Can spark/no spark cause a lean condition?

[dtowngoalie]

I'm having trouble tracking down a random missfire at idle. At WOT and cruise the car is fine, but at idle the car breaks up rather bad after being run for a while.

When I first fire her up she idle good for about 10 minutes, then it begins to miss a little bit. But after I take it for a drive at heavy load and then lets say I come to a stop light, it breaks up really really really bad at idle. the wideband reads like 17.0.

I got bored one night so i decided to unplug a coil pack while the car was idle, of course it made it miss, but I thought it would make the wideband read richer because of unburnt fuel, but it reads leaner when no spark occurs. My question for you guys is can having bad plugs/ coils make the car appear to be lean?

[Cjmartz2k]

Counter intuitive, I know, but a miss will make it read lean. Along with unburnt fuel, there is an even larger proportion of un-burnt 02 when it misses.

[dtowngoalie]

Couldn't have asked for a better response. Now I just have to figure out if it's missing because it's too lean, or missing because of spark. Could it be cause my coil packs are old and after getting very hot (continued driving) they aren't working very well. The car pulls good vaccuum and fpr is 39-40 psi at idle. Might try to swap spark plugs and see if that helps. Any other ideas are appreciated.

[Darius]

Search for the coil pack debate thread. There's lots of good discussion there.

If it is missing at idle, it definitely misses under load. It is probably the coils, but could also be the ignitor if you have an S1 RB25

[dtowngoalie]

I really don't think it missed under load, but it could be that I'm just not hearing it. I have a rb20, but I have swapped igniters and that doesnt help, gonna try the coils also.