Well, among other work, like changing out the turbine gasket and manifold gasket... we also replaced the NGK's w/ some lightly-used HKS plugs. the plugs looked almost brand-new. they had only been idled on before. we put the car together, all connectors and vacc lines hooked up (including the MAP and TPS). start the car, and it misfires horribly. it runs ridiculously rich and stumbles badly when you crack the throttle. holding the throttle at 25% causes the motor to stumble and then wants to choke out.

its got a Jacobs amp on it w/ an FC leading coil. newer NGK wires also.

before the plug change, i had the car idling (roughly) at high 13.xx : 1 AFR's, cruise was also mid to high 13's as well, on the stock 550 primaries. after 0psi and boost map, it goes down to 10:1 and richer. i attributed the poor part-throttle and idle quality to the old, fouled NGK's. the new HKS plugs should have fixed this. i know the Tune doesnt change, so its something physical. i think the coils are still on the original sub-harnesses. but its unusual that the car would start acting like this after a simple plug change.

the PFC injector M/S readings are between 4-5ms at idle, just like everyone else who is running stock primaries.

dont say "make sure the map is connected" and dont say "calibrate the TPS". the MAP is connected and the TPS is recalibrated on the PFC.

 

What is the gap on the HKS plugs? I wouldn't use anything with a larger gap than the stock plugs. Have you tried a new set of stock plugs?

I'd also recommend that you double-check everything. It's possible that you missed a (ground) connector somewhere.

-s-

 

the HKS plugs havent been gapped. i was told they are iridium and are not supposed to be gapped. we are going to try another trailing coil and new NGK 9's tomm. the only ground that ever gets in the way is the sheilding on the subharness. thats installed and i have an 8gauge ground going from the coil pack chassis to the block.

ive also tested the subharness and then the engine harness between the ignitor and the coils. the igniter has also been swapped out.

i hope the new plugs and coil fixes this.

 

all i can say is that the HKS plugs are crap. Probably a bad plug. This has happend to me a few times. On plugs that have been sligthly used.

JT

 

Just a suggestion,but check that all the plug wires are going to the right plugs.
If not thats the problem you get open the throttle a bit and it will start misfiring
etc.Happened to me once with the symptoms you mentioned.

 

yeah, well the trailing coils have wires going to the TOP plugs, and the leading coils have wires going to the BOTTOM plugs. i hope thats right...

JT, hearing about your HKS plug failures kinda gives me somehope. these plugs are slightly used, the car it was in was started and idled but thats about it. i dont think they were ever really driven on.

we are going to try the old NGK's we pulled out to see if it changes Anything.

 

Try to make only 1 mod at a time. It will make diagnosis of problems, a lot easier.

 

we changed back to the NGK 9's on trailing and leading. i also wired up an FC trailing coil and that fixed everything. we just made a 200 mile road trip today. i tuned just about all of the vaccum fuel map under 4000rpm. we got 200 miles on 2/3's tank. car runs great now

thanks guys