First, I want to start saying that I have a 1998 F250LD with 5.4 that I bought new in September 97, and I've have 110K flawless miles on it. The only maintenance has been the fluids, tires, brakes at 60K and a new battery 1 month ago.

The check engine light came on about 6 months ago, but it had been running OK and when it was checked then it indicated a slow O2 sensor.

Recently, it has been "bucking" for the first 5 minutes when cold, but smoothing out. Also, it has an intermittent miss at idle. Sometimes smooth sometimes a little rough, sometimes comes and goes.

I took it to Autozone two nights ago and found the following error codes:
P1151 - What is it?
P1131 - What is it?
P1451 - What is it?
P0133 (#1 O2 sensor) - Which one is #1?

Since the P0133 was the O2 sensor, I bought one and installed it after asking several times which one was the #1 sensor.

Went to work next day and after about 15 minutes of driving the check engine light came on. I went to Autozone after work, and it had a P1131 code. They didn't have the code description, but one of the sales persons said it was the MAF sensor. I bought one ($140 including core charge) and the CEL came back on in 15 minutes. I disconnected the battery, again, to reset the error codes and went to work this morning. The CEL came back on after about 30 minutes.

It still has the intermittent rough idle. The engine seems to be more powerful. I'm planning to install a set of MotorCraft plugs per most opinions in this forum, but I'll have to do it when I have time, and can lay on my belly for a few hours.

I take it back to Autozone, again, and get the codes read again. This is getting tiresome.

Anyone have some pointers?

This is a lot different than working on my 51 Ford truck and 64 390 Galaxie.

Ken McWilliams
Dayton, OH

 

I took the truck back last evening to Autozone and had the codes read again. They were P1131 and P0133 which indicated a MAF and O2 problem. I told them that I just replaced both. He cleared the errors with his code reader and said that removing the battery cable doesn't erase the old codes.

Went to work this morning and the check engine light came on again.

Hmmmm, this is really getting tiresome and expensive after replacing parts and still getting error codes.

Ken McWilliams
Dayton, OH

 

P1151 Lack Of HO2S21 Switch - Sensor Indicates Lean
P1131 Lack Of HO2S11 Switch - Sensor Indicates Lean
P1451 Evap. Emission Control Sys. Vent Control Valve Circuit Malf.
I would look for a vacuum leak. Possibly the PCV hose, especially near where it connects to the intake. They are known to crack and get a vacuum leak.

 

If it comes on at idle or at least low load, I'd suspect a vacuum leak. If you clear it and it comes on under load, I'd suspect a fuel filter or pump. There are tons of possibilities but these would be where I'd start.

Some scan tools can read the freeze frame, the conditions the code was set under. If the one they use can read the freeze frame, that is what I'd use next to narrow it down.