Bucking / Hesitation when hot...

[Hubie]

I get this horrible hesitation/bucking when I drive my 96 240sx for about an hour in these 95+ deg. temps here in Texas. If I ease on the throttle it'll be ok but as soon as I try to take it up a little fast it will start to buck. I don't know if it was just a coincidence but when I have a full tank of gas it doesn't do it as bad as say 1/4 tank.

BTW I already put on new plugs, wires, dist. cap and rotor, fuel filter when I got the car 9mo ago. Original O2 sensor but would it cause this...?

Oh yeah, I took my MAF sensor off to clean it with electrical parts cleaner about a month ago and this didn't start hapening until about 2 weeks ago. So I don't think I damaged it. I think I'm go around to all the connector and shoot a little contact cleaner into all of them.

Thanks for any help.

[NISTECH]

sounds like ignition drop. check your wires real good for arching under load. also if your cap and rotor says made in italy i would recommend you replace it with factory or at least one made in usa or japan

[Hubie]

All parts used are OEM Nissan.

Could it be the fuel pump? Is there any way of checking it other than fuel pressure? It drives beautifully when I first get in but after driving for a while, it feels low on power and then it starts to buck.

[NISTECH]

is your car california emissions certified and if so are you getting a check engine light on?

[Hubie]

The car was purchased in Florida by the original owner then sold to a second owner in Texas and now I'm the third owner in and still in Texas. So I don't think it's california emissions certified.

I bought the car last summer and this problem didn't occur until now. All I've done to the car is cat back exhaust.

There is no check engine light either.

Thanks for your help.

[Hubie]

Well it did it again today and this time I noticed that it would let me rev past 2500rpm(the reason for it bucking). But I still can't find the reason why it's causing it to into fail safe mode. Please help me. Thanks

[bvanfossen]

i'm having the same problem w/ my j30- i live in south fla! lol. i was wondering if you found the problem yet??? i'm trying to find a solution

--thanksBrian

[NateDogg]

2500rpm rev limit usually means MAF reads values outside of its spec and puts the computer into safe mode.

[portisroads]

do newer 240s have tendency towards vapor lock? it kinda sounds like that to me. with a full tank there is less vaccume in the tank. as you use more fuel and the pressure isn't equalized in the tank it makes a vaccume. just an idea. may not be right. im not sure if driving for an hour would effect it though.

[s13sr20chris]

i am leaning towards the maf myself. try cleaning the connector out with electrical parts cleaner.

[kickboxin]

did you find out what your problem was? I am having the same problem with my s13. I have swapped MAS and still having problems.

[ralphdig]

"these 95+ deg. temps here in Texas"Maybe your water is runing to hot, and this kick the safe mode, check your thermostat and your fan.