1988 ford bronco 5.8 efi

Upon start truck runs fine. Once it sits about 30 seconds, it starts sputtering pretty badly. Feels like a loss of power. Then when I slam the petrel I get a loud POP from the motor. It used to shoot flames from the throttle body but not it has stopped. When I pull the air box hoses from the intake, I still here a loud pop in the air box. This leads me to think its still backfiring from the intake because I assume the pop in the air box is from the oil vacuum line going to the box. I have changes the map sensor, tps, cleaned the throttle body, cleaned the iac. Changed the fuel vacuum thing that goes from the line to the fuel rail. The fuel filters and I sea foamed it twice. Once the motor is reved high or driving the motor runs fine. Could it be vacuum related? I do have one vacuum line on the passenger side of the motor that's snapped and I can't figure out where it goes. It's hard to establish the color but its a pinkish orange color.

Any help is appreciated.


And also motor has less than 85000 miles and was never driven hard by previous owner so I assume the timing chain should be fine.

 

that all sounds timing related. get the motor to operating temp, turn off motor and pull the spout connector and loosen distributor bolt, start motor and with a timing light set timing to 10*btdc. shut motor down. tighten bolt and put spout back in and start engine back up. see if this continues.

could also be a bad cap/rotor or bad plugs or plug wires.

have you changed the oil after doing the seafoam treatment? plugs should have also been changed.

 

Everything has been changed included plugs and wires. Everything was fine but after truck sat for a year all of this happened

 

Sat for a year ? Have you checked fuel quality and pressure ? Fuel filter , cap for moisture ? Wires for rodent damage ? Much can go wrong if a vehicle sits for a year .

 

Yes sir I have checked all of the above

 

Since it will run, albeit badly, Pull KOEO Codes first and see what the ECM "says" is wrong. NO misfire goes unnoticed with EEC-IV. There should be some indication of the problem there. Worst case scenario, try to run a KOER test. With both tests make certain it has reached op. temp. before testing.

I agree that it sounds like you are describing a timing issue but after having sat for a year, you could have a cracked PIP sensor or some other electrical nightmare that you will chase forever unless you get codes from it.