Running on 3 cyls

[DjLiquid]

OK. Here we go again. I got the car in the garage and started tinkering with it. I swapped the ignition module and it still did the same thing. I undid each coilpack 1 by 1 from the harness and tried starting it to see if this would number it down to what coil pack was dead. When I got to cylinder #4 and had the harness unplugged, it was as it nothing changed (ran on 3 cylinders) so I knew it was this coil pack.. I swapped it out with a good one and still the same thing happened.

I then figured it might be a bad plug so I unscrewed it and for the car only having about 50km's on it, the spark plug was loaded with carbon. I sanded it off and made sure it was sparking by unplugging the coil pack but still grounding it and had the spark plug in the air while cranking the engine over. I could see the spark. Now after being totally dumbfounded I decided to check over the wiring. I checked the injectors and it seemed like injector #4 was loose so I pushed it in better and started the car.

VOILA!!! it ran smoothly. I set the idle lower and took it out for a drive.. After I went around the block it started raining. Since I have a hood scoop on my car I decided to head home. At a stop sign, I gave the car a bit of gas and went up to about 60kmh pretty quickly.. 1- 2 - 3, then let off the gas. Once I let off the gas and downshifted into 2nd and gave her gas she started running on 3 cylinders again... BAH!!!... I brought the car into the garage again and checked the injector connections and it was good. I hooked up an ohm meter and the connection is working. Now I've either narrowed it down to a crappy fuel injector or a bad spark plug.

Im going to go out now to get some new iridium plugs but I was wondering if there is anything else I should pickup while im out. I figured maybe some fuel injector cleaner or something like that.

Also, is there any way to tell if the cylinder is actually getting fuel into it?

Thanks!

[NismoBgt]

Well... One way to tell is a temp probe testing of the exhaust. Truly only works on cars with tubular exhaust but it it does work to a small extent on cast you just have to measure right at the head/manifold. I have a Fluke Volt Meter that has a temp probe as part of it. When I was running multiple carbs I used it as a tool to help tune each carb. You could measure which cylinder was running richer or leaner by the exhaust temp.

[DjLiquid]

Hmmmm. Well, I cleaned off that spark plug again and swapped the coil pack back to my old one and it's running on 4 cylinders again... Now can someone tell my why im running so rich??? Ive done absolutly nothing to this engine with the exception to some slight head work, 300zx maf, and thats about it.. Is there any way to tell if my O2 sensor is working? Im all out of idea's

[biosehnsucht]

with the 300ZX MAF, what is controlling fuel?