1999 5.0 Mountaineer rough idle, hesitation, backfire

[slowstang88]

I just bought this puppy for cheap because my neighbor was tired of throwing money at it to fix it. For starters, it has sat for 2 years so I topped off the tank with high octane and added 1/2 gallon of toluene (to raise octane), put in a new battery and cranked it over after cycling the key 5 times to get fuel to the injectors. Long story short, its doing the same thing it was doing 2 years ago when he parked it. Hard start, hesitation, stumbling, missing, and backfire through intake. Heres a list of new parts that he put into it:

o2 sensors
fuel pump/filter/intake sock
MAF
IAC
plugs/wires/coil packs
air filter
oil/filter

My next course of action is to check for codes, but are there any re-occuring problems that makes this sound familiar? Above 1500rpm its fine, maybe hung open EGR?

 

[Turdle]

First course of action is to scan codes, then post them back up here.

 

[slowstang88]

First course of action is to scan codes, then post them back up here.

Word, will do.

 

[slowstang88]

This took long enough but here goes..

P0113- Intake air temperature circuit high input
P1504- Idle air controller circuit fault
P1000- OBDII system checks incomplete
C1234- Right front wheel speed sensor input missing

I think the IAC code was from me unplugging sensors while running to narrow down the issue. I unplugged the MAF while idling to see if it would smooth out as well, idled worse. I checked sensor inputs/outputs/ranges while running and got nothing out of the ordinary. Theres a doggy spot between 2/3-3/4 throttle to full throttle where it doesnt pick up power. I payed close attention to the TPS voltages through the entire throttle range and it was all smooth. There may be a problem with the FPR, would that cause hard start and flat spot in higher throttle ranges and backfiring through the intake when its cold? I ran 1 quart of sea foam (for fuel injection) into the brake booster vacuum hose after filling the tank with 91 octane fuel and adding 1/2 gallon of toluene and a small bottle of fuel system cleaner. I dont think the seafoam is out yet because its still smoking a bit on higher throttle inputs.

 

[slowstang88]

This took long enough but here goes..

P0113- Intake air temperature circuit high input
P1504- Idle air controller circuit fault
P1000- OBDII system checks incomplete
C1234- Right front wheel speed sensor input missing

I think the IAC code was from me unplugging sensors while running to narrow down the issue. I unplugged the MAF while idling to see if it would smooth out as well, idled worse. I checked sensor inputs/outputs/ranges while running and got nothing out of the ordinary. Theres a doggy spot between 2/3-3/4 throttle to full throttle where it doesnt pick up power. I payed close attention to the TPS voltages through the entire throttle range and it was all smooth. There may be a problem with the FPR, would that cause hard start and flat spot in higher throttle ranges and backfiring through the intake when its cold? I ran 1 quart of sea foam (for fuel injection) into the brake booster vacuum hose after filling the tank with 91 octane fuel and adding 1/2 gallon of toluene and a small bottle of fuel system cleaner. I dont think the seafoam is out yet because its still smoking a bit on higher throttle inputs.

Oh yeah, there is also a code for fuel level sending unit out of range, the level gauge doesnt work.

 

[slowstang88]

Well I've been trying some things here and there and with the IAT high voltage code I checked them visually and ended up unbolting the coil pack mounts to get access. The one on the left with 2 wires(while standing in front of it) twists around where the plug goes into it. I'm assuming this is broken, no? I looked at the IAT with the scanner hooked up again and it said 82*C and I know the engine wasn't that hot considering I had just started it. PLEASE HELP!!!

 

[slowstang88]

Seriously guys, Ive searched this forum... I think the sensor I just posted is ECT after Googling it. Is the IAT part of the MAF?

 

[slowstang88]

Wow.. Thanks for nothing, I think I'll have better luck beating my head against the wall.....

 

[Rcb1126]

Wow.. Thanks for nothing, I think I'll have better luck beating my head against the wall.....

Did you figure it out having same sorta issue?

 

[410Fortune]

Yikes ooor dude back in 2012
Got no responses

I would have told him to first check fuel pressure
Just because it has new strainer pump and filter does not mean fuel pressure is good

Then I would have told him to check the firing order, make sure it is wired correctly

After that it’s verify all plug wires are good (visual inspection) and pull the spark plugs and have a look
The plugs can tell you which cylinders are firing and which are not