engine runs crazeey yo. Help!

[miUnikTwo40]

check it out. the engine will crank and run, but it wont idle. if i take the fuel pump fuse out it idles great as if it was getting too much gas which i think it is i can smell it running very rich. if i smash on the gas and just rev it does this just fine but when i try to cruise with the rpms at about 3-4grand the engine goes into surges and i just have to drive fast. has anyone ever had this problem b4? anyone can answer this or jus give me somekind of info on this matter will be greatly appreciated. thnx!

[USDM240]

do you have higher flowing injectors? it could be forcing to much gas into the compression chamber. if not, your pump may be overpumping.

[frapjap]

May be a vaccum leak somewhere, take a good look around.

[KAcoupe]

check the the big line on your intake closest to the intake manifold....a lil more specific...couse with out that you def wont be able to idle maybe that is the prob idk just me two cents

[miUnikTwo40]

thankz guyz 4 all of your help i will definitly look listen and try all of your suggestions. im new to this site and i jus wanna say thanks to all that has attempted to help me in solving this problem. i will do my part in this club. u can count on it. i've had mi 240 for 6yrs now, and ive just about did everthing to it so far as repairs go. i jus never had this problem before, but yeah thanx

[frapjap]

To be a little more specific, get some carb cleaner and spray around the vaccum lines until it revs. When it revs you've secluded your problem/line/area. Then you can look more thoroughly.

[ka24depower]

hey man i have a 90 240sx and mine was doing that and i couldnt figure it out for a while but it ended up being the throttle air bypass valve.

[Dattebayo]

You mean the IACV.

Its on the back side of the plenum up against the firewall. You know, the thing with the idle screw attaches to it?

Surging can also be a injector problem, maybe a injector stuck open or a o-ring thats busted in the fuel rail. If so you should be able to detect a mild to strong odor of gasoline under the hood when idling.

I have never ever heard of your pump "overpumping". Sounds kind of ludicrous to me.