Misfire Coming On Boost

[No Crust Racing]

Hey guys, Here's the story. S13, CA18, T25G, 14psi, Iridium spark plugs gapped to .7

If I drive along in second at about 2800rpm and drop the throttle flat (or if I happen to drop back from 3rd to 2nd and flatten the throttle, the car will mis and splutter from around 2800-3000 rpm up til as late as 32-3400 rpm.

This is much more prevalent when the car is fully up to temp.

I've tried swapping in different coil packs, cleaning the electrodes on the coil packs (no cracks on the existing or addition tested coil packs. Putting fuel into the map there (SAFC) taking fuel out of the map there. Swapped over the coil pack loom.

Plugs are a heat range 6 so a range colder than factory and are only 3000-3500 ks old, about 1000-1500 of those would be track ks. The plug shows white discolouration that correlates to the high rpm usage (this is a track car).

What are your thoughts? I'm thinking of grabbing a cheap set of plugs today to test, but the iridiums were $25 each and are only 3500ks old, the car only makes 165rwkw.

Initially I thought coilpacks or tuning but after trying two sets of coils and putting all the fuel in and taking all the fuel out it doesn't seem to help.

[Nisme]

Something probably really anoying like; a vacuum leak or a seal somewhere.

Try letting the car idle and listen for air hissing or maybe even trysoap to watch for any bubbles. Also try this maybe with a friend leave it nuetral and rev to build-up pressure.

If not this maybe an oil pick-up issue????

Do you have an aftermarket CPU, get it dynoed...

Good Luck

[No Crust Racing]

Im thinking that if it was an air leak then the problem is it's too rich and I took all the fuel out of the map to test and it made no difference.

Car has been on the dyno an has a tuned ecu, I have the safc to monitor and make small ajustments

[paulr33]

when did the problem start

has it ever worked - ie no misfire on boost

whats changed recently

[STATUS]

try 0.5mm gap, if we are required to use them we run all our iridium and plats @ .05mm without power loss.

[DVS JEZ]

Try cheap copper plugs at .8mm

[No Crust Racing]

New plugs gapped to .65 and fresh fuel, still doing it. The fuel filter is only 1000ks old as I considered that.

I'm going to do a bit more testing with the tune as it "feels" like mix related, though I did consider timing?

[STATUS]

Try cheap copper plugs at .8mm

coppers @ 0.8mm are equiv to irridiums @ 0.5mm.

[GTScotT]

try 0.5mm gap, if we are required to use them we run all our iridium and plats @ .05mm without power loss.

This.

Had one of these motors at 20+ psi with a disco and could only ever do it at 0.6mm or smaller.

SR eater.

[GTScotT]

New plugs gapped to .65 and fresh fuel, still doing it. The fuel filter is only 1000ks old as I considered that.

I'm going to do a bit more testing with the tune as it "feels" like mix related, though I did consider timing?

Sorry missed your prior reply.

As a test try crimp your fuel return hose after the FPR. If it works then its your FPR.

[No Crust Racing]

I'll gap the plugs smaller and try again.

Curious as to how the fpr test works?

[DVS JEZ]

Have u replaced the fuel pump? Might be as simple as needing a 2nd hand gtr pump in there.

RRR

[DVS JEZ]

coppers @ 0.8mm are equiv to irridiums @ 0.5mm.

Ahh k fair enough.

[Rolls]

Have u replaced the fuel pump? Might be as simple as needing a 2nd hand gtr pump in there.

RRR

Would never replace with second hand personally, even if its known to be good.

[No Crust Racing]

Ok re-gapped plugs to .5 noticed that the new plugs are already quite black with carbon , not fuel or oil, a dry build up. Interesting given they are only 50ks old.

Will test drive when the road is dry again, too hard to test in the wet.

[No Crust Racing]

Ok weather is finally good enough to go test at .5 will do after work.

Anyone care to explain how crimping the fuel reg hose will help me test?

[DVS JEZ]

how did it go??????

[Cowboy1600]

Ok weather is finally good enough to go test at .5 will do after work.

Anyone care to explain how crimping the fuel reg hose will help me test?

Whether the FPR is busted and not holding pressure up to your injectors. Crimping will increase fuel pressure to the rail if there isn't enough now.

[No Crust Racing]

Sitting on the couch watching the new Top Gear don't think I'm getting to it tonight. Will update shortly.

[No Crust Racing]

Ok felt guilty so went for a drive and skipped the last bit of top gear!

A few things to note. Gaps were .5 and I also noticed a plug on top of the air regulator under the throttle body had come off so I fixed that.

Went for a drive and it was only right at the end of the drive that it started to miss a small amount and bog down if I flattened it from 25-2800 onwards. I think it was too cold last night as normally when it does it the water temp has come up to 70 and it only got to 60 last night as it was late and quite cold. Water temp sender is in the rad return hose FYI.

I noticed too that when the car is warmed right up and starts missing it also appears to rev up slower. Wondering if this could be a electrical issue with the cas. I'll take a look at the service manual for the testing procedure and will test the crimped fuel reg next as I only wanted to test one thing at a time.