Fuel starvation IN 5th GEAR ONLY???

[MIGHTY 8]

Hello everyone,
In a continuation of maladies affecting my car, I have succeeded in getting to this point.
Car absolutely drives like a bat-outta-hell, and pushes all the way to redline. But, get to the point of shifting up to 5th for highway cruise, and I get all sorts of instantaneous power loss, backfires, (from the engine bay) and related problems.
After a few minutes off to the side of the road.....absolutely recovers and screams up again through the gears.
This is all, after having been picked up from the shop!!
Car is a 2L, equipped with IDFs.
Love to hear your suggestions, please.

[Ken]

Do you have a mechanical or electric fuel pump? And are you running a fuel pressure regulator?

[sptcoupe]

Also, what is your jetting, particularly the needle valve size. Do you have cams, higher CR and a header? And hwat are the float settings?

[131]

Will it sustain 5-5.5K/rpm in 4th instead of changing in to 5th?

[azruss]

5th gear is where the fuel pump has to work the hardest. You are not in the sweet spot and your air drag and rolling resistance is high. I would first check the fuel filter to see if it is close to clogged. after that, sounds like a weak fuel pump. If that is the case, the problem will get worse with time.

[So Cal Mark]

yep, sounds like fuel starvation. Along with the good advice about the filter, check the quality of the hose from the tank to the pump on the inlet side. There is hose at the tank, near the left rear lower arm and at the pump. Cracks in any of those hoses will not allow the pump to suck very well

[baltobernie]

Maybe venting to your fuel tank is marginal. Try loosening your gas cap and see if the problem goes away.

[Kent124]

Maybe venting to your fuel tank is marginal. Try loosening your gas cap and see if the problem goes away.

That's a good thought.

[MIGHTY 8]

Thank you everybody for your wise and constructive advice.

Turns out, it was a fuel starvation problem as some of you had correctly surmised. Was told that there was some corrosion/"residue" in the check valve within the fuel system. Not really sure where this valve lies, but can guess that it lives somewhere underneath the car near the elec. fuel pump and the fuel filter.

Drive back from the mechanic's was uneventful, which is more then I can say after having fought this problem since May of '11.

Thank you all and happy safe driving.

ps

And yes....upon a test drive with the mechanic riding shotgun, as the car "died" after reaching cruise speed and in 5th gear, we pulled over to the side, he poped out and un-screwed the gas cap. Car then started right up, and off we went! We had already checked the fuel pump at this point, and could then continue on to pin point where to focus on how to fix the problem.

[124JOE]

i told christine to put a huge filter up bt the carb
it fixed her problem