OK I had a problem where my truck wouldn't idle at all for a little while. Just replaced the MAP sensor and EGR valve. It will idle now, but I still have a persistent problem. Upon startup it just stalls right out. RPMs climb for a second and when it goes to settle around 700 RPM it dips down low and shuts off. If I hold my foot on the gas for a minut e it will settle and do fine. Its not a operating temp issue. I can drive it all day, turn it off and when I go to start again it'll still do it. What could this be?

88 f150 Lariat 4x4 with 302.

Thanks,

 

Idle air control?

 

I'm keeping that in mind, but I have taken it off to clean and check it. Pretty sure it was replaced by the previous owner not too long ago. Clean as a whistle and not throwing any codes. Now that I replaced the egr valve and map sensor, the only codes it should be throwing is a power steering pump switch error.

 

So you've checked the codes recently? Are you just saying it isn't throwing codes because the light isn't on?

 

the previos owner of my newist f150 said it had a 5.8l....theres a big 5.0 stampted on the intake...check the IAC...and pull codes thats the quickest way to see whats up.

 

^ I had a guy try to tell me that I didn't have a 5.8, because ford never made one....

 

Possible vacuum leak, and maybe the computers are adjusting for it after start up? Long shot, but it can't hurt to look Ian's listen to the vacuum lines.

 

No I checked codes buy jumping the test connector. I did that because a week ago it wasn't idling at all. Stalled every time unless I had my foot on the gas. So I ran codes and it gave me errors for my egr valve' map sensor and power steering pump switch. Replaced the map sensor and egr valve... That's why I'm saying it shouldn't be throwing anymore codes than that.

 

I can't hear any vacuum leaks at idle, but there is a whining almost turbo charger sound that happens when taking off from a stop. Very well could be a vacuum leak, I just don't know much about checking for that. Guess it wouldn't hurt to start systematically changing all the hoses and clamps one weekend.

 

Yea, they probably need or are about to need replaced anyway. One of the few things I could say you can replace without checking on a truck so old. You can test them by carb cleaner around the hoses, but it doesn't seem to work for me well unless its a big leak, which is what I would think you would have, or several small ones. You can also hold a long tube to your year and have someone rev the engine up some and listen around