1990 240SX Gas smell, rough idle, misfire, overheating. Need help!

[damonfong0]

So I have all 4 of these problems, I'm not sure if it is just one thing causing it or a couple of things.

I tried searching and read through everything but none of them seemed similar enough.

Gas smell - Outside, it is very strong. Especially if driving behind my 240. Inside, however, there is no smell until usually after a while. Smells a little from the front but A LOT from the back.

Rough idle - This happens at random, for some reason sometimes my RPM drops very low and shoots up to 2k then drops really low again. Turning on AC was a temporary fix. A lot of smoke comes out of tail pipe and it shakes a bit when this happens.

Misfire - Rare but happens, the engine doesn't fire correctly and sounds like a subaru when i start it. (chok chok chok chok chok chok, instead of vrooooooooooooooooooooooooo) When I pop the hood the whole engine is shaking. This seems to be related to the idle though.

Overheating - For some reason when I drive fast this doesnt happen at all, when I am stuck in traffic the temperature gauge heats up. I let it cool down for 20 minutes or start driving fast again and the engine cools down.

So can anyone help me out and tell me what else I should be checking and what might be wrong?

What I did already:- Change oil - it was really black- Change Valve cover gasket + degreased engine a little- Checked fuel injectors - not leaking- Checked spark wires for wetness - dry- Checked Coolant - Full and green (edit 12/11)- Air intake piping cracked near intake manifold (edit 12/11)

To Do list:- Replace plastic air intake piping (edit 12/11)- Bleed cooling system (edit 12/10)- Check individual spark plugs (edit 12/10)

Just bought the car recently and the previous owner showed me smog papers. Started acting up 3 days later. If it runs, it runs good. If it acts up it's unbearable.

Modified by damonfong0 at 10:38 PM 12/10/2007
Modified by damonfong0 at 10:09 AM 12/11/2007

[n1smodr1ft]

i would try bleeding the cooling system for air bubbles. my car did the same thing after i replaced a thermostat and that was the issue. im pretty sure where the upper radatior hose attaches to the engine there is a bleeder. as for the miss fire check each individual cylinder for spark. just simply pull up each spark plug wire while the car is running, and which ever one you pull up and the idle doesnt change is the bad one. then examine your plugs and plug wires... also check your distibutor cap and rotor.

[navysnail]

there is a bleeder on the uper rad hose were it connects. rather than bleeding, i would recomend you change the coolant for good measure, this would be the time to do it since you are allready going to bleed it

as far as the idle and gas smell, check your IACV and MAF respectively

[Valett85]

ok, i have a 95 and i have the same gas smell. except it only smells when i park it in the garage. im guessing its a rotted line somewhere. it is coming from around the fuel tank area. Mine also idles hard sometimes at random. like. ill start it up 50 times just fine but them once in a great while i start it up and it idles hard a ****. im going to put a new distributer cap and blah on it. to see if it fixes the rough idle problem. as far as the fuel smell. i dont know. i dont know exactly where its commin from so im kinda lost.

[Valett85]

also...if bleeding dosnt help your cooling problem. you may need to replace your water pump (but its prolly air pockets). the reason it is cooling while you are driving is that air is moving past the motor. when your in traffic you are sitting still. please tell me you have... but have you even checked to make sure you have coolent in your engine?

[1990240lamb]

i have a 1990 240sx with the ka24de motor i eliminated the thermostate and replaced the water pump but it still over heats but no level change in the oil and no smoke out the exhaust dose misfire at idle but not when running what what could it be

[nifares240]

that overheating issues sounds like a bad clutch fan.

rough idle- check for any vacuum leaks as this causes erratic idle.

set the timing.