problem stalling at high speeds but fine at slow speeds

[nissanpunkrock]

so i have a 95 240sxi changed fuel filter, plugs, wires, rotor, cap, and air filtercleaned my maf with cnc maf cleaner, relocated my knock sensor

no check engin lights or anything

so when im driving down the interstate, have to be going over 60the car will accelerate fine but then it will randomly just buck and stalland no matter how much gas i give it it wont goi can let go of the gas and then give it gas and it will be finebut a few seconds later same thing will happen if im still goin over 60if i stay under 60 the car runs fine wont buck or stall, nothing

also sometimes i can smell gas, but just a little and only when i just parkedaround town car is perfectits just over 60 and its only when the car is hot

thinking maybe was maf but it idels finemaybe fuel pump but its fine under 60

someone help thanks
Modified by nissanpunkrock at 7:53 PM 3/2/2008

[Big.London]

Check your fuel injectors, look for strange spray patterns or gunky buildup. if there's too much buildup it could cause them to be unable to open and close at high rates. Is it just the speed or is it your rpms. Because the engine runnin 6000 rpms at 30mph and 6000rpms at 60mph should be exactly the same.

[nissanpunkrock]

its just over 60 mphand its only when the motor is hoti drove on interstate for like an hour befor it startedsputtering and acting up

so i pulled over and smoked a cig and by time i was done got back in car and it was fine for like 3 min's at above 60 but then started acting up again

if it was injectors would heat have anything to do with it?heard something about fuel vapor lock or somehtingbut i thought that was just machanical pumpsand 240 is electricso im at a total loss

[nissanpunkrock]

just found something about vacuume leaks?does that sound like it could be problem?with my hood up, if i get my gf to cut the motor offfor like 3 seconds after its off it sounds like an air hose loosing pressurecomin from between the motor and the intake manifoldso maybe i do have a vac leak

but like i said prob is only at high speeds and its only when motor is hot...

[cbt240sx]

Sup, man im starting to lean more towards the vaccum system being the culpit in this. Rogoman left some tips on the other thread. I found an 89 FSM that line maps out the vaccum system, now its just finding the time to get out there and trace all of those lines down for leaks.

[Big.London]

Well if it wasn't the fuel injectors locking up i was going to assume it was a vac leak. The only reason i can think of heat effecting the vac system is that something is expanding with heat and causing the leak.

The fact that you said you hear a "sucking" sound coming from between your intake mani and your head would make me think either your intake manifold gasket is shot or an emissions issue. Maybe your EGR system.

Are you getting a check engine light? And if so, what for.

[nissanpunkrock]

no cel's are being throwni got one for maf and knockbut i cleaned maf and relocated knock and they both cleared

so i drove back home on interstate, about 230 milesand this time it acted up like 4 times but then it never did againi could not get it to do the same thingthe problem just kinda lefti think it was a little cooler air temp wise on way homebut other than that nothing was differenti dunno what the prob itima take it to a shop get em to put a vac on intake see if its leakingbut hell ima just stay off interstate till i can get it fixed

[youngun21a]

I would still check the injector to make sure they are sitting right,Cause I had that problem had no power at higher speed but it slow speed it work fine,and If press on the gas it would hesitate like it was running on 3cyl so when back home and see #4 injector was showing a little silver around the intake,so I remove the fuel rain and reset the injectors and it has work good since.also check the hose under the throttle body.

[ghettoslide]

When was the last time you changed the fuel filter?? Higher rpm means more fuel needed it may be partly clogged.

[Big.London]

When was the last time you changed the fuel filter?? Higher rpm means more fuel needed it may be partly clogged.

It has nothing to do with his RPM's, because if it were RPM related it would affect him at any speed attainable in the problematic rpm range. (eg. 4000rpms-7500rpms at 30, 50, 70, 90, 110)

I think he's probably right thinking it's a vac leak since he does hear air being pulled into his intake after he cuts the engine.