sr20det black top missing under load.

[scott.davey]

hey all

my sr20det black top started running flat on boost a few weeks ago. then it started missing when you hit boost
around 3000rpm and will miss the whole way out.
it is missing when its idling sometimes aswel. dont know if its related?

i have done a self diagnosis test and got knock sensor.
ive replaced that and its still missing.
i have also tried new coils and it still missed.
i can unplug my air flow meter and it will still run fine.

any ideas?

[rcdad123]

have you checked the plugs, fuel filter, fuel pump, etc.

[scott.davey]

I had a visual insection of the plugs and they look good. I dydnt think it would be fuel filter or pump because it backfires between gears aswel.

[rcdad123]

check pipe between maf sensor and turbo inlet. and make sure the knock sensor code is gone. if it`s still there, check for bad knock sensor wiring

[scott.davey]

No splits in the pipe between maf and turbo. Checked the intercooler pipe connections and couldn't see any splits. Knock sensor code isn't coming up anymore.

[rcdad123]

check for engine harness ground. i had a 22r turbo that had a loose engine harness ground that would loose power under boost and misfire a lot. turned out that i forgot to tighten the ground on the intake manifold after i did a head gasket replacement.

[scott.davey]

Oh true. My motor has got so many groundong wires. I'll go through them tomorow and get back to you

[KiLLeR2001]

Check fuel pressure. Stock is 37psi with vacuum plugged in and 43psi without. Stock spark plug gap is 0.036" you might want to lower it to 0.030" or 0.028". Make sure timing is 15*BTDC.

[scott.davey]

Checked all earthing wires and they are fine. I'll have to get a pressure gauge and timing light killer2001. I'll try suss it tomorrow and see how it goes

[Mikester]

If you ever used octane booster, forget everything said above and change your plugs. After using it, the plugs will look okay; but will absolutely be ruined. There are no exceptions to this... SR/RB + octane booster = cooked plugs.

If that's not the case, I'd change them anyway and go from there. Also, check all of your IC piping & boost lines...

All else fails, check timing & fuel pressure as stated above.

[codyace]

So it misfires under load, but free-rev's in nuetral or out of gear just fine?

Check plugs, and check for a major vacuum leak.

[scott.davey]

Just put a set or.bkr7e spark.plugs in and a new fuel filter. Problem fixed. Spark plugs looked fine last time I checked.
This time one broke as I was taking it out so I guess even tho something looks good doesn't mean that it is.

Cheers for the help everyone

[codyace]

Good to hear man! Under load misfire is almost *always* spark or vacuum.