Idle Speed Varies
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Elder User
Joined: Dec 2010
Posts: 562
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From: Texas
Idle Speed Varies
I'm making progress working out the bugs on my new 66....the types of things that come with a vehicle that's been stored for many years.
The following has me stumped though:
The idle speed tends to vary while the truck is in nuetral. And, by vary, I mean pretty dramatically. I just went through the carb and I'm fairly certain that I did a good job, but this varying idle thing is frustrating me.
One thing I did notice in the carb was that the "Power Valve" was not moving as freely as I think it should be. Unfortunately, the power valve cannot be repaired as far as I can see. It looks to be an integral part of the top of the carburetor. I don't know if that's relevant to my issue though.
I'll be replacing a bad lifter after work today and adjusting the valves. I can see how that might adversly affect the idle, but causing it to vary like that?.....
Anyone have any ideas?
The following has me stumped though:
The idle speed tends to vary while the truck is in nuetral. And, by vary, I mean pretty dramatically. I just went through the carb and I'm fairly certain that I did a good job, but this varying idle thing is frustrating me.
One thing I did notice in the carb was that the "Power Valve" was not moving as freely as I think it should be. Unfortunately, the power valve cannot be repaired as far as I can see. It looks to be an integral part of the top of the carburetor. I don't know if that's relevant to my issue though.
I'll be replacing a bad lifter after work today and adjusting the valves. I can see how that might adversly affect the idle, but causing it to vary like that?.....
Anyone have any ideas?
Laughing Gas
Joined: Dec 2010
Posts: 1,091
Likes: 14
From: Tucson, Arizona
I would be looking for a vacuum leak or leaks, especially as you say the truck was stored for a number of years and things have a tendency to crack or dry up and shrink. Besides vacuum hoses, check for leaks around the base of the carburetor and the edges of the intake manifold. Good luck.
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Elder User
Joined: Dec 2010
Posts: 562
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From: Texas
Thanks for the reply....
I spent yesterday evening in the garage and seem to have solved the issue.
I replaced the PCV and the associated rubber hose and grommet and noticed that that particular hose's connection to the carb was questionable (so that may have been a vacuum leak).
I also pulled the pushrod cover and valve cover, in anticipation of installing a new lifter, but first I adjusted all of the valves while the engine was running (what a mess) and found that the exhaust valve for #5 was very loose. After adjusting it, the lifter tapping sound went away and the idle smoothed out to almost perfect.
So....my solution was either fixing the PCV hose leak or adjusting the valve properly, or both. Either way, the old truck is running very smoothly this morning.
An added benefit this morning was that during my morning commute through The Woodlands, TX (very upper-class neighborhood), my truck was smoking like a mosquito fogger as it burned off all the spilled oil on the block that I couldn't get to when I cleaned up last night. The looks of horror on the faces of the many BMW and Lexus drivers was well worth the half-dozen burns I got last night while adjusting valves on a hot engine.
I spent yesterday evening in the garage and seem to have solved the issue.
I replaced the PCV and the associated rubber hose and grommet and noticed that that particular hose's connection to the carb was questionable (so that may have been a vacuum leak).
I also pulled the pushrod cover and valve cover, in anticipation of installing a new lifter, but first I adjusted all of the valves while the engine was running (what a mess) and found that the exhaust valve for #5 was very loose. After adjusting it, the lifter tapping sound went away and the idle smoothed out to almost perfect.
So....my solution was either fixing the PCV hose leak or adjusting the valve properly, or both. Either way, the old truck is running very smoothly this morning.
An added benefit this morning was that during my morning commute through The Woodlands, TX (very upper-class neighborhood), my truck was smoking like a mosquito fogger as it burned off all the spilled oil on the block that I couldn't get to when I cleaned up last night. The looks of horror on the faces of the many BMW and Lexus drivers was well worth the half-dozen burns I got last night while adjusting valves on a hot engine.
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Elder User
Joined: Dec 2010
Posts: 562
Likes: 1
From: Texas
yeah....safely and successfully driving a 45 year old vehicle in suburban Houston traffic requires that one drive slowly and carefully. One of the big components to this is keeping good distances between you and the guy in front of you to allow for adequate stopping distance. Also, the common practice of frequent lane-changing is a no-no.
A lot of the folks in the area that I drive through to get to work, drive very nice, good-handling machines, and this tends to instill in them a false sense of confidence in their driving abilities.
So....a guy like me, in an old truck that sticks out like a sore thumb, driving very deliberately and somewhat slower than most of the traffic, really irks a lot of these folks.
I do however, get a lot of smiles and thumbs-ups too.
I just find it amusing, driving something like this through such an affluent, fast-paced area.
