HELP! 95 F150 5.0 Idle reving and power loss

[matsel92178]

I recently purchased a 4x4 1995 Ford F150 with a 5.0 and auto.

Hopefully someone here can make me feel like an idiot and help pin point a few problems Ive been having.....?

When Initially started, Idle fluctuates between 400 and 1500 RPM, as if you were tapping the gas pedal every few seconds - Also, after driving for 10-15 minutes, a substantial loss of power and acceleration is noticed. Also when reved up backfiring is present, leading me to believe fuel/spark management is being effected.

Some Info should be known - Has a 6" susp. lift and 35/12.50/15s on 15x10 rims. The Speedometer jumps around erratically when over 5 miles per hour and has not been recalibrated for the bigger tires. The truck is equipped with a smog pump and has smog-legal shorty headers, passenger side is cracked at flange and both are very rusty. I have replaced secondary Ignition(plugs, wires, cap, rotor), airfilter, pcv, cleaned throttle plate and iternal air-bypass vent(which I understand is a common idle problem in the 5.0) and added 3 diffent bottles of inj cleaner through gas tank.

This is where it starts getting weird.....

Last year of the EEV-IV control(Not OBDII), the 1996 and up are EEV-V(OBDII). So my Scan tool Data stream is very limited. At no time during the last 2+ weeks has the truck set a hard fault code. The MIL has not once came on unless I did something to make it come on(ex. disconecting a sensor). No codes in history. only soft codes pertaining to self-test procedures(like not hitting the brake pedal, or cycling the OD button, or reving the engine for a moment). Fuel Pressure sits at a constant 40psi. Regulator diaphram is intact and isn't leaking. have not pulled the upper intake yet to test the pass side 4 injectors but the drivers side 4 all ohm out between 15.2-15.5 and no gas is smelt when running. The only recurring code I get that I have yet to find an applicable flow chart is code 412(cannot control RPM during KOER high RPM check). KOEO test gives me a code 11(System Pass). I have tried pounding on the gas tanks while irractically idling, I have Tested both the IAC and the TPS, both were within specified range of resistance/voltage. Cleaned EGR valve(moves freely). If you disconnect battery or clear ECM, Truck runs better but soon emits same syptoms.

I am wondering if the exhaust leak at the header is causing the O2 sensor to act up? I am replacing the headers tomorrow with full length headers and collectors and am relocating the single O2 sensor about a foot and a half farther back in the exhaust. MN has no emmisions requirements anymore so I am running straight duals with no convertors into an H pipe where I am re-locating the O2.

As you can read I have a few problems going on here...but my main questions are this:

1) cause and repair of the idle and loss of power
2) could the O2 be reading wrong without setting a lean or rich code?
3) Is the sporatic speedo caused from a bad speed sensor in the T case?
4) Any known ways of eliminating the SMOG pump, cat and air tubes.
5) What does the DTC 412 reflect?

please make any and all comments or suggestions available to me through this thread or email me at matsel92178@yahoo.com

[landyacht]

That's some awesome questions you have there...

As far as your power problem goes, that sounds like something i've had to deal with on my own car (see the signature) and i have found there are several thigns with my car.

First, the surging and that is caused by an improper air-fuel mixture. In my case of the carbeurator, it's the vaccum hose that is lose or disengaged or it is the carbeurator needing cleaned.

Because yours is fuel injected, i am thinking the same as you, which is the O2 sensor is shot. A fuel injection flush at the same time may be a good idea to do aswell. By doing these two things you ought to find that the truck runs just fine.

The rest of the problems, i haven't a clue, perhaps another can answer those for you.

Good luck in your venture!

[gls1000]

Originally Posted by matsel92178

I recently purchased a 4x4 1995 Ford F150 with a 5.0 and auto.

Hopefully someone here can make me feel like an idiot and help pin point a few problems Ive been having.....?

When Initially started, Idle fluctuates between 400 and 1500 RPM, as if you were tapping the gas pedal every few seconds - Also, after driving for 10-15 minutes, a substantial loss of power and acceleration is noticed. Also when reved up backfiring is present, leading me to believe fuel/spark management is being effected.

Some Info should be known - Has a 6" susp. lift and 35/12.50/15s on 15x10 rims. The Speedometer jumps around erratically when over 5 miles per hour and has not been recalibrated for the bigger tires. The truck is equipped with a smog pump and has smog-legal shorty headers, passenger side is cracked at flange and both are very rusty. I have replaced secondary Ignition(plugs, wires, cap, rotor), airfilter, pcv, cleaned throttle plate and iternal air-bypass vent(which I understand is a common idle problem in the 5.0) and added 3 diffent bottles of inj cleaner through gas tank.

This is where it starts getting weird.....

Last year of the EEV-IV control(Not OBDII), the 1996 and up are EEV-V(OBDII). So my Scan tool Data stream is very limited. At no time during the last 2+ weeks has the truck set a hard fault code. The MIL has not once came on unless I did something to make it come on(ex. disconecting a sensor). No codes in history. only soft codes pertaining to self-test procedures(like not hitting the brake pedal, or cycling the OD button, or reving the engine for a moment). Fuel Pressure sits at a constant 40psi. Regulator diaphram is intact and isn't leaking. have not pulled the upper intake yet to test the pass side 4 injectors but the drivers side 4 all ohm out between 15.2-15.5 and no gas is smelt when running. The only recurring code I get that I have yet to find an applicable flow chart is code 412(cannot control RPM during KOER high RPM check). KOEO test gives me a code 11(System Pass). I have tried pounding on the gas tanks while irractically idling, I have Tested both the IAC and the TPS, both were within specified range of resistance/voltage. Cleaned EGR valve(moves freely). If you disconnect battery or clear ECM, Truck runs better but soon emits same syptoms.

I am wondering if the exhaust leak at the header is causing the O2 sensor to act up? I am replacing the headers tomorrow with full length headers and collectors and am relocating the single O2 sensor about a foot and a half farther back in the exhaust. MN has no emmisions requirements anymore so I am running straight duals with no convertors into an H pipe where I am re-locating the O2.

As you can read I have a few problems going on here...but my main questions are this:

1) cause and repair of the idle and loss of power
2) could the O2 be reading wrong without setting a lean or rich code?
3) Is the sporatic speedo caused from a bad speed sensor in the T case?
4) Any known ways of eliminating the SMOG pump, cat and air tubes.
5) What does the DTC 412 reflect?

please make any and all comments or suggestions available to me through this thread or email me at matsel92178@yahoo.com

Battery fully charged?
Charging system charging?
Fords will run like crap if the battery voltage
is not up to 14v or so when the vehicle is running.
If you have recently disconnected the battery recently
it may have to relearn settings, some surging is normal
for a little while.
Last, if all else fails, you can try truning the throttle body
adjust screw in about half a turn, sometimes this will stop
the surging.