acts like its running out of fuel

[baddis]

i have an 88 ranger with a 2.9. it acts like it is running out of fuel. first thing i did was replaced the fuel filter (yes it was clogged) it ran great for about 15 miles and went back to what it was doing. i pulled the filter and replaced it again and no change. checked fuel pressure and it was 35 psi at idle but crack the throttle it dropped to 10. so i replaced both pumps and the in tank sock. now the truck runs good in the mornings on my way to work (30 miles) except for the last 2 miles. truck sits all day at work and go out and it spits and sputters all the way home. go out the next morning and it runs fine. i have checked the codes and the code reader says there is nothing wrong. anyone got any ideas? oh and i have replaced the pumps again and it still does it.

 

[CraigK]

try disconnecting the O2 sensor

 

[Wicked_Sludge]

what? no. leave the O2 be.

sounds like a bad fuel pressure regulator to me...

pull the vacuum line going to the regulator. is there fuel in it?

 

[baddis]

what? no. leave the O2 be.

sounds like a bad fuel pressure regulator to me...

pull the vacuum line going to the regulator. is there fuel in it?

no there isnt i plugged the line off and reved the engine a little bit and got no fuel coming out of the regulator

 

[Wicked_Sludge]

interesting. would it be possible to take your fuel pressure gauge with you to work and check the pressure while the truck is acting up? this way we can at least rule out or pinpoint fuel delivery as the problem.

 

[CraigK]

A bad O2 sensor can shut off fuel to the injectors. (Learned this from having a bad sensor myself - you don't want to know the stuff and $$$ I did to this vehicle to try to fix this problem before I simply disconnected the sensor and the problem instantly disappeared!)

Disconnecting the sensor takes about 30 seconds (okay, maybe 90 seconds), and if the problem is still there after running for a day, takes another 90 seconds to hook back up. Might be the problem, might not. But it's an easy check to rule it out.

CraigK

 

[burnsroseburg]

I pulled my o2 sensor and it helped tremendosly. Is this just a temp. fix or do i really need a new one. Will it harm my engine to just leave it for a while?

 

[burnsroseburg]

did you try pulling the o2 sensor? I did yesterday and it helped tremendously

 

[Wicked_Sludge]

it wont damage the engine in the long run, it'll just lower power and fuel economy. id get it replaced sooner than later.

i guess good call on the o2 sensor craig. ive never seen an o2 cause such a lean condition as to cause driveability problems...even on an EEC-IV vehicle.

 

[Psychopete]

I pulled my o2 sensor and it helped tremendosly. Is this just a temp. fix or do i really need a new one. Will it harm my engine to just leave it for a while?

You may replace it, and the problem could still persist (but usually it being bad can be the case, but don't get too pissed off if you replace it and the problem didn't resolve). The engine is staying in 'warm up' mode since it's not present. However, if it hasn't been replaced that you can recall, it certainly wouldn't hurt to replace it. You might pull codes and see if you have anything in non-volatile memory after o2 replacement (or reconnection).

Pete

 

[CraigK]

Psychopete is right. The problem may be helped or eliminated by disconnecting the O2 sensor, but that may not be the problem, or the entire problem. But it's a big clue. (Fuel flow to the injectors, as determined by computer control based on sensor inputs.)

You can run indefinitely without the O2 sensor. I ran ~10,000 miles (rough estimate) before I eventually replaced it. Gas mileage for me was 16 mpg with the O2 sensor disconnected, and 17 mpg with a new unit installed! (I take VERY accurate ACTUAL mileage readings.)

I would recommend:
Check for exhaust leaks that might be causing faulty O2 readings (air getting into the exhaust through an upstream exhaust leak - such as the manifold-to-Ypipe joint). If your exhaust system is without any leaks, try replacing the O2 sensor.

CraigRK

 

[Wicked_Sludge]

for that matter, its easy enough to back probe the O2 sensor to "see" what the computer is seeing. the engine needs to be up to operating temp. to do so. less than 0.4 volts is a lean mixture, greater than 0.6 volts reads rich. ideally, the voltage should cycle back and forth every second or 2 (this can be hard to see on a digital meter, so if you have an analog one handy it might be better to use it).

if the PCM is really cutting the injectors because of the O2 signal, i would expect the O2 to be pegged somewhere near 1 volt.

 

[baddis]

ok i did a fuel pressure test and have 30 psi at idle. crack the throttle and it jumps up to around 35 psi. i let it warm up and the fuel pressure gets flakey. hold the rpms at 2k and you can watch it drop and rise. i tried unplugging the o2 sensor as suggested and the only thing it did was make the exhaust smell like crap.this truck is beginning to irritate me to no end. oh and before someone says tfi module i have tried 6 different ones off of running trucks. i have checked the grounds by the computer and on the radiator support also.

 

[IMenriched]

On another form...they were having simular symtoms. they discovered that the pins on the engine computer (ECM?), inside the cab right side of the passager side. ANYwho....the pins on the main harness connections were less than consistant...thinking it was #59 & #60...were the main culprits.

can't say for certain what those pins do...or if they were the exact pins....but you prolly get the idea....took the connection apart and resecured the wire to the pin and in the connection block.... things improved.

not sure if you've been down that trail or not...considering the amount of issues your having...might be worth a shot.

 

[baddis]

i hadn't gone that far yet i was hoping for an easier solution. i don't suppose you remember what forum it was from do you?