240SX (single cam KA) misfiring on cylinders 1 and 4

[coupeyy]

Hey everyone. I'm new to these forums. I got my S-chassis about three months ago. I've never gotten the chance to drive it, and I just now registered it. This is going to be my daily driver. When I bought it, the guy didn't know anything about 240's. (I'm not implying I know everything about them, just saying) I traded my car for his, and all he told me was that had a bad idle and needed a "tune up". I just recently got the funds to start working on my car and have replaced a bit of things for it. My brother is pretty mechanically inclined so I followed what he told me to do. I replaced the 02 sensor, distributor, cleaned the ISC, fuel injectors and mass air flow sensor. There was not any change when I did that. My brother and I were at the car one day and I told him to unplug injectors one by one to see if any were bad. So we did, and injectors one and four made no difference when they were unplugged. We cleaned the injectors, and checked the wires for current. After the injectors were cleaned we moved them to cylinders two and three just to see if it were the injectors themselves that were bad. After doing that, there was still no change. The idle seems to drop and eventually the car dies when I put the car in reverse/drive. At this point I'm really lost. :confused: That's why I've come to this website, because I'm sure there are people that are more experienced with the KA, as I've been working on the 4G63 more. (with my brother) I will provide a YouTube link as well so you can see the problem first hand. (Please take note that the rattling noise is not a rod knock, it is the exhaust hitting the driveshaft.) Thank you for any help, as it will be very appreciated. If you have any questions or concerns I will gladly respond to them as soon as I can. Thank you!




YouTube link for the problem: https://youtu.be/kwb1TtID7fg

[robinsone]

Ohm the injectors, they could all be bad. There are online factory service manuals you can get to properly diagnose the problem, those will help. Your idle air control valve iacv could be bad as well that happened to me. You can use the DOHC iacv on the SOHC I did and worked fine. Check your timing, vacuum leaks, the rubber intake hose just before the throttle body are notorious for dry rot, that happened to me. Too many things to mention, make sure your grounding is sufficient too. Here's a link.

http://www.nicoclub.com/FSM/240sx/1989/1989.pdf

[KendallH]

I assume you've changed the spark plugs? Measure continuity in the wiring harness between the injector connectors and the ECM. If you have a noid light, check to see if you're getting pulse signal to the injectors. If both are good check compression and leakdown.

[Reece]

Change the plugs and wires pimp

[coupeyy]

I actually got a noid light yesterday to check for a pulse and when I did, the car died. Could there be a short somewhere?

[coupeyy]

Plugs and wires are fine.

[coupeyy]

When I checked the injector wires for pulse, there was none. It was just staying on the whole time.