You stated earlier the O2 sensor is fairly new, they generally last quite a while. If all the plugs are firing the coil is fine, what do the plugs look like? Unless they're soaking wet and black the coil isn't suspect IMO.

 

It says it will cause a HEGO code.

 

Conanski - see my earlier post (9:42 am) about the plug conditions.

The 02 sensor was installed in November. So it probably only has 1 - 2000 miles on it.

The coil has never been replaced since new.

 

have you every look at the TPS sensor. mine went out and it sent my truck all which ways but the right one. replaced for 35.00 and its fixed

 

A good computer will return a specific code for each sensor that is out of range, you're not getting any of these codes and the engine is definitely not running right so the computer is the big suspect IMO.

 

TPS has not been changed. Is there a way to check it to see if it is good or not? Or do you just go by the code for that?

Were your symptoms the same as mine when yours was bad?

 

I'm going to look into a computer and see what I can come up with.

 

I like to avoid blaming a computer but yea maybe in this case the computer is the culprit.

Be nice if it had a symptom or two common to a bad one but I guess ya can't have everything.

I sure hate to see ya buy one, even just a used one for 45-50 bucks only to find it does the same thing still.

Keeping a good thought for ya..........

 

Well here's what is going to happen to my truck:

Plan #1. I bought a new TPI (Throttle Position Sensor) and a new coil tonight. Tomorrow I am going to install them. If this doesn't solve the problem I am going to plan #2.

Plan #2. I am going to buy a reman computer and install that. If that doesn't solve the problem and no one else figures it out I am going to go to plan #3.

Plan #3. Take it to a Ford Dealer and let them diagnose the problem. I will send along a list of each and everything that was done to the truck. If this fails to fix it then I am going to plan #4.

Plan #4. Buy a keg of beer and light it on fire with all my friends and say good by to it. Clean up the mess and sell the scraps to the junk yard and use the money to put a deposit on a brand new Chevy. If that don't work I am going to plan #5.













Plan #5. I'm not really going to buy a Chevy. I am going to figure this out so that we can all learn something and become wiser men. So, What do you think about that?

 

Myself at this point I'd skip #1 and go to my local junkyard and pick up a used computer for the test. Take your computer with you so they have the numbers off it.

Other then that the only other thing I'd do is take it to a dealer (totally goes against my grain to even suggest that), but one of the mechanics there will or should have a, what's it called? a "brakeout box" for this series truck still.
They can connect it to the computer (connects between the computer and the truck harness), run it in the window on the seat and watch the different sensors in action while the truck is driven. Doing so should lead to the exact cause of the problem.

Before I ever took it to a dealer though I'd call around and find an independent shop with a mechanic with that same box and have them do it, should prove faster and cheaper. I'd be there with them while it was done, tell them that is all you want them to do, say 30 minutes of their time and that box.

If the O2 sensor is switching back and forth like it should be as shown by the box, flashing green/red green/red green/red the whole time but is still throwing a lean code I'd then go by a replacement computer at the bone yard.
If the o2 sensor is not switching and is going full rich, reading 9 or 10 and all "red"? continuously you probably have a bad sensor? (trying to remember how all that went)

However the guy monitoring those readings will or should be in a better position to make suggestions what to do based on the findings.

 

heated exhaust gas oxygen i think. it's the 2nd O2 sensor, farther back in your exhaust. look around your y pipe

 

My 87 F150/302 is having the same syptoms - except the engine light does not come on. However, I have found that when running cold, first thing in the morning when cool, it seems fine. Only when driven for a while do the syptoms show. Have you seen the same? Maybe another piece of the puzzle.

 

Did you at any time when you were replacing the right side manifold take off the tad/tab solinoids and connectors? The plugs for each solinoid look the same but they have to go to the correct one. I reversed mine during the rebuild of my 1988 F250. I kept getting the lean condition code and tried everything (including a second O2 sensor) before I stumbled upon the reversed tad/tab connector. I consulted a schematic to determine what went where and found I had the two reversed. Once corrected - no more lean condition.

If the connectors are reversed too much air is put into the exhaust manifold upstream of the O2 sensor. The O2 sensor then sees a lean condition and the computer dumps in more fuel to compensate.

Just a thought

 

chas87f150 - It does run good for the first 2 -5 miles when it is totally cold. After that the symptoms start and just keep getting worse.

 

jamini - I wasn't there when my buddy changed the manifold. But I am going to take a look and see if there is in fact sensors in there that may have been crossed.