4.6 gurus ?

[JFD]

After a major maintenance on my wife 4.6 D2 I'm getting a few bugs.
Basically I disarm all the top part of the engine less the heads.
Did not want to change the head gasket as the truck has only 40 K miles
so I guess that can wait a little more. All parts were cleaned very well, all
gaskets and o-rings are new, injectors cleaned, new spark plugs and wires,
exhaust manifolds wrapped, engine harness got hi-temp sleeving, new valley
gasket, new valve cover gaskets, etc...

1. Engine won't hold rpm on first morning start. Before that maintenance
when you cold started it, it will climb to 1,500 rpm, stay there for 30 s and
then level around 800 rpm. Now you have to do it with gas pedal.
2. Coolant circuit is getting pressurized really quick, much before engine will
warm up. If you run it for a couple of minutes it will build up some pressure.
3. I'm getting codes P0130 (02 sensor circuit malfunction) and P0171 (too much
02 in exhaust).

Other than that it's running real smooth

Thoughts ?

 

[The Fourth Amigo]

Pressurized cooling system............... Maybe you should have replaced the head gaskets.

 

[wheelen disco]

Make sure you purge all of the air out of your coolant system. And why did you tear it down in the first place? What were your symptoms?

 

[JFD]

Make sure you purge all of the air out of your coolant system. And why did you tear it down in the first place? What were your symptoms?

A few small coolant leaks, valve cover gaskets leaking, valley gasket leaking, random misfire.

 

[wheelen disco]

You need to do a compression test and check for exhaust gasses in the coolant

 

[Chris740]

You need to do a compression test and check for exhaust gasses in the coolant

Do this first..My bet is headgaskets as well.