What is the problem with my motor?

[NeoDrifter]

My new KA24E motor is not running right, could it be the valves stuck? mafs malfunction? Coolant sensor gone bad? Symptoms: 4th cylinder sounds like its not igniting, when I rev hard I hear a loud popping sound, a lot of white smoke comes out the exhuast, it takes a lot of time for the rpm's to go up, and it sounds nasty like a lawn mower. I put in new spark plugs, new fuel injectors, new spark plug wires, new distributor rotar and new cap, I tested for spark and there is spark in every cylinder. It smells like it's running extremely rich. Would the P.R. solenoid valve or SCV Solenoid Valve being d/c have anything to do with it? I'm gonna clean out all the contacts in my car tomorrow and see if that helps. Also the downpipe is not fully hooked up to my exhuast manifold however I don't see how that can affect the idle, anyway please help me

[NISTECH]

if the down pipe is disconnected in front of the O2 it can draw air in and cause the O2 to tell the ecm the car is lean therefor the computer increases the injector pulse width adding aditional fuel. As severe as you situation sounds I think it is more what you said (coolant temp connection or MAF problem) There are many threads covering this in 240 technical and here in online mechanic. check them out and see what you come up with.

[NeoDrifter]

ok I got new gaskets for the downpipe, and bolted it all back up and its still doing it, I tried running a new gruond wire to the MAFS no change, replaced the coolant temp sensor and still nothing, it idles at 550 and backfires periodiaclly when I rev it. Any ideas?

[NeoDrifter]

I also jiggled the connector around for the MAFS and no change

[NISTECH]

check your timing and do a leak down check on your injectors see if one is leaking. when you replaced the coolant temp sensor did you make sure the connector was free from corrosion and tight fitting on the terminals?

[NeoDrifter]

Gonna check timing tomorrow, and I replaced the seals on the injectors after I found #3 leaking, I even changed out the fourth injector and its still running like crap. Gonna clean out the contact for the temp sensor also gonna do a ECU engine diagnostic and see if that'll help if not then I'm gnona start to think maybe its a mechanical problem with the head. It sounds like a timing problem because the valve is open and the spark plug is igniting when the valve is opening so that's causing that popping sound in my intake and also the backfire in my exhuast, what do you think?>

[NISTECH]

I made the assumption the backfire was from the exhuast not intake. You might want to check your cap and rotor. look at the cap closely for carbon tracking ,if its made in italy toss it and get a factory one. The italian ones are notoious for causeing missfires. If the cap inspection reveals nothing you may have a mechanical problem either dist. out of time or chain off a tooth(less likely) do a thourough timing check.

[NeoDrifter]

ok thanks, gonna do that today

[NeoDrifter]

ok the backfire is comign from both intake and exhaust to clear things up, I checked the cap out and its brand new from japan as are the wires, so I am gonna get the engine at TDC tmorrow as soon as I can get a big enough socket to fit the crank pulley, now NISTECH can you give me instructions on getting the distributor back on time? or a link that'll tell me. I take off the front cover, pulley and all that after I get it on TDC then what? take teh distributor off the chain, turn it so the rotar is facing toward the #1 spark plug position and put it back on the chain? Also I need to know what to replace when I'm doing this, like chain, chain tensioner? This motor was pulled from a 1990 240sx so I think it might have a metal tensioner in it already, thanks

[NISTECH]

you do not need to pull the front cover to inspect mechanical timing. bring the crank pulley mark to top dead center. remove your valve cover and distributor cap. Now look at your cam pulley mark is it dead on where it is suppose to be for top dead center? is your dist rotor pointing to #1? if your cam mark is not right at top dead look at your distributor. if its pointing at wire #4 it is 180 out so rotate the crank one complete revolution to top dead again and see if all the marks are on. If any one is off you need to correct it. post your findings.

[NeoDrifter]

if its valve taiming it shouldn't be too hard right? just take the sprocket off and move it so its correct?

[NISTECH]

if the piston contacted the valves it would bend them. your engine is an interferance engine meaning if it jumps time it can bend valves.

[NeoDrifter]

ah damn, would I be able to hear it though? Like a clack clack sound as the piston hits the valves?

[NISTECH]

yes typically it will make noise.

[NeoDrifter]

ok, its timing ignition I talked to a friend who rebuilt a ka and said he also had problems with the distributor so I'm gonna see soon since I just got a nwe job so I can afford tools

[NeoDrifter]

Ok, I got the engine at TDC, and I swapped out the distributor and rotar and checked the plug wires. I started the car, and nothing still ran the same. The timing is still good, and right now I am at a total loss. I'm gonna run a compression check onthe motor, thinking maybe Cylinder #4's valves onthe intake side might be stuck open and letting some of the air and fuel out which might explain the popping sound in teh intake, all vacuum lines are hooked up, gonna put a boost gauge on to see if I have good vacuum gonna do an ECU swap and a diagnostic to see if I can find the problem and if the ECU swpa helps, any ideas on what it could be to this point?