j30 won't start, need help

[mobilefleet]

bought a 94 J30 that had sat for about 6 months. Previous owner said car had started running rough/stalling so he parked it and got another car. I bought the car, checked compression (180 or so on all cyl.), spark was great, but then discovered that 3 of 6 plugs were not wet with fuel, so figured those were clogged. Knew it was a big job changing injectors but got it done using dremel method. BEFORE I did any of this, checked ECM and it had no codes. After work was done, car started but ran very low idle, about 400-500 RPM, and if you give it gas it popped and backfired pretty hard (I observed the air intake shake as it backfired, apparently through this and not the exhaust). I got it to where it would rev to about 5-6000 RPM but it was still rough. Now it will not start at all. Check engine light had come on after backfiring and I got codes 34 and 51 for knock sensor and injector analysis, whatever that means. I also put fresh premium fuel in the tank. Can the knock sensor keep it from starting? Any other ideas? It acts like it wants to start but won't light off and run. It's getting frustrating. I wouldn't think the knock sensor would keep it from running but maybe so?

[GerryO]

Did you check the resistance reading of all six injectors? At 172K one of mine failed due to an open coil (infinite resistance) and not due to clogging.

How about checking/cleaning the MAF, and checking the EGR valve functions and the timing? How many miles on the car and when was the timing belt last replaced?

[driverdriver]

Ohm test your injectors. They should be within 10-14 ohms, anything below or above and your injectors are toast. Also check your ignition coils.

[mobilefleet]

all test good with ohm test. I'm starting to think maybe plugged catalytic converters but I don't know of any way to test that. But it makes sense because of it popping/backfiring back through the intake. I don't know. I'm about to part out this car, I'm tired of it.

[Ebbtide]

You seem real close to getting this ironed out. Don't give up buddy!

However, if you are going to part it out anyway, take a sawzall to the cats and see if you are correct. But if you are getting codes, its probably those.

I've heard stories about cleaning out the cats, but would not kow if that is even true. Good luck!

[GerryO]

Three dry and possibly clogged or injectors at the same time could be a sign of fuel contamination/fuel pump/clogged fuel filter low system pressure problem.

Ideally a fuel filter should trap particles before they can clog an injector and even one bad injector will cause the engine to run very roughly.

The three replaced bad/dry injectors ohmed out OK too?

How about using a Noid lamp to check the six injector harness connections for power to the individual injectors?

Contamination particles or water in the gas, meaning that more/different injectors might be clogged?

It's all pretty much about air, fuel, spark and the proper timing of it all, and the engine won't run for long if there is no air going through the MAF. Make sure that all of the intake ducting and sensors, and vacuum lines are connected.