My truck has had a rich condition code for some time. I have never been able to figure it out. I believe the code was 172. Its been awhile since i checked it.

Things i have done.

New plugs
ohm checked wires
cleaned cap/rotor
replaced cracked vacuum lines
fuel pressure 39 engine off 32 engine on
FPR doesnt leak when vacuum is disconected.


The truck started loping at idle. Moving from 600-850 rpm back and forth. Im hoping this may be a new symptom that can lead to helping solve my rich condition.

The truck runs rich, only get 10 mpg at best doing 55 mph. It cuts out some times under light load for a second, like it looses a cylinder or ignition gets cut.

But when you stand on the throttle it runs perfect every time. So when the truck goes to open loop it runs like a banshee. The check engine light only comes on after the truck is up to temperature and you are going 50 mph at least.


What could cause the loping idle?

 

I just sprayed either, carb cleaner, and contact cleaner over the engine and vacuum lines to see if the idle changed. It didnt make and noticeable difference in rpm. The truck wasnt looping at this point.

 

Sounds like the typical plenum gasket. Not as common on the 5.8 as the 5.0, but still happens. Try spraying carb cleaner just behind the distributor where the upper plenum and intake meet. Pay attention to both sides. I think you will find that the plenum gasket is bad.

 

I will try that. Thanks.

 

i have a 1994 e250 5.8 and it runs great until it hits operating temperature then it starts running rought.I replaced the map sensor and the tps. the feul pump relay and the air control motor on side of throttle body click back and fourth between each other making my idle bounce up and down with like a miss. any thoughts