rough idle problems

[leemellor]

k here is my problem. I have a 91' 240sx fastback. I have a rough idle problem. It will start up fine but once it warms up the rpms range from 1100 rpm to < 100 rpm sometimes even to the point of stalling. I can bring it back up to a steady point by giving it a bit a gas and eventually it evens out. At this point if i give it even the slightest bit of gas the rpms will act up again. I had a tuned muffler on there and i thought that might be the problem so just today i put a stock one on. Didnt' help. Had a tech do a diagnostic on it and he could basically only tell me that it is running rich and he suggested i clean the throttle body and check the plugs. so i did. Nothing still. I then thought the cat converter was plugged....nope, it's all good. here is a recap of things done-sprayed intake with throttle body cleaner-checked plugs-replaced muffler-checked cat converter (there is still a rotton egg smell sometimes too)-replaced O2 sensor

I'm out of ideas......it seems alot of people have this problem but no one seems to know why....or when they find out they never come back on these things and tell anyone what they did.

So if anyone has any suggestions or ideas i'd love to hear them

Thanks alotLee-

[hapaboi39]

I have a 93 coupe with a Ka24de stock motor which did the same thing. I replaced the fuel pressure regulator, the fuel filter, cleaned the AIV but still to no avail. After i threw a bunch of money into it blind I broke down and had an ASE guy diagnose it. The main culprit was the Mass Air Flow Sensor. I picked one up used at a NIssan dismantler for 125 bucks and had it installed for like another 50 bucks. The problem went away for the most part but i still had like a little roughness idling. I went ahead and ordered the NGK blue plug wires from Japan and now my car runs like a top!!!

So check out your MAF and go from there.

Good LUCK!

sami!

[sleepyRPS13]

hmmm you must be running rich at idle. maybe try the propane enrichment at idle. if rpm drops or stalls its rich or if it picks up it needs more gas.

check the iac & vacuum too while your at it.

[leemellor]

that's sweet manthanks alot for the tip.If anyone else has any good tips they are welcomed

thanks again

[sleepyRPS13]

you can also find vacuum leaks with propane.

[leemellor]

thanks for the tip mani checked it but nothing seemed to have come from it. NO vacuum leaks!!!!!! which is good to know atleast one thing is ruled out

thanks though

[hapaboi39]

Check your maf dude, i had the same problem almost to tha "T" that your describing. Slapped on a used one and now its all peachy.

[onpoint357]

Im having similar problems, I was told the following: Mafs, thottle position sensor could both cause this also check crank position sensor.