My 91 F150 is hard starting. When I can get it to start I have to have the idle up for it to warm up or it wont idle. While doing this the rpm is not stable (up and down some). Even after it warms up good it doesnt run good. The code scanner gives a #12 saying that the computer cannot raise the idle. I have done some research and so far I have learned the fuel filter, air filter or the tubes may need cleaning. It hasnt been that long ago when I cleaned out the tubes when I put on a new bypass valve. Anything else I should look at. Thanks...chuck

 

Might try pulling those intake tubes and inspect the throttle body butterflies. They get gummed up over time. Check to see if they open/close freely, and to see if there is a lot of brown or black junk built up on/around them. A good dose of throttle body cleaner might be all you need to get back in action.

 

Thanks I will try that. It hasnt been that long ago that I did that. Anything is worth a try..chuck

 

Could also be as simple as checking your battery cables. You may have a loose connection, or a corroded ground cable. You may have to peel back a bit of the insulation to see if the actual wire is corroded or not.

It would also be prudent to check fuel pressure - you might have a weak fuel pump or faulty regulator.

 

Thanks for that info. I did spray out the tubes yesterday and I was able to get the truck to start and run good last night. The battery never seemed to be an issue. I have always had good cranking. I was led to thinking it was fuel. I had a fuel pump replaced and it didnt help. I have two tanks and when I was having the problems neither tank would make it any better. The fuel regulator might be a option. I dont know what else would make the computer not be able to raise the idle...chuck

 

Typically the regulator is an easy check by pulling the vacuum hose - idle should increase, and it should be dry. If idle doesn't change, or if fuel comes out of the hose fitting, it's a goner.

Have you cleaned/replaced the IAC valve? It doesn't usually post a code, but controls engine idle in some situations.