idling problems

[s13180sx240sx]

ok this is what i have 1989 240sx hatch with a ka24e sohc

ok i rebuilt a sohc motor its in time . i removed the egr valve and the black box over on fender. i removed a/c and cruise control out of engine bay. i put motor back in and hooked everything up i labeled when i took it out.my question is my number 4 cylinder when its plugged up the motor will miss like crazy i unplugg it and it calms down so i checked my plugs #1 was clean #2 #3 #4 was black (maybe from when i had oil in cylinder walls when i was rebuilding. its also idling high around 2000 rpm and it calms down to 1200 when it gets warmed up its getting fire at all ends of plug wires havent checked the plugs yet to see if they r getting fire any help would be appreciated

[S13 240SX]

my sohc does that too.. i start it idles at 2 grand warms up and idles at 1,200 for the rest of the day and night when i drive it but i have no other problems with my spark plugs being black or miss-firing like crazy.. Black is carbon so run some cleaner in the fuel tank, thats may all it needs to stop miss-firing like crazy.. if it doesn't stop miss-firing re-check your timing.

I suggest using Sea-foam in your fuel tank don't bother using it in ur oil or break booster line. just the fuel tank. It works great!

keep me posted i will try to help you out the best i can, iused to have a lot of gay sohc problems when i swapped a better one into my 240.

[supra brit]

Haha just the opposite of my sohc. I have to hold the gas to keep the revs up when I first start or it will die, then after a few seconds it idles around 750-900rpms.

If yours plugs are black, definitely change them. Make sure you get NGK and make sure they are gapped correctly.

Also check your IAC valve and for vacuum leaks (KA's are vacuum happy motors). You might be able to adjust your idle down with the idle air screw on the throttle body.

[s13180sx240sx]

well when i rebuilt the motor i bought new ngk plugs and wires rotor button cap i bought all new stuff and i used the old throttle body and it idled just fine with other motor with the idle screw and as far as the seafoam stuff i use it alot i have 3 cars to keep up about every 6 months i put a bottle in my tanks. today when i get off wurk im going to check all my grounds and the all vacum lines. but what gets me is that i can unplugg the #4 plug wire and it still misses just not rough the motor quits jerking around just misses thats what gets me and as far as swapping for a better ka thats what i did here the other one was wore plum out and i won bought a rebuid kit from one of my customers real cheap so i rebuilt a motor i had from another 240 so i know everything is good in this motor just cant figure out the miss firing on the number 4

[S13 240SX]

Haha just the opposite of my sohc. I have to hold the gas to keep the revs up when I first start or it will die, then after a few seconds it idles around 750-900rpms.

If yours plugs are black, definitely change them. Make sure you get NGK and make sure they are gapped correctly.

Also check your IAC valve and for vacuum leaks (KA's are vacuum happy motors). You might be able to adjust your idle down with the idle air screw on the throttle body.

hahahaha yeah mine does that too when i first start it also.. i have to rev for a little.

[supra brit]

Check your timing then.

[s13180sx240sx]

well i stopped by and got me some new plugs ngks and i installed them cured the real ruff idle that i was having but now another idle problem but normal with nissans the rough idle the occasional jump in rpms the normal nissan stuff that is hard to figure out on each car and she is running great now i just gotta put my cold air intake on and try and get a header for it ebay all the way lol thanks for all the help next time sumthun happens ill do a search and post if i cant find anything.

[supra brit]

It's a sohc. Most e's and de's too don't always idle perfect. Mine can idle at like 600 one minute and 950 the next.

[S13 240SX]

yeah it can just be normal i think mostly its due to the weather.. i know dont know... but today it was warming up here and then my idle was back to 900, before it started getting warm out, it idle at 1,200 for days. 240's are just werid.

[supra brit]

These words describe about 90% of a 240: Works when it wants to.

[s13180sx240sx]

yeah tell me about it the wurking when it wants too is excactly right its kinda cold here and it idles around 1300 the other day when it was warmer like 50 degrees it idled at 800-900 it jumps anybody figured out why they jump like that