1992 240sx : putt-putting / cylinder maybe not firing

[astluis]

my friend is running the stock KA24DE with upwards of 250k miles.

once we got it back to town after buying the car began to putt like a lawnmower. there was no noticeable loss of power. no smoke. timing very slightly off. engine rocks back and forth quite a bit at idle.

my first suspicion was a vacuum leak, but we found no damaged/loose tubing.

shortly thereafter there was a very noticeable loss of power. no change in the sound.

next we checked the plug wires. one of them was a little screwed up so we replaced the wires. problem persisted.

we checked the spark plugs for unusual residue/cracks/etc and found nothing out of the ordinary.

we checked compressions and they all checked out.

we removed the plugs from the rotor one at a time and found that there was no change in behavior when #3 was removed and replaced.

not knowing if we're just imagining things with the cylinder or if it in fact isn't even firing we decided to do another check for vacuum leaks to be safe. this time we found one of the tubes committed seppuku. this confirms my suspicion of a leak for the funky idling but there's still the matter of the loss of power and strange behavior of #3.

there's no smoke, no loss of compression, wires changed, plugs checked out, cap and rotor look alright

are we missing something critical here? should we take a closer look at the cap and rotor?

thanks in advance.

[NISTECH]

pull the plug in number 3 and see what it looks like, black,white,wet, or clean?

[astluis]

the plugs looked fine. either clean or with a miniscule bit of white powder. he switched out the plugs and the problem persists.

[NISTECH]

You need to see if its firing that injector or if the injector is electrically ok. to do this first go get a noid light from autozone that will plug into the nissan injector connectors. 1 of the GM ones will work , the other one they sell obviously wont so you should be able to find the correct one. Plug it into that connector and see if it flashes with the car running. If it does you need to see if the injector has the proper resistance. Use an ohm meter to check resistance across the terminals in the injector with it unplugged. Then measure the one next to it , should be with in 2 or 3 ohms of each other [usually almost exact] If this checks out it may be mechanically stuck closed. If this is the case , with it all put together and the car running, tap it a few time with a hammer on its metal hat. If it is stuck this MAY unstick it.

[astluis]

the injector is getting the proper signals, so we tapped the hat to see if it would get unstuck. nothing changed and so we're gonna switch injectors to see if the injector is gunked or just plain screwed up mechanically.

[NISTECH]

NOO you will distroy the injector pulling it out. How did the ohms look when you tested them?

[Young_240_Guht]

NOO you will distroy the injector pulling it out. How did the ohms look when you tested them?

wish i would of found this thread b4 i tried... and autozoner Discount days is over and i cant get a cap from there, i cracked it aswell... this is my first post

A. G.