1989 240sx: Motor shakes

[BlackHat]

I'm reposting this under a new title that is more searchable than the last. I thought I had this problem fixed, but it's still happening.

After the car has warmed up, the engine/drivetrain shakes when starting off in first. Due to previous advice I have checked timing, which was off. It was running 9* advance at idle. I corrected it so that now it runs at 15* advance at a much steadier idle of 750rpm (was idling either 550rpm or 850rpm before the adjustment). That has helped some, but apparantly not enough.

Other, possibly applicable, changes that have been made right before this all started happening. I had changed out the clutch to a slightly more performance clutch, removed the egr and aiv systems, and ran into an electrical problem that killed my horn/cruise control/A/C/cig. lighter (Maybe it also got a sensor?). The electrical problem was interesting and I'm still not sure what caused it. I was drilling holes so I could mount the amps for my stereo system and hadn't disconnected the battery. I didn't think it was a problem because I was done with wiring. The horn just started going off with no key in the ignition. After that the other electrical devices were killed too. Guess I learned a lesson about disconnecting the battery no matter what (I'll probably do it everytime I change tires now too

That's all that I can think of that may have ANYTHING to do with the problem (and some things I'm sure that don't).

[180fan]

you check the injectors?

[BlackHat]

No, but you did remind me that I did check the spark plugs. I unplugged them one at a time and each one, when removed, made the engine run rough.

How do I check injectors?

[navysnail]

use a noid light to make sure each one is getting a signal. listen to each one, you should hear them clicking as they open and close. you can also hook up a fuel pressure gauge to the fuel system and pressurize it. then, allow the car to sit and observe weather or not the gauge drops quickly to 0 or not.