'91 240sx, strange start up problem

[Equinox]

I am getting an intermittent problem when I start the car. Every now and then when I start the car, it will stumble at idle for about 30 seconds or so. Then the car levels out and after that it runs perfectly. It doesn't happen all the time and I can't figure out exactly what is causing it. Other times the car will fire up, start, and idle perfectly.

I've done all the routine maintenance: new plugs, wires, rotor, cap, and fuel filter. Compression checks out 180psi across the board. And no check engine light. Any ideas??? Thanks.
Modified by Equinox at 9:33 AM 1/15/2005

[s13sr20chris]

does it seem to be running rich at that time? or does it seem to be a misfire? can you make it better by holding the throttle?

[Equinox]

I don't think it's running rich when this happens. I don't smell any fuel inside the passenger compartment. It is misfiring when this happens. The engine and car shake a lot when it happens. Giving it more gas doesn't seem to make it any better, it just misfires more quickly.
Modified by Equinox at 5:10 AM 1/18/2005

[s13sr20chris]

try pulling individual plug wires off at teh time of misfire to figure which cyl is missing. then try wiggling your injector connectors to see if that helps.

[Equinox]

try pulling individual plug wires off at teh time of misfire to figure which cyl is missing. then try wiggling your injector connectors to see if that helps.

Ok when the car is stumbling, #2 cylinder is definitely the one that is misfiring. Wiggling the injector connector doesn't seem to help. I checked the injector connector for corrosion and such, but it is squeaky clean. Any other ideas??

[s13sr20chris]

put a plug on the end of the wire and ground it on the valve cover. does it spark?