high idle problem

[sixbanger]

I got the overheating problem (half) solved, the heat riser was stuck and the fan shroud was put back on. Still runs hot but is about 10 degrees cooler now. My next problem on the agenda is the idle. The idle speed screw is turned down all the way but it still idles high and slowly creeps higher and higher, but when its driving or when the brake is on at a stop light is idles at the right speed. What is going on and how can it be fixed?

[Niel Hoback]

It may be that your throttle plate is not closing enough at idle. A vaccuum leak will cause a high idle speed also. Check the fast idle cam on the throttle shaft to make sure its not staying up. Back out the idle adjustment screw and look down the throat to make sure its closing all the way with screw backed out. Check the carb mount screws and manifold nuts. Check the wiper hose for breaks.

[55 Fargo]

Check your throttle linkage, and make sure nothing sticks binds etc.

I had a similar problem, and the pivot point, where the gas pedal linkage is mounted to the firewall, make sure this is clean, and moving freely, that can be a sticking point, and it don't take much to keep the idle up.

Okay so you engine temp problem, is being addressed heat riser, is now working, or just moved to allow exhaust gas to exit freely?

Did you test your temp gauge with some temperature reading device, to verify, and confirm what temp your engine is running at?

I asked you yesterday, does this engine cool down a bit on the highway, as opposed to city driving?

You state the engine is running hot, if it is running 180-190, and it is still 65 outside, that ain't too bad. Are you running a t/stat, and if so, what degree, 160,180 or none?

I don't know where you are located, but if your March temps are 60s, then you are in an area that has long hot summers, you will want to address the engine heating problem, before those 90 degree days of summer..... BTW nice survivor car you have there

[sixbanger]

The temp guage is brand new, I am running no thermostat although I've read on the forum that its better to have one than none. I have not been able to drive on the highway as the car is not legal yet but I've been doing some driving on side streets in town. 20-30 MPH max, when I get some speed the temp does go down some. The throttle return spring broke in two and got replaced with a stronger one. When the gas pedal is pushed down the linkage works fine but I noticed that when it returns it goes fast at first but then stops and slowly goes all the way back down.

Edited March 13, 2011 by sixbanger

[Andydodge]

A thermostat is in the system for 2 reasons....ONE, to restrict the coolant at start up so that the coolant gets hot and gets the engine to a working temperature and TWO.....it then opens at the predetermined temperature setting, ie, 160 or 180 degrees and lets water flow thru the system BUT due to its restrictive design it allows the coolant to stay in the radiator sufficently long enough to COOL.........with no thermostat the coolant just gets pumped thru the engine and radiator too quick and doesn't spend enough time to cool...........am not doubting your other problems but stick a thermostat in...........they do actually work.........andyd

[Dodgeb4ya]

I got the overheating problem (half) solved, the heat riser was stuck and the fan shroud was put back on. Still runs hot but is about 10 degrees cooler now. My next problem on the agenda is the idle. The idle speed screw is turned down all the way but it still idles high and slowly creeps higher and higher, but when its driving or when the brake is on at a stop light is idles at the right speed. What is going on and how can it be fixed?

It's your carburater. The Stromberg carbs have a throttle side lever plate to throttle shaft wear loosing issue. The throttle shaft to throttle side lever swage gets loose and the throttle plate is not accurately held in position in relation to the throttle shaft- cause of uneven idle control. Not easy to fix!

Bob

[Don Coatney]

Where is your ignition timing set? Too much advance will cause high idle and running hot.

[Dodgeb4ya]

Regardless of timing you should always be able to slow idle speed with idle speed screw.

Bob

[Don Coatney]

Regardless of timing you should always be able to slow idle speed with idle speed screw.

Bob

That is not the case on my engine. If my timing is too far advanced no carburetor adjustments will slow the idle down.

[Dodgeb4ya]

That is not the case on my engine. If my timing is too far advanced no carburetor adjustments will slow the idle down.

I agree to some extent Don, but if the throttle plate is completely closed , no air to the cylinders which means engine cannot idle/run at slow speed. I've dealt with several of these erractic idle dodges over the years with a worn out stromberg carb. A major vacuum leak is one other cause of uncontrollable idle.

Bob

[P-12 Tommy]

Check your throttle linkage, and make sure nothing sticks binds etc.

I had a similar problem, and the pivot point, where the gas pedal linkage is mounted to the firewall, make sure this is clean, and moving freely, that can be a sticking point, and it don't take much to keep the idle up.

Okay so you engine temp problem, is being addressed heat riser, is now working, or just moved to allow exhaust gas to exit freely?

Did you test your temp gauge with some temperature reading device, to verify, and confirm what temp your engine is running at?

I asked you yesterday, does this engine cool down a bit on the highway, as opposed to city driving?

You state the engine is running hot, if it is running 180-190, and it is still 65 outside, that ain't too bad. Are you running a t/stat, and if so, what degree, 160,180 or none?

I don't know where you are located, but if your March temps are 60s, then you are in an area that has long hot summers, you will want to address the engine heating problem, before those 90 degree days of summer..... BTW nice survivor car you have there

I agree with Fred on the throttle linkage part. I myself has an idle problem with the throttle stem grommet being worn out. It was rubbing on the hole in the toe board. Replaced it and no problem.

Tom

Edited March 13, 2011 by P-12 Tommy
Add to it

[Dodgeb4ya]

Yep, I gotta backup and also agree #1 is the throttle linkage out of adjustment or binding as Fred states!

[Phil Martin]

Do you have fluid drive? If my idle is set a little fast it has to be going at higher speed for it to shift.

[Guest P15-D24]

make sure it has 1/16 to 1/8 play in the cable. Without the play the engine movement can cause an intermittent fast idle.

[greg g]

Another simple thing to look at is a weak throttle return spring. In my case it was the high ilde cam that is attached to the chole butterfly, the small spring was gone and the linkage did not retun the cam to the fully off position.

The high idle cam is a piece of tapered sheet metal attached to the throttle shaft upon which the idle speed adjustment screw rides, connected by a piece of linkage to the choke pivot shaft.

Also if manual choke, assure you choke cable is fully opening the choke butterfly.