stuttering/bogging under moderate to heavy acceleration

[notsonic]

im trying to diagnose a problem on a friend of mines car.

its a 2000 3.8 firebird ~118k on it.

car runs fine under light throttle and idles normally.

but if you hit it kinda hard at idle or even a little at speed itll start to stutter. it feels a bit like a misfire or something. the exhaust doesnt smell like excess fuel like a non firing cylinder would though.

already replaced the fuel filter. replaced the air filter and checked the intake for any problems.

it was getting a misfire on cyl5 according to an engine code, replaced that and it hasnt come back. no other codes.

im not noticing any vacuum leaks.

thoughts?

[Rob Bell]

Re: stuttering/bogging under moderate to heavy acceleration

Check fuel pressure while driving it. The pump may be going out. Therefore, there's enough pressure for gentle driving, but as soon as the demand goes up, the pressure drops too low. Since there is no gas odor, you know it's not running rich, and you are probably OK with spark on all cylinders.

[whitdog54]

Re: stuttering/bogging under moderate to heavy acceleration

Is your car stock? I had a similar problem. it was my pacesetter headers. Went it, re-torqued the headers and y pipe, problem went away.