Another KA stuttering

[89dc240]

I have searched but all the threads I found end with no answer, or end with a simple fix for which I've already tested.

93 ka24de, cyl number 4 not firing off. Ive gone through a bit of troubleshooting, and I'm looking for any ideas on what could be wrong.

What I've done:(in no particular order)
Check plugs and wires(spark present), check connector to injector(pulse present), checked resistance on injectors(all 11.5ohms or so), checked compression(way better than I expected), changed out #4 injector with 3 spares to no avail, changed one of the spares to cylinder 3, and good one from 3 to 4, and success. Well almost, I didn't have the injector fully seated and I believe fuel was getting past the o-ring.

At that point the car was running smoothly again, except when I would come to a stop, I could hear the fuel pump working harder(sounded like that), and there was some surging goin on, I believe due to no pressure being able to be built up at that #4 injector. I got it back home, switched out the injector again, and I'm back to stuttering.

I have also sprayed some carb and choke around the manifold and vacuum lines to check for air leaks.

This all just started Friday after I got done work, fired up the car and knew something was wrong. It ran fine on the way to work though.

I'm gonna skip the leak down test because the engine ran smoothly when the fuel was going around the injector.

Any input will be appreciated.
Hopefully I am just missing something simple. :bash:

[4x4le]

it could be the cas in the distributer or the wiring related, however what would go against that would be that your getting pulsing at the clip that would indicate that all of that stuff is indeed working.

[nismo240sxdrifter]

When you replaced the injector did you replace the o-rings?

[89dc240]

I wish I could say I replaced the o-rings, lol. I wanted to. I'm pretty sure they are ok. I replaced the fuel pressure regulator with a spare I had, based on being able to blow through the old one with no vacuum, and not being able to blow through the spare one. I also tested to make sure the injectors were working, by hooking three AA batteries end to end with a wire coming from each end(pos. and neg.), then tripping the injector manually. All the spares did not function. the original was good.

Anyhow, it seemed to be working fine after I replaced the fuel pressure regulator, drove it to work Monday, get back in after work and now the car is actually backfiring. I think I have an exhaust leak at the front of the cat,(similar symptoms to when I did before) from a quick fix weld job I did there like 6 months ago. And so I think the EGR might be affected by that. And maybe I'm just not getting enough fuel because there is too much exhaust, being pushed through the possibly, constantly open EGR Valve. Which has probably 242k on it.

I'm gonna take care of the exhaust leak, and then we'll see about "permanently fixing" the EGR.

*EDIT* I might be jumping the gun on the leak, and hoping that fixes the problem. The plug was black in #4 after I got home from work monday(all 4 were fine until then, the others are still good). I changed it out and the car was still running on only 3 cylinders. Now that I think about it, I could have damaged the o-ring(s) on the #4 injector. But I only drove about a mile or so and at low speed, so the plug still looks new/slightly brown. (I Know on a two stroke you check the plug after like a 1/4 mile pull when you're jetting it, so I figure the mile was enough to get a decent read on that plug) But I can't say. I still have some work to do.