1993 240SX running on 3 cylinders....HELP!!!

[sethulrich]

Ok, I need some serious help.

First off, plugs, wires, rotor, and cap have all been replaced in the last couple of months.

Car was running fine. One day it starts running on 3 cylinders. Before I get home, it smooths out, running on 4 again. Check ECU codes, only one is knock sensor, which has been on there for like, 3 years, and not caused any problems thus far.

A couple days later, it is running on 3 again. Check the codes, get code 21. I replaced the coil and the little chip module that is right beside it. That cleared the code 21, but it still ran on 3 cylinders. A couple blocks later, it smoothed out again, running on all 4.

Two days later, running on three again. Only code 34 is showing up. Check the spark plugs, they all look normal. By pulling the plug wires one at a time and starting the car, I determine that it is cyl #1 that is out.

Since the plugs all looked normal, I guessed that cyl#1 injector was not injecting any fuel. Today I replaced the #1 injector with an extra one that I pulled from my 91 240SX. (KA-T in progress, replacing the stock injectors with 550cc...nothing wrong with the original injectors).

That's when things really screwed up. It now idles WAY worse than it did before, it is runnning pig freaking rich, and smoking like crazy. Well, I limped it home, which took more than half a tank of gas for...maybe ten miles. That was the last thing I expected would happen by changing an injector!!! I checked the ECU codes, only code 34. Checked the plugs. #1 is still clean, but soaked with gas, and the rest are all fouled black. I can smell gas, but there is none leaking around the injector that I replaced, or anywhere else that I can tell.

I'm at my wits end with this, especially since my 91 240 is in pieces because of the KA-T project....a fine time for my second car to screw up.

So I can determine the following:

#1 cylinder is not firing. I don't know if this is because there is way too much fuel for it to be able to spark, or if it is something with the ignition system itself....most of which has been replaced this year.

#2, #3, and #4 are firing, but running extremely rich.

Could a bad knock sensor cause this to happen all by itself??? I have the sensor, and will be replacing it soon, but it really doesn't seem like all this could be caused by a bad knock sensor!

And I don't understand at the onset of the problem, why it ran on 3 cylinders, then 4 again, then 3, then 4....

HELPPPP!!!!!

[180fan]

so let me get this straight, you popped in 550cc injectors, didn't get the ecu flashed, and now you're wondering why it's running rich?

[sethulrich]

Noooooo....I know you get a lot of newbs with dumb questions, but gosh I'm not that dumb!

The 550cc injectors are installed in my 91 240SX that I am in the process of building KA-T...I used one of the old stock injectors from the 91 to replace the #1 injector on my 93.

I thought I explained that clearly the first time....but it was kinda a long post so I'll forgive you for skimming over it and missing some of the details.

Anyway, I pulled out the #1 injector again, and the o-rings were both torn quite badly. My guess is that the o-rings were brittle, and when I installed the injector back into the rail, they got torn, instead of flexing like the rubber should have done.

New O-rings are on the way, I'm hoping that will take care of the problem.

[180fan]

right on. yeah slap on some vaseline on them o-rings when pushing in the new injectors. yeah didn't quite get it clear when you mentioned moving around injectors and this and that.