please help me out with my idle problem!

[jiffy08]

Okay, so here's the deal. The car is a 92 240sx with a totally stock ka24de with the exception of a 300zx fuel filter and hks exhaust. My car's been running fine for the two years that I've owned it, no problems at all. Just a few hours ago I was sitting at a red light and I stalled when it turned green. I normally don't do this, I just figured that I happened to fail at driving a stick. However, I started to observe it a little and when I came to another light, my idle seemed to jump between 600-700 rpm, which isn't too bad, but then it would randomly go down to 200 rpm and shoot back up to 900 and back to normal. I had to keep my a/c on to keep the rpm's relatively high. If not, I would hold the gas pedal a little just to keep it from stalling. When I got home, I sat and observed the rpm's and it did the same thing, almost stalling twice until I just shut it off. Also, I am not sure if this matters or if this tells you guys something, but my CEL turned on twice when my rpm's got too low, but it would go away within seconds. What could my problem be?

Sorry for the long read, I hope you guys can help me! Sorry if I'm asking noobish things

[driven_]

hmm.

sorry to threadjack but my s14 does something similar.

it'll drop as i enter 1st, from neutral and then as i gas it would be normal.

hope you find out.

let us know.

[hilux30]

well, there could be few things here to explore and these are all possible, some require special tools: check fuel regulator for loss of vacuum pressure, check timing, distributor to see if cam seal is leaking oil in the cap and rotor area, coil going bad? All in all, I might be wrong but it seems like the fuel pressure regulator is starting to go. checking it requires a vacuum tester, pull the vacuum (small) line going to it and use the tester to pump pressure, if it drops quickly then here u go....

[dllkbales1]

You said your cel came on, CHECK ENGINE LITE ? If so then there should be a code stored. Pre 96 vehicles are a little tought to pull the codes so you may need to pay someone to check for them. Follow the codes, If the system is seeing a problem, its trying to tell you about it. Also check to make sure that the vacuum hose to the fuel pressure regulator is not sucking fuel into it. If so the regulator has a small hole in the diaphram and unregulated fuel is being drawn into your intake thru the hose. Your car wont know where the fuel is coming from and the code will be for a rich condition.