I have been slowly getting the 1990 4.9L F150 I got back on the road. I have a emissions/vehicle inspected and everything too. BUT I pulled codes from this truck which after starting you need to keep pressing the throttle or else it stalls. After a while it will idle fine on its own. The codes I got.

Cold KOEO
21 Engine Coolant Temperature sensor out of range
24 Intake air temperature sensor out of range
26 Transmission oil temperature sensor out of range. Since the other part of code 26 is about MAF and my truck has a MAP

After driving around the block a little to warm it up.
KOEO 11 System OK

KOER
41 System lean
33 EGR did not open/respond during test
25 Knock sensor not tested

I enjoy working with electronics and sensor's but when it comes to all this I am stumped on where to start first. Does anyone have any idea's?

 

[QUOTE=4.9LOldFordTruck;15868038]I have been slowly getting the 1990 4.9L F150 I got back on the road. I have a emissions/vehicle inspected and everything too. BUT I pulled codes from this truck which after starting you need to keep pressing the throttle or else it stalls. After a while it will idle fine on its own. The codes I got.

Cold KOEO
21 Engine Coolant Temperature sensor out of range
24 Intake air temperature sensor out of range
26 Transmission oil temperature sensor out of range. Since the other part of code 26 is about MAF and my truck has a MAP

After driving around the block a little to warm it up.
KOEO 11 System OK

KOER
41 System lean
33 EGR did not open/respond during test
25 Knock sensor not tested

I enjoy working with electronics and sensor's but when it comes to all this I am stumped on where to start first. Does anyone have any idea's?[/QUOTEsee

Codes 21, 24, 26 can be disregarded if the test was performed when the engine was cold. In order to validate those, the same test needs to be performed after it has reached operating temperature and then shut off.

The code 41 is your main concern. It could be just a vacuum leak due to broken nylon vacuum lines that by this time are due to be replaced, probably. There are numerous posts highlighting the problem with these nylon lines becoming brittle and have small cracks you cannot see.

Code 33 can also be related and has been in the past to the above problem with broken vacuum lines and/or disconnected lines.

 

Codes 21 24 and 26 did go away after I warmed up the engine and testing again. So to start off check all the vacuum lines which I can understand now. The KOER I did today after driving around to warm up the engine. Thing is yesterday is when I called and scheduled my inspection which was set up for friday. I need to get to working on this then. Also I looked around a little to try and learn more about code 41. Some places talked about the HEGO sensor with that code.

 

Yes an old, aged O2 sensor can cause problem relating to be code. If its been 5+ years since it was last replaced, it may be worth the money to replace it.

I'm still going to say that broken/brittle nylon lines have a their part in the problem. Even a small vacuum leak can create havoc in these older trucks and create a domino effect on sensors, when it says its points to O2 sensor, its really just a vacuum leak.

 

I can understand that. Since it was my father's truck I wouldn't know what all work he had done on it. Top it off the truck has sat in the driveway for a good 3 years till I got it to work on.

 

Well I found out why the EGR wasn't doing anything. Looking at the vacuum routing sticker their isn't a vacuum hose going from the EGR to the engine vacuum reservoir. The sticker said EVR its hard to read from where it is located under the hood. I can see the obvious hoses that are on top of the intake and where they go. Even with a step stool they are a pain to reach.