Help! Car sputters under 3k rpm!

[boiracersxt]

My car started sputtering under 3k rpm. It was running fine before on my 96 240sx. I pulled the motor and transferred it to my 95. I would give it light throttle and my wideband would read max lean. The weird thing is, once I pass 3k rpm and under boost, A/F is 11.7 and it runs fine. It does it sometimes. It doesn't make sense how it bogs, sputters and make no power at lower rpm. Any ideas? I'm not throwing any major engine codes. I'm running a JWT tune, 72 lbs, and z32 mafs. Any ideas?

[spooled240]

check for vacuum leaks. an air leak in the intake can cause your engine to run lean, is your spool normal?

[Florida240sx]

Vac leak, Checked your plugs? What's the gap? Just fill up on gas? When was last time fuel filter was changed?

[spooled240]

hey boiracersxt, I have the jwt tune w/ the z32 mafs as well but I don't have a wideband. What are your afr's across the board and what's your mileage like? Mine is pretty bad, probably around 20-22mpg on highway..thanks man, i just wanna know if my engine isn't running abnormally rich for whatever reason..

[boiracersxt]

Plugs are kinda whitish, New fuel filter. Plugs have been gapped down to 025. Vac reads 20. I already went through all my pipes, everything looks secure. My JWt is bad on gas. Right now, my ar are 10.7! It runs super rich under boost and lean off. I think it might be my tune.

[spooled240]

you know this is kind of what i expected with your problem: I think that you have an air leak (vac still reads 20?)

Because i think that when your engine is in vacuum, it's sucking unmetere air through some leak or whatever and making the engine run lean at vac.

When boosting, the boost is probably leaking out the leak creating less air in the engine thus making it run rich under boost.

I know you checked for air leaks and what not and your vac. reads 20, but try again to find the slightest leaks..maybe a blown/cut coupler, blown gasket somewhere? I think that there is probably a small leak somewhere that doesn't affect the reading of the vac gauge but greatly affects the driveability of the car.

[boiracersxt]

The only leak there would be is in my intake manifold. I'm using a plastic gasket. I used gasket maker for my lower intake because I didn't have a gasket. Could I spray something there to show me it's leaking?

[480sx]

Take starting fluid and spray a tinyyy spray of it near the area where you think its leaking. I would say do it all around your DIY intake manifold gasket.. If you hear your idle go up you'v found your leak.

[spooled240]

man i would just re-gasket the intake manifold, don't risk the lean condition when idling man you could mess up ur eng if the leak gets worst

[boiracersxt]

I doubt it's a leak. I just put the gasket in 500 miles ago. Everything was tightned down correctly.

[driftMachine]

boiracersxt, did you get this problem figured out after? I'm interested because it sounds exactly like the problem I'm having. I have my car put away for the winter now so I can't take it out, but was hoping to see what the issue was with yours so I can see if it's my issues as well. I believe mine is a air leak somewhere. I'm going to visually go over everything before I take it out again in the spring.

[Florida240sx]

Tune is probably rich. How old is the gas.Possible problems: Bad gasSpark plugsSpark plug wiresGround wireLoose connectionFuel filterVaccum leak

For vaccum leak it shows good vac but i've had a coupler completely off and it's been perfect vac before....Do boost leak test. but being you have diy gasket try sprayign some starting fluid around your intake mani. Do this when cold because it is explosiveish and don't want ot start a fire