2.5 wont go above idle

about the middle of last week i tried some lucas fuel system treatment (with half a tank) and had a bit of a studder when i first ran the truck with it in, but it went away. truck sat over the holiday weekend and was started up tuesday to go to work, got to work fine. had to leave work late morning and when i went to start it, it loped so bad it almost stalled before i shut it off. tried a couple more times and got the idle to smooth out. got down the road, bam. i managed to get into a gas station, filled up with a full tank, ran fine. got a mile up the road, next light, bam. couldnt get the truck to get past idle without it shuddering, stammering, loping really bad. got the truck running by reving the hell out of it, shutting it off, trying to get slugs of vacuum to blow out something glogging the fuel line. got it back to work, left work, got home fine. put a new fuel filter in it, ran fine. went to work this morning, no problem, leave work and it started all over again.

so far, new fuel filter, checked out the coolant temp sensor, MAF, and put a fuel pressure gauge on it. air filter isnt new, but isnt what id consider dirty. fuel rail shrader read 67 pounds when idling, reving, loping. shut the truck on and releived it, put the key in and just turned the car on. fuel pressure hit 60 but i watched the need steadly drop to about 20-15 pounds...

so far im inclined to beleive that ive gunked up the screen in the tank, or killed the FPR, but i cant really make heads or tails of things yet. this is my daily driver, and sorry for the long post, but i figured id just put it all out there.

i cant find a return line for the fuel rail, is there one on the 2.5? does the high pressure indicate a bad regulator, along with a steady drop in pressure when the trucks off? or am i looking more at a new fuel pump/sending unit? or am i even in the right ball park? i did a turne up when i got the truck at 80k miles, it has 120k on it now, span of about 2 years. new plugs, wires, pcv, oil, filters on that tune up.

anyhow, the it seems to get worse as each bought hits, and to get it home this last time i followed a semi going 30ish and left in either first or second to keep the revs around 2-3000. when i could get em that high, and keep em, the truck would stay running.

I'd definitely check the in tank screen.

nuts.....

how hard is it to pull the tank on something like a 98 std cab 2wd?

its easier to pull the bed.

double nuts...

i pulled the MAF just for grins and didnt get a code, or change in truck idle. i happened to have one sitting from another engine and wapped it in. dont know if its coincidence or what, but its running now. i pulled the shradder pin and flushed about 2oz of gas...i seemed to have plenty of flow each time i cycled the key.

fireguy12117 said:

i cant find a return line for the fuel rail, is there one on the 2.5?

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There isn't one on a 2.5.

does the high pressure indicate a bad regulator, along with a steady drop in pressure when the trucks off?

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No, that's normal pressure for a "returnless" system. You'll actually find the return coming off of the fuel filter and the regulator is in the fuel tank.

update-

it wasnt the fuel system at all. i had swaped in a used MAF for no particular reason at the same time i had flushe gas out the fuel rail by the test port. truck ran fine all week, so the other night i put the old MAF back in. leave for work the next day and the truck dies at the end of my street. i had the one i had swapped in with me, put that back in, and drove the rest of the way into work.

no check engine light, and according to haynes and chiltons, it tests ok with an engine running voltage test....

bumpity...

anyone have any thoughts about the MAF being bad?

fireguy12117 said:

anyone have any thoughts about the MAF being bad?

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Only that it is odd that the computer didn't throw a code for it.