Rough Idle
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Rough Idle
My 95 f150 4.9 147K Manual and idles at about 1K and is rough. I have tried the standard rough idle procedures with no luck. I have no check engine light and the only thing that is not on par with what I read is my idle is high. I don't know if that is clue enough to suggest a fix but I don't know what else is suspect. Any and all suggestions are welcome and appreciated. If I haven't tried your suggestions prior, I will. Thank you Sandymane
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
It pulled a code 33 which is EGR not opening fully or a few other things. I have never pulled codes on an OBD1 vehicle so I didn't check. Thanks guys for the help and recommendation to check codes. I'll see if the search
suggestions work first without buying a new EGR which is last on the list.
suggestions work first without buying a new EGR which is last on the list.
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Lead Driver
Joined: May 2011
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There are a few things to check in regard to the egr...first, take vac hose off of the egr diaphragm and apply vacuum tester. It should hold vacuum, if it doesnt, the diaphragm is bad and the valve needs to be replaced...if it does hold vacuum, move on (although the valve itself could be stuck from gunk).
Next, check for vacuum leaks in the vac circuit to the egr.
If there are no leaks, and the valve holds vacuum, then you should remove valve to make sure it's not stuck. If it moves freely, test the evp sensor on top of the valve to make sure it's giving proper feedback.
The egr solenoids rarely go bad, if all else test ok then that's the likely culprit.
Next, check for vacuum leaks in the vac circuit to the egr.
If there are no leaks, and the valve holds vacuum, then you should remove valve to make sure it's not stuck. If it moves freely, test the evp sensor on top of the valve to make sure it's giving proper feedback.
The egr solenoids rarely go bad, if all else test ok then that's the likely culprit.
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Fleet Owner
Joined: Oct 2005
Posts: 20,780
Likes: 1,746
From: Kentucky
It pulled a code 33 which is EGR not opening fully or a few other things. I have never pulled codes on an OBD1 vehicle so I didn't check. Thanks guys for the help and recommendation to check codes. I'll see if the search
suggestions work first without buying a new EGR which is last on the list.
suggestions work first without buying a new EGR which is last on the list.
Thread Starter
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Yes I have the 1 1 1 code now. Today I replaced the EGR and the IAC. The truck now runs much better but I still have the high idle but it is not as rough as it was. It is about 1300. I have no vac leaks that I can find and have no idea where to go from here. The only thing that comes to mind is the TPS. From looking at the Chilton manual I don't have a clue how to check it due to the terminology. Does anyone have an idea I can try and how to do it? I will try. Thanks Sandymane
Lead Driver
Joined: Aug 2009
Posts: 7,553
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From: Laquey, MO
Spray some carb cleaner along where the upper and lower intake manifolds join and the around each intake runner where it meets the head. Those are the most likely areas to have a leak. I swore up and down that I didn't, but sure enough there it was.
If that's all good, you IAC valve may have an internal failure that is causing the vacuum leak.
If that's all good, you IAC valve may have an internal failure that is causing the vacuum leak.
Fleet Owner
Joined: Oct 2005
Posts: 20,780
Likes: 1,746
From: Kentucky
If the TPS output was above 1.0 VDC there would have been a code.
Fleet Owner
Joined: Oct 2005
Posts: 20,780
Likes: 1,746
From: Kentucky
If the idle RPM drops or the engine stalls it's most likely something electronic. An out of specification sensor such as the ECT, MAP or ACT can do it. The output may not be far enough out to trigger a code. Could be a computer going bad too. Pull it out then inspect for signs of leaking capacitors. Very common problem with different symptoms from time to time.