Fyi-rough idle diy
Thread Starter
grumpy old bastard
Joined: May 2012
Posts: 51
Likes: 2
From: louisville, ky
Fyi-rough idle diy
Hey guys
I havent seen anywhere the mention of one of the biggest causes of a rough idle. Granted, this wont be the cure for 100% of all rough idle issues, but it will apply to a large percentage of them.
Especially on older trucks, check the emission hoses that run up to the intake. I'm gonna use my 2003 4.6 as an example, just because its easiest for me.
On mine, the hose that comes off of the center of the passenger valve cover runs from the pcv valve and curls around the back side of the intake, where it goes into the plenum, just behind the throttle body.
The hose has a rubber elbow that connects the tube to the plenum. This elbow deteriorates and can suck closed and eventually wear a hole, or just split and cause a monster vacuum leak. These emission hoses cost guys a lot of time and money.
The most common complaint i hear is the truck will run fine for awhile and then the idle goes goofy. But, it may cause an issue all of the time. These hoses/tubes/elbows are the first thing i look at when it comes to a rough running condition.
On a side note, after doing a test drive and verifying the issue is taken care of, i scan it again to be sure the codes are cleared. At this point i like to disconnect the negative battery cable for a minute and then reconnect it. This will reset the fuel trim tables in the computer. Understand, they will eventually relearn anyway, this is just a shortcut. I then will drive again (just a couple of miles) so those fuel trim tables have a good baseline.
Hope this helps.
I havent seen anywhere the mention of one of the biggest causes of a rough idle. Granted, this wont be the cure for 100% of all rough idle issues, but it will apply to a large percentage of them.
Especially on older trucks, check the emission hoses that run up to the intake. I'm gonna use my 2003 4.6 as an example, just because its easiest for me.
On mine, the hose that comes off of the center of the passenger valve cover runs from the pcv valve and curls around the back side of the intake, where it goes into the plenum, just behind the throttle body.
The hose has a rubber elbow that connects the tube to the plenum. This elbow deteriorates and can suck closed and eventually wear a hole, or just split and cause a monster vacuum leak. These emission hoses cost guys a lot of time and money.
The most common complaint i hear is the truck will run fine for awhile and then the idle goes goofy. But, it may cause an issue all of the time. These hoses/tubes/elbows are the first thing i look at when it comes to a rough running condition.
On a side note, after doing a test drive and verifying the issue is taken care of, i scan it again to be sure the codes are cleared. At this point i like to disconnect the negative battery cable for a minute and then reconnect it. This will reset the fuel trim tables in the computer. Understand, they will eventually relearn anyway, this is just a shortcut. I then will drive again (just a couple of miles) so those fuel trim tables have a good baseline.
Hope this helps.
Junior Member
Joined: Dec 2012
Posts: 3
Likes: 0
that is so true took me forever to find that one but its the first thing i look for n
[QUOTE=beknd4pees;2167715]Hey guys oops put my quate in title but you get the pic
I havent seen anywhere the mention of one of the biggest causes of a rough idle. Granted, this wont be the cure for 100% of all rough idle issues, but it will apply to a large percentage of them.
Especially on older trucks, check the emission hoses that run up to the tintake. I'm gonna use my 2003 4.6 as an example, just because its easiest for me.
On mine, the hose that comes off of the center of the passenger valve cover runs from the pcv valve and curls around the back side of the intake, where it goes into the plenum, just behind the throttle body.
The hose has a rubber elbow that connects the tube to the plenum. This elbow deteriorates and can suck closed and eventually wear a hole, or just split and cause a monster vacuum leak. These emission hoses cost guys a lot of time and money.
The most common complaint i hear is the truck will run fine for awhile and then the idle goes goofy. But, it may cause an issue all of the time. These hoses/tubes/elbows are the first thing i look at when it comes to a rough running condition.
On a side note, after doing a test drive and verifying the issue is taken care of, i scan it again to be sure the codes are cleared. At this point i like to disconnect the negative battery cable for a minute and then reconnect it. This will reset the fuel trim tables in the computer. Understand, they will eventually relearn anyway, this is just a shortcut. I then will drive again (just a couple of miles) so those fuel trim tables have a good baseline.
Hope this helps it helped me thanks
I havent seen anywhere the mention of one of the biggest causes of a rough idle. Granted, this wont be the cure for 100% of all rough idle issues, but it will apply to a large percentage of them.
Especially on older trucks, check the emission hoses that run up to the tintake. I'm gonna use my 2003 4.6 as an example, just because its easiest for me.
On mine, the hose that comes off of the center of the passenger valve cover runs from the pcv valve and curls around the back side of the intake, where it goes into the plenum, just behind the throttle body.
The hose has a rubber elbow that connects the tube to the plenum. This elbow deteriorates and can suck closed and eventually wear a hole, or just split and cause a monster vacuum leak. These emission hoses cost guys a lot of time and money.
The most common complaint i hear is the truck will run fine for awhile and then the idle goes goofy. But, it may cause an issue all of the time. These hoses/tubes/elbows are the first thing i look at when it comes to a rough running condition.
On a side note, after doing a test drive and verifying the issue is taken care of, i scan it again to be sure the codes are cleared. At this point i like to disconnect the negative battery cable for a minute and then reconnect it. This will reset the fuel trim tables in the computer. Understand, they will eventually relearn anyway, this is just a shortcut. I then will drive again (just a couple of miles) so those fuel trim tables have a good baseline.
Hope this helps it helped me thanks