rough idle

[Anonymous]

Hi guys, I have been having trouble with my '62 falcon 170cid fordomatic. The thing is that it has a rough idle. I had it running up at near 1000rpm and had great help with the falcon forum, so they helped me set it down to the 450-500rpm. I had checked everything with the vacuum gauge and it gives me a reading of 16-17inches but the needle goes up and down quickly(shaky) between these two numbers. According to the gauge it is a late ignition. I have the timing set at 10degrees. I have played with the idle speed and the way it is now is the smoothest I can get it but it's still shaky while idling. I hear the engine run smoother if I screw the idle mixture all the way in and I know that can't stay like that. I thought that maybe I had a carburetor leak so I replaced the gasket and it went up an inch on the gauge but the roughness is still there. While idling the inside generator light flashes on and off. Everything is basically new or rebuilt, the distributor, the voltage regulator, the starter solenoid, the generator, the only thing not rebuilt is the starter. All of the spark plug wires, the coil and points were changed to pertronix. I replaced the distributor cap, have set the spark plug gap between 35-40 but it seems to run best at 40. I took the car out tonight and reducing the rpm really made the car run a lot smoother. By now I am not sure as to what else I should check. I read somewhere that the valve guides might be worn because of the shaky needle on the vacuum gauge, I'm willing to do this but I need to be sure that the problem is there. I would greatly appreciate the help. Thanks to all.

 

[wallaka]

Sounds like the idle is a bit too low...isn't it supposed to be around 650-700 with an auto?

 

[Anonymous]

Hi thanks for responding, According to the manual engine idle rpm with a fordomatic is: 475-525rpm and vacuum should be at 18inches. Thanks.

 

[addo]

The idle's set in gear, motor warm, with the electricals loaded up. That's so if you are at a stop sign on a cold rainy night with the radio playing, it won't stall out. Typically it will go up 100-200 RPM when slipped into N.

It's normal for the GEN light to flicker at slow idle; that's one trait of the generator based charging systems - some people found they are inadequate for driving environments where much time is spent at idle with accessories loading the system.

Regards, Adam.

 

[wallaka]

That's what I was thinking about but didn't fully explain. I don't trust the parking brake and don't usually have somebody to hold the brake for me, so I usually set it by ear. I idle it down until it idles smoothly in Drive and doesn't try to take off. When I check with my dad's dwell meter it always ends up at around 650 rpm.

 

[mkgcars]

I saw similar unsteady vacuum readings on my 170 when the valves were out of adjustment.

I have adjustable rocker arms and hydralic lifters though (I think the lifters are a bit sticky - thats another story) and I was able to reset them so that the vacuum is now a steady 19.

I believe the older ('64 and older? - not quite sure) 170 motors had non-adjustable rocker arms. But you may want to check, if the motor was rebuilt they have changed it over.

matt

 

[Anonymous]

It might be worth the effort to check TDC of the #1 cylinder and compare to the timing mark on the balancer to make sure the ring on the balancer has not slipped.
Doug

 

[Anonymous]

Hi again guys, I was about to check the valves when I checked the tdc mark on the #1 cylinder. I took off the distributor mark and tried to line it up to the number 1, the tdc doesn't line up straight on. I did replace the timing chain about a month ago and before that the distributor. When I replaced the distributor I made sure that they lined up, I had to work on it but got it right. Now if the balancer ring did slip, is there a way to check that? Would I need to rebuild the balancer? Thanks for all the help.

 

[Anonymous]

I would not go on the rotor position as the sole indicator of TDC. You probably should pull the #1 piston and either use a piston stop/ TDC indicator or a long screwdriver or rod. Rotate the engine CW and CCW and note where the piston is at it's highest on the compression stroke. The timing mark indicator on the balancer should line up with the TDC indicator on the timing cover. And the rotor in the distributor should be pointing in the vicinity of the #1 post on the distributor cap. If you have your ignition timing set at 0 degrees, then the rotor should point to the #1 post, but otherwise, it is going to be off slightly.
If the balancer ring is off, then your timing reference is off and when you use the timing light, the timing will not be correct. To correct it you will need a new or rebuilt balancer.
Doug

 

[cfmustang]

I can confirm that this can cause you problems tuning your engine. Mine was off by 10 degrees! As a short-term solution, you can just add a new corrected TDC mark on your balancer with paint (that is what I did), but eventually you will want to replace the balancer. If it has slipped earlier, you can bet it will continue to slip.