ever since we did the longtubes and yp ipe on my car back in february of 04 the car has had a slight miss from time to time..it put down 291/324 with just afew bolt ons and ran a strong 8.3 at 85...now this last decdember we ported the heads and installed 1.6 roller rockers and springs..we have pretty much figured out how to make the misfire happen..if you driveb the car..then shut it off and let it sit for about 15 minutes and then start it back up it will miss..like not just a little miss../the car will run like complete crap..like sputter and rev up to like 3-3500..but if you hit WOT it seems to clear up until you let off..also the symptoms go away after about 5 minutes of driving..it also put down a disappoting 291/324 (exact same numbers) with the ported heads and rockers..we have replaced the opti..the plugs and wires..gaskets..even the injectors..the miss is still there..however last night we disconnected the O2s..we let the car sit and so far so good..the SES light pops on after you drive the car for about 5-10 minutes but there is no miss..could bad O2s really explain big power loss and such a strange miss?

 

ttt

 

so you guys reply to every other thread about a misfire but not this one? little help here

 

While back I had a miss-fire on my Z that had me really frustrated because it did not do it all the time, checked all the usual things (fuel pressure, sensor readings, wires arching, noid light on injector connnectors) and found nothing.
Had new opti, plugs, wires, O2's and fuel filter. Went to Auto Zone and priced a set of plug wires even though mine were fairly new AC Delcos. The Auto Zone wires were $25.00. I figured for that price its worth buying a set to see what happens, put the wires on my car and fixed it.
Thats the story on my mystery miss-fire, hope you find yours soon.

 

Really check out your fuel system; pressure on and off, fuel filter, and regulator. I didn't see if you had a tune after the header install because you do need to richen things up after that. A lean condition could be the culprit.

 

I have had a slight misfire two times and both times it was plug wires. The car started eating them right after a header install even though they are as far away from the headers as possible and the second set got boot protectors as well. Haven't gotten more than 6 months from a set since the headers went on. Went with high temp Accels with boot protectors this time and hoping for the best.