Rough idle/running rich

[240sxKAT89]

Hey guys, i know there is a bunch of post pertaining to these topics but i just cant seem to find anything that works for me.I have an 89 240 with a ka24de swap. First off it idles rough, at about the 1200RPM range when cold and between 500-1000RPM when warm. if i unplug my MAF sensor it goes to about 1000RPM and the roughness is virtually gone but plug it back in the problem persists(i changed MAF and it did the same).Also when i drive down the road it sputters and blows out smoke like there is too much fuel. When i try to start it it usually floods up right away and i have to unhook the injectors to clear it out. i check the spark plugs and they are wet. i vacuum tested it and it sits at about 15psi when at idle, i understand it should be at 18psi at idle. I most likely have a vacuum leak but will it cause problems at that extent? Do you think maybe a sensor is bad? Please help me out i have been trying everything and doesnt seem to work. If i left any valuable information out please let me know and i will post what you need to know.

[jml062088]

lol does the motor shake and flames shoot from the exhaust too? it really sounds like i am having the same problem as you are, and i had it diagnosed and it came up as maf sensor o2 sensor and the knock sensor. did you buy a new maf sensor or get a used one? i got one from the junk yard but im pretty sure it doesn't work everyone i ask says it might be that but im not trying to spend over 500 bills for a new one. if i figure it out ill let you know what the problem is. or if you do first please let me know what you found.. ill keep ya updated.

[jml062088]

ooh and another thing. when you give it gas without the maf does yours not rev past around 3-3500 rpms?

[240sxKAT89]

Yeah, when i have the maf unplugged it idles realy nice but i cant rev it up. so i was thinkin of running a switch inside the car to take power away from my maf while i idle and flip it back when i go.Haha i know its ghetto but its just temporary and a quick fix. and no i dont have flames yet, is your timing of maybe. it sounds like your exhaust cam is staying open too long, but idk i could be totaly wrong.

[Phantez]

I just did the same swap and had the exact same problems. I ended up having a bad wiring harness because one of the wires to the MAF was clipped, and the ECU was also bad. I would check those two things. Hope that helps

[nismopu]

Any change in fuel pressure make KA's not happy! They run rather large injectors IMO for the size/power output and the FPR is what helps set the amount of fuel they see. SO, if there is that much of a pressure difference than what factory specs call out I would start there. peace.

[youngun21a]

Mine dies when I uplug my maf for a couple of seconds.

[leveloneae86]

this thread is coming along good. already has a lot of useful info. bump for more, im battling the same issue.

[tbradley222]

this thread is coming along good. already has a lot of useful info. bump for more, im battling the same issue.

agreed and seconded lol

[wdyrland]

mine is also runnig extremly rich shooting flames and such. it is a 90 240sx with a ka24de swap. also mine does not seem to hold an idle very well. it is sputtery if i try and leave it at a stedy RPM it just shakes like crazy. i will get off the gas and most of the time it will just stall out. any ideas would be appricated i am ablout to give up on my car i ahve replaced o2 sensor, mAF, and the temp sensor.

[Wc240]

have you tried checking/adjusting the base timing? base idle mixture? checked your fuel pressure? dist. cap and rotor? plugs?checked for vacuum leaks?you got a long way to go before you "give up" start with the basics then get back with what you found

[T3AMV3XIZZY]

mines does the same .....everytime i am at a light i have to put it in neutral or else it chokes on me .....and shakes like hell wen i have it in D

[gardnerlawncare]

did you all ever figure out what is wrong, my chokes jout now and i have done a complete tune up and compression check, trying to figure out how to do a fuel pressure test

[Wc240]

id suggest doing a idle adjustment and checking your timing. sounds like when you go off throttle/idle, its flooding and putting out the spark

[ka24demiller]

I have been workin on the same problem, at least six months on this. I have pulled the motor apart three times just checkin for anything, This is my first inport build but not a newby the engine field. I have check and check this is gettin to. Anyone want to buy a ka24de rebult from top to bottom on new parts, arp fasteners, comtic head gasket, brand new head, pistons, rods, cranks and bored 20 over, will sell. I have a ls1 to go right in its place, if intrested let me know.

[lexcrob]

hmm.. vac. guages for carb. engines not really todays engines what ever works tho

-Well id say most of your guys problems sound like
1 vacuum leak(spray down with carb cleaner=smooths out idle.fuelinj.,vac lines,gaskets,brake booster,pcv
2 tap those sensors wiggle connectors
3 honestly its not always a sensor even with a code ....do the resistance checks they easy(they can be a tiny bit off)
4 PUT A GROUND FROM ENGINE TO CHASIS - to many times its a grounding problem
5 check battery connectors nice and tight u'd be suprised
6 check your oil level easy but doesnt help if over or under JIFFY LUBE dont alway double check
7 clean ur maf with electrical cleaner its UBBER important in airdensity system

If youve checked all or most of these things you have got yourself a problem! Back track do a compression test and or a leak down test if all comes out good then im sorry! Best way is to knock out all possibilites by convinence...borrow buddys ECU then go buy a MAF from adv. auto then clean and return when thats not it. ECT IAT sensors....blaa bllaaaa bllaa

Just start with the little stuff i always go to far and miss that ground or TINY pin hole leak in vac hose. TOO TOO many times

[lexcrob]

Ok i take that back about the vac gauge its a very useful tool just not normally in a auto techs tool box today. Its all scan tools and multimeters today im just saying that because i was working on my brothers FD and needed one and was pissed i didnt have one..........