ka24de missfire and rpms dropping

[geborski]

ok need some help and info my 93' 240sx coupe with ka24de has a missfire and my rpms have been dropping when it goes into neutral. ive had the rpm dropping problem before, i changed out iacv then it went away for about a month and came back. swapped out my knock sensor and then the problem was gone for a week. checked my grounding and it was at 30 ohms, made a grounding kit for it and it went away for month and a half. now it came back two weeks ago and the rpms drop and stay down until i stop or it stalls out. ive changed out a bad injector on #4 cylinder and swapped plugs, plug wires, rotor and cap. rpms still drop but not as frequent and not as bad but regardless it still drops pass 500 rpm, and the missfire is still there

[NISSAN240SX12]

have you replaced your TPS Sensor yet?

[blackandblue]

you didn't say, but I assume you have a manual transmission. I notice with my manual I get an RPM drop when I go to neutral and let out the clutch. It doesn't drop below 750 because I bumped up my idle after i removed the mechanical fan. What have you done to the car as far as mods? If there aren't any major mods or recent rework, I would say check your ignition timing and set idle by the book. If your timing is way off the ECM will ry to compensate, but it can only do so much. Factory Service Manuals are out there, just search. Make sure they are all good before you go replacing more parts.

[geborski]

the car is bone stock except for coilovers and auto to 5-speed conversion, no engine mods yet. the tps is still good as far as i know. my timing is good but it has been advanced a little to help keep it from stalling out when i hit stop lights and my idle is good at 700 rpms. i had a buddys mechanic friend look at it and he said i had a really weak spark on #4 and #1 cylinder, ive changed plugs, wires, cap, and rotor as i mentioned earlier but no change, so im wondering if my distributor is bad. anyone know how to check if a distributor is bad other than buying a new one?

[sx moneypit]

If the distributor is bad it will affect all the cylinders.

[Klits562]

my idle would drop when i came to a stop, sometimes it would be really bad and my car would stall and sometimes the idle would just bob up and down but my problem was from vac leak. If your idle problem sounds like mine then look around for any vac leaks.

[geborski]

i adjusted my distributor and it helped with the missfire but it still has a slight miss every once in awhile, i drove it around the block a few times and the rpm drop is still there. i tried pulling the codes again off the ecu and it finally threw a code 43 so im going to replace the tps and see if it fixes everything.

[geborski]

uggggghhhh!!.......well i swapped my tps out but my rpms are still dropping, the only thing i can think of next is a vaccum leak. does anybody know of the most common places to have a leak so i can start there?

[sx moneypit]

You need to check your intake gasket for a leak. I have replaced quite a few over the years.The stock gasket is made with some pretty thin material and will get sucked down into the intake ports.It will cause the symptoms you are having.

[geborski]

well ive been driving it around for a couple days now and think the problems solved...for now. i swapped in a different ecu and all my problems have seemed to have vanished. i guess the ecu i had was s***. wish i knew that before i bought all those other parts. oh well.

[sx moneypit]

Hope that takes care of your problem and it doesn't bite you in the a**!Keep us posted!