First off I want to say hello to everyone this is my first post in this forum. Ive owned about ten different F150s in my life and I am still in my 20s .

Anyways the problem I have been having is with this 89 F150 I just bought. It has the 4.9L engine, 4spd with overdrive, and 4x4. The issue I can't seem to fix is that when I start the truck up it starts rough and the idle goes up to around 2000 RPMs and then right back down to 500 RPMs or so and then stalls out most of the time. If I start it right back up it does the same but usually catches itself before it stalls and then after about 20 seconds idles fine. Everything is also fine when I am driving it and there is absolutely no problems other then startup. Even if I drive the truck for an hour or so and shut it off, it will do the same thing once I fire it back up.

So far after doing some research I have replaced the Idle Air Control, the Throttle Positioning Sensor, and all new plug wires. I replaced a few of the old vacuum lines that were showing decent wear. I also cleaned out the throttle body the best I could without actually removing it from the intake. Even after all of that the same problem is still present in my truck, and I really don't want to keep replacing parts that won't help it.

Any help from you guys or girls would greatly be appreciated. Thanks


Here is a link to a video of me starting it up. > http://youtu.be/1v5VF6WmcC8

 

I'm having this same exact problem actually with my truck, if u look on top of the intake manifold there it's the vacuum line tree or whatever, I pulled off a red line, with a 90 degree head and my truck ran just fine, it leads to something under the intake manifold, sorry for being short on names of parts, but I'd try that, if u find the name of that part that would be GREATLY appreciated

 

Edit: not the exact problem, but close, itll strt the sown to 500 and then choke

 

Yep I am stumped right now. Hopefully someone who had this problem before will chime in and help us out! Ill try taking that line off tomorrow and plugging it.

 

Definatly! Lol, it would let me sleep better at night, haha, keep us posted on what you find out!

 

Check for error codes.

 

I checked for the codes and all I got was code 67 which I believe isn't anything important, something about the neutral safety switch. Would you happen to know how long after I installed these new parts would it take for the computer to recognize the change? I really haven't drove it more then 10 miles since I put everything on so maybe that is my problem. I am going to reset the computer today and then try to put 50 miles or so on it.

 

Ok I just checked the codes again and I got a code 33. I believe it has to do with the egr valve. So I fired the engine up and pulled the vacuum line off the egr valve and the idle did not change. I also pulled the plug off the egr valve and the idle did not change. This would mean the egr valve has failed or perhaps its stuck right?

 

Ok I put on a new EGR Valve and new EVP sensor. Still the problem prosists and after reseting the computer I am still getting code 33. Would replacing the EGR Solenoid Vacuum be the next best bet? Other then that I am completely lost.