SR20 Misfire/Backfire

[Zeph331]

Hi guys i have SR20 and had this problem for the longest time i have owned this car. Basically anything above 4000 / 4500+ under /Boost it would misfire.

Sometimes it sound like pew pew coming from under the hood, choking it wouldnt let it go any furthur and sometimes it would do it from the exhaust.
It seems to me like with Ignition breakup / uneven firing sometimes too advance sometimes too retarded? i dunno, would wrong timing do that? thought it wouldnt start the car at all.

And Sometimes it doesnt do misfire at all, Boost fine when its really hot outside


I have done everything from
-TPS Checked and adjusted
-Coolant Temp Sensor
-Clean Air filter
-New O2 Sensor
-Boost Leak checked
-Vacuum Checked
-21hg Vac
-Fuel injectors Cleaned / new o ring
-Walbro Pump
-Map sensor
-Coilpack wrapped in Liquid Electrical tape (Car Runs alot better without stuttering as much, Im thinking if i get new Coilpack this would solve it)
-Timing @ 15* 800-900RPM

[Kingtal0n]

boost leak test,

re-do your timing, the pickup is directional,

plugs/coilpacks good idea to check

basics. tune up.

[Zeph331]

I have power fc installed would the timing procedure be different?

If i do reset the CAS Base timing to 15
is the PFC also affected? If so that means i have to get another tune?

[Kingtal0n]

What I am saying is this,

http://i9.photobucket.com/albums/a90/kingtal0n/Kingtal0ns_240sx_2/P1200499_zpsn7teaftx.jpg (http://s9.photobucket.com/user/kingtal0n/media/Kingtal0ns_240sx_2/P1200499_zpsn7teaftx.jpg.html)

You see how the pickup is oriented? The way it is clipped onto the wire is directional. If you flip the pickup, the timing will read completely wrong, and the CAS will no longer be somewhat center between it's adjustment bolts.

Is your CAS somewhat center?`

If your car runs and drives normal and everything is fine, its just breaking up when you hit 12+ psi of boost (You never mentioned what power or boost) then its just the plug gap. Get some brand new plugs, they dont need to be fancy, and get that gap down around .032" or .028" and the OEM ignition system will be able to keep up with 12+ psi.

[Zeph331]

Usually it starts breaking up under WOT at 10psi on GT2560R.

If i ease into 10psi its fine tho. But around really hot weather i can go WOT no problem

thx for ur help :)

[steve shadows]

Usually it starts breaking up under WOT at 10psi on GT2560R.

If i ease into 10psi its fine tho. But around really hot weather i can go WOT no problem

thx for ur help :)

Sounds like when you hit it hard something is moving around and that causes the break up.

My diagnosis? Coil back harness grounds are shit.

(ps could still be a vacuum leak though...)

Cheers

[Zeph331]

Its true that i have one non bolted coilpack to the head cuz that hole for valve cover is stripped. But i never thought it would be that of a problem

How do i check vacuum? Its reading 550mmhg on the commander