williscr3

ive been dealing with an issue for 3 or 4 weeks now. ive been searching the forums going through the FSM ive tested just about every sensor and all are testing out good. it all started last month i ran out of gas or was very close to running out of gas. it started bucking when i stepped on the gas sputtering with no power and jerking so i pulled into gas station filled up and it continued to sputter when i left. then magically cleared up half way home. i can burn through first gear no problem. 2nd gear 2000rpm then at half to full throttle it would sputter and jerk. light throttle no problem but half to full throttle sputters and jerks specially if im lugging along at 1500rpm and then just push the gas down to half. now sometimes it seems to clear up and not do this at all. ive driven it 4 days now no problem now today its idling at 1100rpm and sputtered and jerked going up a hill then at top of hill it was perfectly fine. just seems like half to full throttle it does this. i sprayed the crap out of the vacuum lines with carb cleaner and i read some people use water to find vacuum leaks. i clamped off the vacuum lines at the intake to prove that it wasnt the line at all and no difference for every one. could my tps just be bad causing high idle and sputtering with jerking? i had no dead spots using meter though. pulled spark plugs and they are perfect looking. im getting tired of this truck now... im out of ideas. i cant test the fuel pressure with my tester i guess i need some banjo bolt deal. im so frustrated with this. plugs,cap, and wires are new. coil primary and secondary tested out good. i really am running out of ideas... ive never had a fuel pump work great then not work great so im hesitant about even worrying about testing it. i did change the fuel filter and run 2 bottles of fuel injector cleaner. all 4 fuel injectors tested out good too. any ideas?

RJR

Sure sounds like a fuel flow problem. Running well at low rpm/low power and stumbling when you ask more from it is pretty characteristic of fuel starvation.

My guess is you picked up some debris from the almost empty tank and it either lodged in the pump or in the filter.

williscr3

i agree but to come and go has me second guessing. seems like it does it more up hill then on flat ground. so your thinking the prefilter in tank may be clogged up? i did change the one fuel filter on motor. supposedly the pump was replaced a few years ago with the tank because the back end was hit. i bought the truck off my father-in-laws neighbor so i do know a little history of the truck and he told me about this the other day. i bought the cap, and wires from autozone they seem like cheap garbage so im going to run down napa today and replace them with something of better quality.

williscr3

tested the tps again all in all it seems ok but testing IDL and E2 with .57mm feeler it says i should get 2.3k or less and i get nothing. if its just sitting there no feeler i get 170 ohms. im still wondering if the tps is the problem. everything else is within spec. VTA -E2 was 5.1 at full throttle.

RJR

The IDL vs E2 measurement only affects how the ECU detects that the throttle is completely closed, and therefore only affects idle performance. For all other operating conditions, the important parameter is the voltage at the VS terminal. I would suggest testing it as follows. To do this you will need to have a long, very fine tip voltmeter probe so you can back-probe the connector while it is still on the TPS. Resist the temptation just to poke a sharp probe through the wire insulation. That will work, but will compromise the long-term health of your wiring by allowing moisture into the wire jacket.
- turn the ignition to ON, but don't start the engine.
- Ground the low lead of your multimeter to the low side of the battery.
- Check VCC - should be 5 volts
- check E2 - should be 0 volts.
- Check VTA, while you slowly move the throttle from fully closed to fully open. The voltage should smoothly and steadily increase from 0V to 5V, with no jumps, skips, sudden returns to 0 or 5V, or other monkey business.

If this is all in order, you can do these same tests at the ECU in the cabin. Once again, you need to do it with the plug inserted in the ECU, because the ECU provides the 5 volts and ground to the TPS. You should expect the same results.

If you can't back-probe the connector, you can also get some of the same information by doing a resistance test from VTA to VCC, and from VTA to E2, on the TPS terminals with the connector unplugged, while you slowly sweep the throttle from closed to open. Once again, you're looking for a smooth resistance change from min to max (or max to min, depending on pins and direction), with no gaps or jumps. You can do this same test at the ECU plug (on the wire side, not the ECU side) with it unplugged.

kcaudill

Had the same problem. It was the intake tube had a hole between the air box and the throttle body

williscr3

checked the air intake tube no cracks or holes.

back probed the tps 5 volts on VCC 0 volts at E2 but VTA i was getting .53volts closed and 3.68 volts wide open. no big jumps or any funny business while slowly turning it. why only to 3.68 volts though? normal? bad?

RJR

3.68V may be OK; I'm not sure how far the throttle can turn the TPS shaft. It probably doesn't go all the way to the physical end. I'd say based on what you've measured the TPS is OK.

williscr3

the problem with this is how its intermittent though. sometimes its ok, sometimes its bad. this is killing me. i hate to spend the money on the stupid banjo bolt for the price im almost at a fuel pump not to mention i may have decent fuel pressure just cant keep up with supply under a load. i dont want to just throw money at this stupid thing. the more i read about this on other posts the more confused i become as to my next step. now im seeing bad grounds causing this. i checked the coil, primary was .60 warm and 13.2 on secondary, but again with it being intermittent this is just making it a big problem. this motor has way to much going on with all these sensors its driving me insane! is it possible the fuel pump can act funny like this? i guess it is possible i over heated the fuel pump while running very low on fuel?

williscr3

finally figured the bucking problem out! turned out ive been leaking coolant from back of head at bypass. every time i worked on the truck, changed the plugs, gapped the plugs, changed the wires, changed the wires again, changed the cap, checked electronics, every time i would add coolant thinking it was because i had drained it maybe i was removing a bubble each time. finally this time i let it go! it started bucking soo bad as soon as i started it up. i stopped off the highway added coolant and bam instantly gone. so im assuming that the temp was reading hot on sensor and retard timing causing truck to buck. either way to those having similar problems this was my solution.

Schnayke

iTrader: (1)

I'm having odd issues with idle speed and what not. So many of the post's about that end up being the air in the coolant lines. I guess it is time to jack my truck way up and run it for while.
Glad you got it figured.

williscr3

I too am having idle issues so maybe that's related too. I'll keep an eye on it since I filled it up now.