missing on #3 1992 240sx ka24de

[peashooter]

I have a miss on #3 cylinder. I have replaced the injector, tested the spark. All ok . Do not get a pulsing signal on the connecter. I get a constant 14. +-dcv.Any other tests?

[nisssan-drive]

how did you test the spark?

[peashooter]

took the plug out and laid it on the engine while my help cranked it(the engine).Spark looks good. There are some things I forgot to mention. The car did this intermitantly. It started by missing one day and I removed the #3 wire and plugged it back in and it ran fine for a day or two. It started missing again and I removed and replaced the plug wire at both ends. It did not fix the problem. I changed the wire from #2 cylinder with the #3 wire to see if it would follow the switch.It did not. I disconnected and reconnected the #3 injector wire. It ran fine for a few more days. It started missing again . I did the wire wiggle again. It did not help the 2nd time. I replaced the injector.It still misses and that is where I am at this point. Thanks for the reply

[leper421]

If you have a timing light that hooks onto a spark plug wire to fire (every timing light that I know of), hook it up to the plug wire for cylinder 3, and shine it on the crank pulley. You may need to paint a mark on the pulley at the point where the cylinder fires. If the point doesn't jump around when viewed with the timing light, then it is not missing because of the spark. The point will move when you open the throttle, however it should be steady as long as the RPMs are steady.

[peashooter]

Spark is ok using timing light.

[Vegascorbin]

if you have a friend with a working ECU try a swap. I had a similar problem with my #4 and it ended up being the ECU itself.

[peashooter]

Don't have a friend with a 240sx. Is there another way to test this thing . I 'm fairly good at testing some electronic systems with a multimeter.The number on the ECU is A11 B44 G70

[leper421]

I have a miss on #3 cylinder. I have replaced the injector, tested the spark. All ok . Do not get a pulsing signal on the connecter. I get a constant 14. +-dcv.Any other tests?

I assume you are talking about the voltage to the fuel injector connector.... How are you measuring this voltage? Without an oscilloscope, you will most likely see the voltage as constant. Your average voltmeter won't measure voltage changes at the frequency that the fuel injectors fire. Although since the injector should only be on for a fraction of that time, the average voltage shouldn't be anywhere near 14v. 14v continuous should either fry the coil in the injector, or at the least continuously dump fuel into the cylinder.

I have a spare ECU for sale (large number is "24", small number "A11-B44-G07"). Its from a 91 manual. Its listed here: zerothread/336274

[peashooter]

I have a miss on #3 cylinder. I have replaced the injector, tested the spark. All ok . Do not get a pulsing signal on the connecter. I get a constant 14. +-dcv.Any other tests?

something I noticed when checking the timing again. The timing mark for #3 cylinder travels completely around clockwize as the engine turns .I've never seen any car do that and the thing run, even badly.

[peashooter]

HELP

[leper421]

something I noticed when checking the timing again. The timing mark for #3 cylinder travels completely around clockwize as the engine turns .I've never seen any car do that and the thing run, even badly.

I forgot to mention that to time the 240 you have to disconnect the TPS connector. Its one of the large connectors at the front of the intake manifold, above the radiator hose. There are two large connector there, it is the one with three wires, not four wires. Warm up the engine, then shut it off, disconnect the TPS, then start the engine again.

Does the mark still jump around? Try hooking the light up to the plug wire for cylinder #1. Does it still jump around?

Also, with the engine warmed up (TPS connected) disconnect the fuel injector connectors one at a time (reconnect before disconnecting the next one). Does one cylinder cause more or no change in the idle?

[WWJD]

HELP

in my case I've gotta leaky head in cyl. #3 which causes back fire run a leak down or check CP test

[peashooter]

To recap; I have a miss on #3 cylinder.It originally whould stop missing for a while when I wiggeled the injector wire.It started missing all the time after a few days. I have swaped #2 sparkplug wire with #3 sparkplug wire. It still misses on #3. Wire is OK. There is no backfire. I swapped #3 injector. After changing injectors, It run smooth for a few seconds Then back to missing again. I am currently replacing the fuel pressure reg. The only thing I cannot check is the ECU. Is there a way I can check the ECU other than swapping it for an other. I hate to spend the money on a bad diagnosis on my part. Thanks for all your help

[leper421]

To recap; I have a miss on #3 cylinder.It originally whould stop missing for a while when I wiggeled the injector wire.It started missing all the time after a few days. I have swaped #2 sparkplug wire with #3 sparkplug wire. It still misses on #3. Wire is OK. There is no backfire. I swapped #3 injector. After changing injectors, It run smooth for a few seconds Then back to missing again. I am currently replacing the fuel pressure reg. The only thing I cannot check is the ECU. Is there a way I can check the ECU other than swapping it for an other. I hate to spend the money on a bad diagnosis on my part. Thanks for all your help

How do you know it's a problem with cylinder 3? Please describe how you determined which cylinder was misfiring. Are there any ECU error codes?

[peashooter]

I removed the plug wires one at time to see if there was any change in the way it ran. The only time it did not change was on #3 wire. There are no ECU codes

[leper421]

I removed the plug wires one at time to see if there was any change in the way it ran. The only time it did not change was on #3 wire. There are no ECU codes

With the engine off, disconnect all four fuel injector harness plugs. Measure the resistance (in Ohms) across the two pins on each injector. What are the values?