Small throttle abnormality
11-23-2015, 11:48 PM
#1
Member
Thread Starter
Small throttle abnormality
I have a 1996 F150 with the 5.8 and I've noticed that if I try to hold the truck in the range of 1100-1300 rpm, it will rise and fall by 1 or 200 rpm until I either let off or give it more throttle. It happens at low speed when in first or second gear, and it will also happen if I just try to idle the truck at that engine speed in park or neutral. Per my father's advice I sprayed around the vacuum lines with carb cleaner to check for a vacuum leak, and I did not notice any leaks. I also removed the idle air control and cleaned it. The next item on the list my dad told me to look into would be the throttle position sensor. Any thoughts?
11-24-2015, 08:34 AM
#2
1994 F150 XLT 5.8L 2wd
http://www.fullsizebronco.com/forum/...d.php?t=206960
That is a complete walk through on how to properly clean/diagnose the IAC.
This is a walkthrough chris1 wrote up on TPS testing
https://www.f150forum.com/f10/testin...ht=testing+tps
Vacuum lines: Even though spraying carb cleaner or other flammables can pinpoint a major leak, small cracks or poor seals can only be detected by using a vacuum pump/gauge. IMO though it's best to replace the vacuum lines if you have the OEM colored plastic tubing. It takes the same time to replace them all as it does to pull them and test. I replaced mine with 22ft of 4mm line from http://www.siliconeintakes.com/silic...686d47fdf65361. I seriously can't tell you enough how much better these lines are compared to standard rubber lines from the auto parts stores. They are high quality silicone that will outlast your truck. Rubber lines from local store will cost about $0.50/ft and last anywhere from 2-10 years depending on climate and quality of their lines. The silicone lines will outlast the frame/engine on your truck, they aren't susceptible to dry rot or weather checking like regular rubber. With silicone or rubber lines you won't need any boots, just pull the old lines one at a time and slip the new one on, cut to length with a razor, with either one you will need a 4-way vacuum tee (or two 3-ways) to do the TAD and TAB. You also don't need to know what every component does, just replace the lines like you would do plug wires, one at a time and you can't mess it up.
That is a complete walk through on how to properly clean/diagnose the IAC.
This is a walkthrough chris1 wrote up on TPS testing
https://www.f150forum.com/f10/testin...ht=testing+tps
Vacuum lines: Even though spraying carb cleaner or other flammables can pinpoint a major leak, small cracks or poor seals can only be detected by using a vacuum pump/gauge. IMO though it's best to replace the vacuum lines if you have the OEM colored plastic tubing. It takes the same time to replace them all as it does to pull them and test. I replaced mine with 22ft of 4mm line from http://www.siliconeintakes.com/silic...686d47fdf65361. I seriously can't tell you enough how much better these lines are compared to standard rubber lines from the auto parts stores. They are high quality silicone that will outlast your truck. Rubber lines from local store will cost about $0.50/ft and last anywhere from 2-10 years depending on climate and quality of their lines. The silicone lines will outlast the frame/engine on your truck, they aren't susceptible to dry rot or weather checking like regular rubber. With silicone or rubber lines you won't need any boots, just pull the old lines one at a time and slip the new one on, cut to length with a razor, with either one you will need a 4-way vacuum tee (or two 3-ways) to do the TAD and TAB. You also don't need to know what every component does, just replace the lines like you would do plug wires, one at a time and you can't mess it up.
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SoDak Guy (11-24-2015)
