Attn: Misfire Guru's - HELP!

[CRESCENDO]

Here's what were workin with, gentelmen:

S15 SR20DET > RPS13FMICExhDPIntAPEXi Power FC D-Jetro (MAP sensor)9-10psiBOVCAS @ 15 degS15 fuel pump Plug (BKR8E-IX's only 3-4 months old) gaps were at ~ .26Gapped to .30 and problem worsened, so I closed the gap back down.

Here's the issue:

High RPM (5k and above), high load (2/3+ throttle) misfire/sputters.Does NOT sputter at low-mid RPM high load, nor high RPM low load. Mostly at WOT, of course. Tried adding 100 octane to 91 fuel but made no difference.

Am I loosing spark through a component?Where to start?

Regards

[chicos240]

If everything is correct and you are certain there are no idle issues or timing issues, then I would suggest a hotter plug. Like an NGK BKR6EIX

[CRESCENDO]

If everything is correct and you are certain there are no idle issues or timing issues, then I would suggest a hotter plug. Like an NGK BKR6EIX

Do you think that heat range will also be sufficient when increasing the boost pressure to ~14-15psi?

[IanS]

the 6s may be too hot, I run 7s, at 11 to 13 PSI, Plugs doesnt really sound like the problem though I may be wrong, it sounds more like one of your coil packs may be failing, or maybe you have carbon tracks through the coil pack boots, also, make sure your coilpacks are properly bolted down, and the ground wire is in good condition.

[Geno750]

Here's what were workin with, gentelmen:

S15 SR20DET > RPS13FMICExhDPIntAPEXi Power FC D-Jetro (MAP sensor)9-10psiBOVCAS @ 15 degS15 fuel pump Plug (BKR8E-IX's only 3-4 months old) gaps were at ~ .26Gapped to .30 and problem worsened, so I closed the gap back down.

Here's the issue:

High RPM (5k and above), high load (2/3+ throttle) misfire/sputters.Does NOT sputter at low-mid RPM high load, nor high RPM low load. Mostly at WOT, of course. Tried adding 100 octane to 91 fuel but made no difference.

Am I loosing spark through a component?Where to start?

Regards

Do you have a wideband o2 sensor hooked up that you can read off of? If your leaning out then I'm inclined to think it is a dying fuel pump, if its running rich then its probably spark, check ig harness grounds, or like someone else said, spark plugs.

[CRESCENDO]

the 6s may be too hot, I run 7s, at 11 to 13 PSI, Plugs doesnt really sound like the problem though I may be wrong, it sounds more like one of your coil packs may be failing, or maybe you have carbon tracks through the coil pack boots, also, make sure your coilpacks are properly bolted down, and the ground wire is in good condition.

Is there a way to test the coilpacks accurately (since it only happens at high RPM, high load) without replacing them?

How do I clean the carbon build-up, if any?

Colipacks are bolted down firmly.

Which ground wire? From where to where?

Do you have a wideband o2 sensor hooked up that you can read off of? If your leaning out then I'm inclined to think it is a dying fuel pump, if its running rich then its probably spark, check ig harness grounds, or like someone else said, spark plugs.

I don't have a wideband O2. I do have knock readout on the PFC Commander. I know it would help.

Where are my ign harness grounds?

Regards

[IanS]

there is a ground wire that runs from the coil packs, throught the coil pack harness, to the back of the head, it is bolted in.

You can not clean carbon tracks, they happen when spark jumps through the coil pack boot, causing a nice little trail of carbon to be created in the boot, the carbon allows the spark an easier path to ground, causeing more lost spark. get new coil pack boots to fix

[CRESCENDO]

there is a ground wire that runs from the coil packs, throught the coil pack harness, to the back of the head, it is bolted in.

You can not clean carbon tracks, they happen when spark jumps through the coil pack boot, causing a nice little trail of carbon to be created in the boot, the carbon allows the spark an easier path to ground, causeing more lost spark. get new coil pack boots to fix

Ok, so you're just talking about the coilpack wiring, not a seperate external ground.

I would think further grounding of the engine bay wouldn't hurt. Where are the standard grounding points as well as some 'for good measure' points to ground off the engine/chassis?

Is there a way to check for carbon trails?

[tucker3113]

What is the fuel pressure at? Did you check the volume that the pump is putting out? I would look at those things also. Not trying to thread jack but where can you get new boots for sr coils?

[CRESCENDO]

What is the fuel pressure at? Did you check the volume that the pump is putting out? I would look at those things also. Not trying to thread jack but where can you get new boots for sr coils?

Haven't checked the FP yet.

All good on the related question. I'm sure many are curious.

[chicos240]

I soldered all 4 grounds to one thick wire and grounded that wire along with my engine ground on the intake manifold. My idle is much better because of it.I would try the easiest first. Change plugs, change timing. Check your coil packs, good luck checking them at 5000 rpm though. But there is a way to check them in FSM...EC-120 and EC202

[CRESCENDO]

I soldered all 4 grounds to one thick wire and grounded that wire along with my engine ground on the intake manifold. My idle is much better because of it.I would try the easiest first. Change plugs, change timing. Check your coil packs, good luck checking them at 5000 rpm though. But there is a way to check them in FSM...EC-120 and EC202

So where should I have grounds? I do not see any at the moment. I would like to have at least the factory grounds - in addition to others.

I should change timing from factory 15 degrees?

[chicos240]

off the coils there are 3 wires... - + gnd (negative/Positive/Ground) Find the grounds they go to your valve cover. make sure they are well grounded, clean the leads....If you have never messed with your timing, leave it alone. Because you need to set your engine into timing mode because of its variable valve timing, before you can actually check it.

[CRESCENDO]

off the coils there are 3 wires... - + gnd (negative/Positive/Ground) Find the grounds they go to your valve cover. make sure they are well grounded, clean the leads....If you have never messed with your timing, leave it alone. Because you need to set your engine into timing mode because of its variable valve timing, before you can actually check it.

Sorry, I was referring to engine to chassis grounds (i.e. ground wires)

Update: Changed plugs to BKR6EIX - gapped to 0.29A little better from what I can tell so far, but the problem is still there.

On another note, if I increase boost pressure to 13-14 pounds I get what feels like fuel cut. I only know about fuel cut in general but not on my SR - didn't think it existed unless the FP wasn't supporting enough fuel. I've known plenty of SR's with even the stock ecu boosting 14 lbs without fuel cut. The only cut I'm aware of is speed - not in my case, however. Can someone please shed so light/insight?

Regards

[chicos240]

Are you boosting and then you experience loss of power? cause that sounds like boost leak.

[CRESCENDO]

Are you boosting and then you experience loss of power? cause that sounds like boost leak.

I'll boost fine to 10 lbs (aside from that sputter). When I increase boost to 13-14 lbs - that's when I feel it. Feels 'like' fuel cut would - kinda cuts out, car still runs, but if I don't take my foot off the gas right away and get out of high boost, it'll jerk.

[Hijacker]

When the jerking happens, do you hear any pinging or valve rattle? I'm wondering if the power FC doesn't retard for knock. If you're knocking it could be a simple matter of the fuel/air mapping being off. Unfortunately, I'm not familiar with MAP sensors and their setups to put out any guesses as to what could be the culprit.

Does the power FC throw codes like a stock ECU?

[CRESCENDO]

When the jerking happens, do you hear any pinging or valve rattle? I'm wondering if the power FC doesn't retard for knock. If you're knocking it could be a simple matter of the fuel/air mapping being off. Unfortunately, I'm not familiar with MAP sensors and their setups to put out any guesses as to what could be the culprit.

Does the power FC throw codes like a stock ECU?

No. No pinging is heard and no knock is detected through the Power FC either. I believe boost goes down to zero and injector duty cycle does the same at that instant. I'll have to check the procedure for code checking if there's a way. It bucks the same way an un-skilled beginner would drive a manual transmission for the first time - (but we know it's not clutch related).