I guess you reset the computer. Disconnecting the power for 10 minutes reboots the computer. Rebooting works on PC's so why not on car computers

 

Hello all


I had the same problem with my truck (88 F-150 4.9) for 12, yes 12 years (won't idle until its warm, right) The past few months it has been running really really bad and getting worse so I started replacing EGR system sensors and valve, no help . My friend came over and while I kept it running he started un pluging things one at a time. Once he unpluged the MAP sensor it started running like a dream. Went to the parts store bought one for 50 bucks and now it runs better than it ever has since I've owned it and gets about 5 MPG more. I also pulled the memory codes and did a Key On Engine Running test and nothing about the MAP sensor showed up. So, in short, the first thing that I would replace is the MAP sensor.

 

i had a similar problem with my 92 302, it wouldnt hold a steady idle jumping 300rpm back and forth until i started moving. ran the codes and it came up with 02 sensor but thats because i removed my smog pump and other emissions. my problem was the secondary fuel (folgers) can. on of my lines had ripped ank kinked its self causing too much vacuum. replaced vacuum line and she runs like a dream again. SO CHECK YOUR VACUUM LINES!!!! good luck

 

Just a follow up. I went to the auto parts store, and the guy let take the MAP sensor out to the truck and plug it in. It didn't seem to help anything. Then he suggested the idle air control(IAC), but I decided to go home and clean it up. I took it off and sprayed the you know what out of it with carb cleaner, which didn't seem to help either. I unscrewed the motor from the IAC and looked at it while the truck tried to run. I would push the pin in with a screwdriver, and watch the motor to see if it went in and out. I really couldn't tell. I do know that when I unplug one of the caps on the stem going into the throttle body it runs great, but you can't go around with no pressure to the fuel regulator. I also inspected the vacuum line visually. Any ideas.

 

When reading in the haynes manual for the truck, I came acrost the throttle position sensor. The troubleshooting of the device sounded just like the problem I was having, so I replaced it. $25. The truck ran better, but that wasn't it. I took the advice of EPNCSU2006, and began to check the EGR system. The manual says the EGR position sensor should read 5000 ohm's when closed and slowly decrease as vacuum is applied to 100, but no less than 100. Mine read 3030 when closed and 30 when open. Advanced auto had two different ones, so I checked them in the store with the ohm meeter. One had the exact readings as the one I was replacing. The other went from 4010 down to 110, so that's the one I bought, $25. The truck runs alot better, but it still lopes when I first start it, and will die if I don't keep it running, but then runs great. It doesn't sound like it's trying to suck air when I get on it now (EGR). I read somewhere about the gasket between the throttle boddy and intake manifold going bad after 65,000 miles? anyone else got any leads. Thanks for reading this long post!