1989 240sx: backfiring up the intake tried evrything

[dnlx5]

ok so i have a ka24e in my 240 and i was driving dove the freeway and as i accelerated i started hearing a pop pap backfiring sound. I pulled over and found that the sound was coming out of the intake.

I decided to limp it home and then guessing that it was a valve i pulled off the intake manifold ( found a rotten intake gasket next to the watter channel) ( #1 cylinder port was really dirty with like corbon deposits) and did a visual inspection of the intake valves then exhaust then i compression tested it then i put it all back together with new gaskets new cap new rotor new spark plug wires (probably should have changed the spark plugs but didnt wana foul up new plugs)( I also tried a new mass air flow sensor but this did nothing)

i did actually put the engine on tdc and found that the notch in the cam gear was straight as the 2nd notch in the flywheel was passing the timing point

still doing the same thing thanks in advance sticky valve? change the damn plugs?
Modified by dnlx5 at 7:33 PM 9/17/2007

[Twilight sentra tuner]

sounds like the timing might be off. check to see ur timing chain condition to see if it jumped or something.

[Florida240sx]

Change 02 sensor? Sure it's coming from the intake?

[dnlx5]

ya its coming from the intake funny story about the o2 sensor the plug fell of of my wiring harness so i put a new (universal) o2 sensor on and used a butt connector. the wire coming off of the wiring harness seems to be a wire within a wire with insulation around the inner wire. i connected my 1 wire sensor to the inner wire does this make any sense ill check the wiring

[Florida240sx]

Is the universal one a single wire? Just disconnect it and see if anything changes...You pulled the plugs yet?

[dnlx5]

yes it was a one wire universal o2 sensor ill try disconnecting it. as for the plugs i did look at them and they were prety sooty but none were showing any like spots or anything and none were broken. i figured id better fix the problem so as not to foul up new plugs.

[roosevelt]

when your lobe on your cam is wiped out you get the same results and the popping should synched (means constant popping when it pops) to the incomplete combustion of that cylinder.

if the timing is out you are likely to get the pre-ignition (ping)or difficulty in starting but may also POP or puff back into the intake.

[dnlx5]

i gueass i forgot to mention my walve click i have had it forever so i thought it was a non issue..... i tried some more stuff but still couldnt figure it out. i finally gave it to the mechanin and he heard the valve click. he replaced the 1st 2 rocer arms and its fixed. i kinda knew the lifters in the rocer arms were colapsing but apparently the hydrolic piston on the cylinder #1 exhaust rocer arm lifter had completly fallen out and thus the exhaust valve was not opeaning and the air was being forced back up through the intake. thank you guys all for givin me your knowledge i guess sometimes it takes an experienced tech actually seeing the problem firsthand