misfires... again

well i had it running strong at 18 psi, no problems, now all of a sudden it starts misfiring again under boost. It only does this whenever i try to boost above 14 lbs or so, below that it seems fine. I cant find any boost leaks and i just put in new ngk's. Its a 90 gsx running a 16g with a s-afc and avc-r. fuel system is stock but i dont see how that could be causing it. Im at 5000 ft so i dont think there should be that much of a fuel demand, even above 14 or 15 lbs. Ive got the avc showing injector rate and they arent even close to maxing out. I guess it could be the pump, but it doesnt feel really feel like fuel cut, but there is major power loss. I got spanked by a stock wrx while i was running 18 lbs because of this wierd problem. Anybody have any ideas whats going on?

I see the part where you say you replaced the plugs (wise move), but I dont see the part where you tell us what you gapped them to ;) They usually come too big. If you didnt already, set the gap to .028 and tell me if it doesnt fix it. If that doesnt do it, plug wires are next. I forget what you said you did already though from the other thread.

ive got them at .3 now, but ill try to get it closer to .28, maybe even a little smaller and see if that helps. Dont see how it could be the wires, they were working fine under 18 lbs before... but i guess it could be them. I dont I cant really think of much else that would be causing it. Before I had a pretty bad leak, fixed that. I checked again for leaks and havent found anything. when it was leaking it was missing under any kind of boost, now its just around 14+ lbs.

Hmm. .3 should be ok. Never rule out the wire just because they were workign before, expecially if they are not stock or NGK. BOost leaks will certainly do it. Have you built an intake leak tester yet?

Hmm. .3 should be ok. Never rule out the wire just because they were workign before, expecially if they are not stock or NGK. BOost leaks will certainly do it. Have you built an intake leak tester yet?

misfires...is when your engine starts boggin at high rpm rite?
i think im in the same situation...i replaced my spark plugs aready...and it still does the same thing...could it be the spark plug wires?

intake leak tester?

I replaced my BOV and my car started to misfire on the high end. Changed the plugs and it was fine for a few days. The on the high end the car would miss again. Changed plugs again, made double sure of gap. Raced for a few weekends, no prob. I over revved my engine off the line (tranny slipped into neutral). For some reason the miss came back after that. The plugs looked fine and I had Taylor wires....which are supposed to be good wires. Those things were crap, switched to Magnecores had no problem since. I'm running bpr6's with light mods, when they burn out I'll switch to 7's. Also make sure your spark plug wells are clean, DSM's have this problem with oild and water in the wells.

misfires...is when your engine starts boggin at high rpm rite?
i think im in the same situation...i replaced my spark plugs aready...and it still does the same thing...could it be the spark plug wires?

intake leak tester?

Bogging and misfiring are among the most incorrectly used words these, days, so here is a quick explanation. Misfiring describes the plug not firing, for many reasons. It can misfire at idle or at high rpm, there is no descrimination. Some people use the term "high end miss" to describe a high rpm misfire, etc. Bogging is comes from the old carburator days when you would floor the gas and the car would hesitate for a minute before it went. Either from too much or too little fuel when the pedal is floored. In an AWD an example is when you launch at too low an rpm and the motor gets pulled down to low rpm, loses boost, and has to slowly pull back up to an rpm where it can clear its throat and make some power. There's really no such thing as a "high rpm bog." It has a similar effect, but its more like a stutter or stumble depending on whats going on.

To answer the second part of your question, it could easily be wires. The wires are at fault almost as often as the plugs, especially if they are not stock or NGK as I mentioned above, or they are old. Some poeple swear by magnecores but I've had sets fail within 24 hours. After 3 bad sets I gave up and stayed with stock wires. I've also used NGKs briefly with great results, and most of my friends use them. They're cheap too. 50-60 bucks. And also make sure you dont overlook correctly gapping the plug. This is very very important, and overlooked by many DSMers. I'll pull my plugs 3-5 times in between changes to make sure the gap hasnt changed. ;) .028 to .030 for most poeple, .026 to .028 for 25 psi and up. The general rule though is to run the largest gap that wont misfire on your car...

I checked the gapping, ok there. Ill change the wires whenever i get a chance. Ive been sick all weekend so i havent really done much. Ill let you guys know if the wires make any difference.

Why are you guys always right? :) Changed the plug wires, cranked it back up to 18 lbs, runs like a charm. I did find an exhaust leak where one of my head studs broke though. Guess that gives me an excuse to get a port and polished head, if i can find the money. Anyways, thanks for the help AGAIN. Im new to the whole turbocharger scene. But cant complain so far. And now i know boost leak is very bad and dsms are picky when it comes getting a good spark.

Oh, and my brother just got a 92 stealth r/t turbo, time to show him how my 4 banger can woop all over his fancy twin turbo sixer.

Why are you guys always right? :)


cause it has either happend to one of us or its a common thing to check for certain problems!!! :iceslolan