missing at high RPM

[burninator]

I took the Z to it's first autocross yesterday (first real chance to drive it anywhere at all) and it seems to be missing and popping at high RPM (hard to say how high, I don't get much chance to look down at the tach).

 

There is actually a video of it up on YouTube and you should be able to hear it:

I know my performance wasn't great on that run, but I'm having some issues with the suspension that I'm working on (its very tail happy, but that's an issue for another thread). In case your wondering I have a 6 into 1 header and an MSA aluminized exhaust.

 

The power goes all to crap, and there is some black smoke. The black smoke indicates that it's rich, but I'm assuming the it's rich because it's missing. It doesn't seem to do this in neutral just by revving it up.

 

I have an L24 with stock everything, but the plugs, wires, contact breaker, cap, and rotor are new. When I changed out the contact I adjusted the gap, so I'm sure that's correct. I believe there is also a dwell adjustment and I should be able to get a gauge to measure that and see if it's in spec. Could that cause this issue?

 

I'm going to pull the spark plugs tonight and have a look at them.

 

Any suggestions?

[burninator]

No one yet?

 

It's been less than a day so I'm probly not being patient enough. I didn't get a chance to do much to it last night, but if I need to order a part (sometimes takes a couple days for our NAPA to get parts from the warehouse) I would like to get a chance to find it before the next event this weekend.

 

I was also wondering if an ignition coil going bad might cause a problem like this. I know I need to replace my alternator, but my battery was fully charged when this problem started. If I'm right, a fully charged battery will be at 12 - 12.5 Volts and the alternator running should up that to about 14.5 Volts. I don't know if having a slightly low voltage from a weak alternator could cause my problem.

 

Just trying to provide as much info as possible hoping to get some advice from someone smarter than me. Thanks in advance.

[burninator]

I installed a different alternator and I'm getting plenty of voltage off of that now. Problem still exists. I verified that it does do it in neutral and won't rev past about 5000 rpm. Checked all the spark plugs and only one was slightly sooty.

[burninator]

In case anybody is following this: I borrowed a coil from a friend with a Z and it ran much better. I think I'm going to pick up a new coil at the store tomarrow. That should do the trick, I'll post back if something comes up.

[burninator]

Put in the new coil, didn't fix it. Checked plug gaps and mine were at 0.035 regapped to 0.040 and it runs better. Still doesn't seem rev all the way up. Would there be any kind of rev limiter on this car? It gets to about 6.5 and that's it. Probly high enough, I'm just curious if it should rev higher. Still haven't checked the dwell, but I may do that tonight if I can gain access to a gauge.

[FlatBlack]

I was on the interstate and was getting lean a little under 6000, I figured it was somewhat normal due to my stock EFI. Yours is a carbd L24 though, right?

 

If your plugs are white then you're running lean but you said up there that they were 'sooty'

[burninator]

Yeah, most of the plugs were normal brown color 1 or 2 had a decent amount of carbon on them. When it's missing it's running rich (I believe this is because of the miss not the cause of it).

[Sean 71]

What was the outcome of the missing at high rpms?

[burninator]

I don't recall what exactly fixed it. It stopped running at all a while later. We regapped the contact breaker (they go out of adjustment faster than I'd have guessed) and replaced all the plugs with a hotter plug and that did it.