I have a 96 F-150 4x4 5spd 4.9L 144k. Runs fine of the morning but once the temp gets up on the engine and you shut it off and let it set for 10-15 minutes it don't want to start back up. When it does start it thrashes and shakes and sputters. You hold the throttle about half way it still shakes like crazy but will eventually smooth out a little. I've replaced the cap rotor pick up crank sensor swapped the coil and ignition module off my 93. Nothing seems to help. It set a few codes, P1131,P1151,P0136. Which are all HO2 codes. Could it be EGR related or maybe a clogged exhaust?

 

Forgot to add that when it does smooth out a little it's very under powered and hesitant to throttle response.

 

I would start by replacing both O2 sensors, they aren't that expensive. If it were just the 1131 and 1151 I'd say it's something else, but the 0136 is pointing toward a failed sensor.

Yes, it could be EGR, it could be a clogged cat. Could be dirty or leaky fuel injectors.

 

The truck sat for almost a year. But running like this is why he parked it. I may try the O2 sensors. There are two up stream. One on each manifold and one down stream after the cat. It's about $170 for all three if them. For some reason I keep thinking its a coolant temp sensor bad but I hate to keep throwing parts at it. Thanks for your input.

 

Okay - the P0136 is the downstream sensor. All that does is report on cat efficiency. Causes:

Faulty O2 sensor
Leak in exhaust close to O2 sensor
Short to voltage on O2 signal circuit
Open in circuit resistance caused by corrosion in connector

The P1131/1151 are lean codes, possible causes:

- Faulty Oxygen Sensor
- Vacuum leak
- Fuel injector problem
- Check for cylinder misfire
- Engine mechanical condition

Maybe it's low fuel pressure? I'd change the fuel filter and get some fresh gas.

 

Ok I'll try that this weekend. Thought about pulling the top half of the plentum and checking all those stupid vacume lines. Thanks!!

 

It was the fuel pump!!! Only carrying 20lbs of pressure after getting warm. Replaces the filter first, no change. Put a new pump in it and it runs like a champ!!

 

Now clear your codes and see if any of them come back.