Car sputters at random psi

[240KAT]

Any boost above 7psi, and my car will sputter. It'll rev smoothly to, maybe 10psi, them fall. It goes something like "vrRRRRRRRR (smooth) then GRRRRRRRR". I had HKS spark plugs in there and checked them, and two were gapped to .038!. I regapped them to .028-.030 (it was in a parking lot). So i ordered some NGK Iridium plugs and they're gapped to .028. Problem still occurs. However: sometimes it'll hold as high as 15.6psi in 5th gear. Its very odd and I'm getting irritated. Any thoughts? Could my timing have gotten fawked up racing at the track or something? I thought once timing was good, it was set. At the track, one of the spark plugs (old ones) broke. As in, the porcelin (sp?) part broke from the 3/8" fitting. I figured it may have just overheated. Im stumped..and this is getting bumped till its fixed ;)

[ItzGenX]

It sounds like ignition breakup. My SR20 had the same problem, and it turned out to be some weak coilpacks. I replaced them with Splitfire ones. Although you have a different motor (by your username you have a kat?), it uses the same concept. Your coil is probably becoming weak or not being able to get the most of its power to the plugs. Try checking rotor, rotor cap, spark plug wires, and grounds. If that doesn't solve it, either get a new coil or upgrade to an msd or something. If indeed you have an SR, the coilpacks are probably the culprit as they are a hit and miss thing. Mine missed at 5psi and higher.

[240KAT]

hmm..that makes more sense. Someone else suggested it was a boost leak. I went driving it and i can hear the bov extra loud..like lots of air blowing through it (during heavy acceleration) Perhaps a loose spring (I have the SSQV) Is there a way to check the coil plug things?






I do have an SR..check sig. ;)

[ItzGenX]

I never really checked mine. I just knew it was the problem because changing gaps would cause a difference in how it ran slightly. I also knew because I could run the car at full advance but not at stock timing. The reason I knew when I had to advance it was because the spark fired earlier during less cylinder pressure. For some reason the problem didn't occur as often with the motor at 22+ degrees advanced (don't go over 7psi, it was just a test). Then I retarded my ignition down to about 18, and the damn thing couldn't accel for crap (pop pop pop brapp puff). When ignition is retarded, the spark fires while the cylinder pressures are already kind of high. Ever since I changed my coilpacks out, I never saw the problem again! (nothing else was tampered with)

As for your BOV, I think the SSQV resists leaking due to its valve design. It uses boost to hold the valves shut. The only way it would leak is to be absolutely faulty or not on tight.

Try the advance trick and run it through the gears and see if it resists the problem. Advance it very little at a time. If it is indeed your coilpacks having low energy, then the problem would go away little by little the more you advance your timing. Also, check your grounds, try new ground locations before doing anything. A bad ground could cause weak sparks too.

[240KAT]

well, i drove it some more and decided to ride the grr noise out for a minute, the boost held, so its not my turbo wastegate or anything (i have a digital boost meter, it held to the tenth.) So it's either the ignitor or the coil. I'm sure its not the ignitor because it only has 35,000 miles on it :loco: It does sound like an ignition/timing issue, but im sure it's not the timing because i didnt adjust timing during engine install out of my clip, nor have i had this issue until now. I think I'll try and get the Splitfire system. How do you like yours? Did you notice any hp gains?

[mellojoe]

what plugs are you using?

On higher boost levels you may be blowing out the spark. You may need to go a range colder to prevent that.

[uiuc240]

have you ruled out a slight boost leak? just because it makes pressure doesn't mean it's not leaking...

Eric

[240KAT]

i just put in NGK Iridiums heat range 6 (im pretty sure).

I'm pretty sure its not vacuum..the only place I could find anything like that was in my bov. I had it set way loose from when i first bought it and around 8-9psi, i could hear air screaming through it..i tightened it up and no i just dont have a screaming loud bov at 8-9psi..car still falls. I ordered a new coil from jgy for $35 and ill test each coil. It's only 1 cylinder thats dropping..so maybe i burnt one the coils or something from racing it so much on track day (8 passes in 3~ hours). If that doesnt help, I have a spare ignitor ill try out. If all these fail, car will be in f/s section lol.