I have been misfiring in the upper rpms/full boost area of my powerband. But ti only does it after the car has been driven for awhile. I can a quick pull a little after I start the car and everything is good, but after 10-20 mins it gets worse, and only gets worse as I drive.

The plugs are gapped at .030, using ngk blue plug wires. I recently replaced the coil from a spare distributor I had laying around. The one in there was kind of bent I guess you'd say. The new coil did not help.

Is there anything else I should look into. The car is on a basemap but was running fine 2 weeks ago. The only thing I can remember changing is wiring up vtec.

Any help/advice is appreciated.

-Eric

 

well basemap boosting isnt really the greatest as to most of us, and usually the owner really has no idea of what thier timing numbers really are.

but my misfire problems usually came from a plug gap being too large, drop it down to .028 and see if it makes a difference

do you have a wideband in the car? are you sure its spark tho?

 

how old are the plugs?
my car is doing something similar, had it tuned for the methanol injection and cut out open. tune went fine about a month ago and nothing had changed. last few days it misses in the upper rpm just like your too. won't rev past 7000 while missing either.

 

No, no wideband. The car runs great except the misfire issue, and its not even as severe as the cases iv been reading.

When it does happen it is like an inconsistent rise in rpms, and makes a noise that sounds like the engine didnt fire and then continues on.

I believe the timing was pulled .5 or .75 degree per lb. I need a timing gun to set the engine timing, but as of right now it is retarded at the distributor also.

I just figured a .028 gap could be too small so I left it at 30. I will definately try lowering the plug gap later on though.

It is on a z6 if it matters.

 

mine sounds like im hittin the rev limiter way soon, and i know it isn't.

 

.028 is not very small considering what we do to our motors! my gap is .020.

also what are the plugs?

and if you are pulling timing in the map, and your distributor is retarded is the timing is probably too little which will cause the same issue as too much,

 

had similar issues. This is what we did

replaced the ICM
Replaced the coil
replaced the sparkplug wires
reduced the gap to like 24-26
checked and rechecked the sparkplusg to make sure they were not broken or fouled.

The last one is way important as we changed the entire DIzzy for a new one and the problem came back like 3 days later. Scratching our heads and ready to commit suicide we realized one of the plugs ceramic surface was cracked and that solved the problems. Good luck

 

Yeah i think im going to give the plugs a once over when I get the chance.
Also I know when it is going to misfire, because the idle surges. When it runs good it idles like a dream at 500-600rpms.

Where is Apopka? If it is on the west side you ever go to the bradenton/tampa racing track events?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mrbsponge &raquo;</TD></TR><TR><TD CLASS="quote">.028 is not very small considering what we do to our motors! my gap is .020.

also what are the plugs?

and if you are pulling timing in the map, and your distributor is retarded is the timing is probably too little which will cause the same issue as too much,</TD></TR></TABLE>

They are brk7e's which is 2 heat ranges colder than stock. If the timing is as bad as you say it might be, the first thing im going to do is set the timing correct @ 16 degrees.

 

why are you even pushing it into the high rpms on a basemap? if you're misfiring, it's most likely an ignition problem. it could be the timing on the basemap......

 

I barely go into boost, and if I do it is in 1st and 2nd where load is low. Its only when I fix something and see if I still get misfire in 2nd or 3rd.

It is not a severe misfire, just something I want to iron out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mrbsponge &raquo;</TD></TR><TR><TD CLASS="quote">.028 is not very small considering what we do to our motors! my gap is .020.

also what are the plugs?

and if you are pulling timing in the map, and your distributor is retarded is the timing is probably too little which will cause the same issue as too much,</TD></TR></TABLE>

as is my gap as well. 0.020

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Vtaaak y0 &raquo;</TD></TR><TR><TD CLASS="quote">I barely go into boost, and if I do it is in 1st and 2nd where load is low. Its only when I fix something and see if I still get misfire in 2nd or 3rd.

It is not a severe misfire, just something I want to iron out.</TD></TR></TABLE>

base maps are to get you to the dyno.
goin out and doin pulls to see what you are replacing if it fixes it isnt a good idea.
get it on a dyno, see where the timming is on the ign table, look at your a/f since you have no real idea where it is and go from there. i had an ignition breakup on our dyno, turns out i am making power to necessitate 8's. john from ngk told me to run 2668's. they are iridium. how much power are you making or duh you havent gone on the dyno yet.

get on the rollers and see whats up, stop boosting on a base map before you thrash the engine that you have spent all your hard earned money on.

 

I am running 6psi on a bone stock z6, I do not see how it can be compared to a 520whp b-series.

Although I do agree on you with the tuning I do not feel it is as important as you think, my car runs strong and barely misfires when it does. I know with a proper tune the car would be a world of a difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Vtaaak y0 &raquo;</TD></TR><TR><TD CLASS="quote">I am running 6psi on a bone stock z6, I do not see how it can be compared to a 520whp b-series.

Although I do agree on you with the tuning I do not feel it is as important as you think, my car runs strong and barely misfires when it does. I know with a proper tune the car would be a world of a difference.

</TD></TR></TABLE>

you just answered your question...i am not trying to bust *****, but ^^^

 

Yeah I appreciate the info and im not taking any of this to heart.

By a world of a difference I meant power wise. Im not worried about blowing the motor the way it is running at all.

And I know that without tuning I can get it running proper without misfires. Although it may be slower it will be a smooth powerband like it once was.

I know tuning is part of the problem, but I know the problem doesnt lie in the tune. Know what im getting at?

Thanks for the help so far everyone, never hurts to get an opinion.

 

Swap in some new plugs and wires--Drintegra was talking about my car and that sh*t was ridiculous. I have mine (Bkr7e) gapped down to .26 with stock dizzy, stock wires (not even NGKs) no problems since. Let us know what happens, good luck