91 240sx ka24de running rich

[yz240sx72]

ok i got a 91 240sx, ka24de it has silva injectors flowmaster exhaust wit 3 inch piping. thats pretty much all the engine work done to it. about 2 months ago i started it up and it idled and was shaking like hell. started driving and it cleared up. last week it started doing it again, but never went away. its running real rich now, so rich a quarter tank lasted 50 miles! it wont take the throttle all thru the rpms. so now its idles around 800 but very shakey and rough. way too rich and sounds like crap. one funny thing is that i drove home yesterday and while cruising at 50 it was running poor, than all of a sudden it just ran like it should, got to the red light and started running like crap. there doesnt seem to be a vacumm leak, cant hear anything funny around the manifold so im pretty sure a sensor went bad. any clues would be helpful.

[rogoman]

You have one or more leaking injectors. To test them, unbolt the fuel rail from the intake manifold and pull off the entire assembly. Keep the fuel hoses still connected and don't remove any individual injectors. Also keep the electrical connectors on the injectors. With the assembly now away from the intake, turn the ignition key to the run position WITHOUT STARTING THE ENGINE. Now observe each injector to look for leaks. There should be no drips.

Make sure you have at least 4 spare insulator rings for the injectors in case some are damaged during rail removal. You can try running some good injection cleaner, like Techron or Redline SL-1, through the system; Give the cleaner about a week or two to do it's job. Then go back and check the injectors again. If still questionable, replace them.

There is also a product called BG products 44K. It is however a very strong cleaner and in some cases it has worsened fuel injection operation; it has a tendency to attack the internal non-metallic parts of a fuel injector.

[vancouverbc]

zerothread/294967 tutorial on taking fuel rail out to test for leaks. I didnt have a problem with damaged insulators, though I did a hack job getting the injectors out and in.