLLson wrote:sounds like ignition timing to me.

2nd

if the car is started dead in the morning, the misfire doesn't come into play until the motor is slightly warm. with that said i don't see how it has to be timing. i am leaning towards fuel supply, or even something like gasket didn't seal on the intake creating a small leak. Once the motor goes over about 3k the misfire goes away...