Misfiring

[Ligouri Rd]

Well I have been breaking in my KA-T for a few months now and have a persistent misfiring issue. When at idle or light throttle the car surges slightly , like one cylinder is dropping off. Plus im getting a missfire code (duh) and gun-shot-like backfire when decelerating in gear. When I try to accelerate there is a also lag for a few seconds right off of idle then power comes on strong. The boost/vac does not change while this is happening so I do not believe it to be turbo lag.

Each time I pull the plugs cylinder three is way rich (black). After speaking with a technician at Garage Kwai, he suggested that the problem may lie with the ignition system. I confirmed this with a timing light on cylinder three and observed the light blinking intermittently to not at all at idle. If I rev the engine fast the light blinks normally but starts blinking intermittently after returning to idle. I tried swapping the distributor with the one from my '96 KA. After warm up, I still had the same problem. So I swapped caps back, which resulted in the same problem.

Origonally I was told that this was most likely due to a leaky injector, so I did the injector drop test and #3 has no change in roughness when that injector is unplugged. Which makes sense to me since if there is fuel going to that cylinder it is not being ignited anyway.

So I ask yall, does the problem lie with the ignition (New distributor to the tune of $500) or is the injector pissing so much fuel out the rail that it is fouling the plugs and not causing it to fire? Each time I pull the plugs I clean em with a wire brush to get rid of the carbon crap.

By the way I have new plugs (BKR7E gapped to 32) and new wires. The injectors are nissan 370cc/min cleaned and inspected by RC Engineering.For reference here is my previous post and complete setup: http://www.ka-t.org/forums/viewtopic.php?t=4249

[C-Kwik]

Did you check the plug wires? It's not uncommon for a plug wire to break internally or even externally and cause a miss. I had a similar problem when I had first put a turbo on a KA and it started missing. While inspecting it, I found the problem when I placed my hand on the inlet tube and got a small jolt of electricity. Lucky for me, it was buffered by some other parts. In any case, I discovered a small tear in the shielding that allowed the spark to jump out to the intake tubing.

And if this is the problem, I suggest staying away from the cheap auto parts store brands. I've lost several sets when the terminal decided to stay attached to the plug and not the wire when I went to change out the plugs. OEM wires never had this problem. Quality aftermarket sets may be fine too, but personally, I'll stick with a factory wire unless I really need to upgrade.

[AmoebAssassin]

+1 on the plug wires idea, also check that your plugs are gapped properly, improperly gapped plugs will give you weak spark and lazy/intermittent combustion.

[Ligouri Rd]

I tried swapping plug wires back and forth a few times to see if that would help to no avail. By Quote »(BKR7E gapped to 32)[/quote] I meant that I checked the gap and it was set to .032.

Anyway, I spent 50 bucks on a new cap and rotor, with no improvement. Oh well not a bad investment anyway.

I pulled the #3 spark plug and cranked the motor while a buddy (thanks Z16a) held the plug to ground. Outside of the motor it sparked fine.I pulled the number three injector and sure enough there was a slight nick in the o-ring. A new o-ring later and she was running fine, beautiful in fact. Dang, all this trouble (IAC, ignition, etc.) all cause of a stupid o-ring.I thought the idling issue was due to the lightweight flywheel. I feel so much better now that she's running properly.

I took her out for a spin and finally opened her up to full throttle for a few moments. Now I have some issues with boost creep...but I'll save that for another post. Thanks all.