Rough idle at standstill

Hey guys! It's been a while since I've posted largely due to me just getting the car back after a 6 month spa(shop) treatment getting some welding and wires re-run for power windows and such.

Since I picked it up, I notice it feels like a rough idle. It sounds choppy for lack of a better word. But when I accelerate, it is still choppy for a few seconds then hums like normal. I have checked the vacuum lines and everything is new and good to go. I'm thinking it is the timing since it hasn't been timed since I've had it. Picked up a timing gun, but I'm not sure how to do it completely. Any suggestions? Also after driving it for 12 miles home, the oil dummy light started flickering lightly then went away. I'm sure that's a contact issue which is no biggie. Thanks in advance for any advice!

I personally like the rough idle sound hahaha With the cam I have in there I have to double peddle it at red lights most of the time. BUt I'm sure yours is not supposed to do that. Someone will chime in to help you out for sure.

If it sat for 6 months it could be the wires have gone bad and/or when they were donig their work they bumped one a little lose.

Put a vacuum gauage on it. Do a search on how to read it. Best diagnosis tool dollar for dollar.

Checking the timing is easy. Disconnect the vacuum line from the distributor and plug it.

Start the car, let it warm up to idle speed.

Shoot the gun at the timing mark. (after connecting it properly, which should be done before you start it)

You will see what the timing is at idle. This assumes the harmonic balance is accurate (usually is but the can slip after a number of years)

I would start it up in a really dark place and look to see if I could see any sparks jumping wires.

I personally like the rough idle sound hahaha With the cam I have in there I have to double peddle it at red lights most of the time. BUt I'm sure yours is not supposed to do that. Someone will chime in to help you out for sure.

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My old engine would idle quiet and smooth. Since I installed the new

Cleveland from Don, with a cam, feels and sounds great

When you hold the Hurst shifter you can feel the power. Love it.

mike

If it sat for 6 months it could be the wires have gone bad and/or when they were donig their work they bumped one a little lose.

Put a vacuum gauage on it. Do a search on how to read it. Best diagnosis tool dollar for dollar.

Checking the timing is easy. Disconnect the vacuum line from the distributor and plug it.

Start the car, let it warm up to idle speed.

Shoot the gun at the timing mark. (after connecting it properly, which should be done before you start it)

You will see what the timing is at idle. This assumes the harmonic balance is accurate (usually is but the can slip after a number of years)

I would start it up in a really dark place and look to see if I could see any sparks jumping wires.

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A vacuum gauge is a 'must have' tool and get one you can also pump down. It is sometimes useful to be able to apply a vacuum.

Good idea about starting the engine in a dark place to look for arcing.

mike

My guess is the carb has trash/build up in it some where

Is it the same fuel as was in there 6 months ago???? Get some fresh fuel in there, I stored mine a couple of years ago with 1/2 tank of gas, it ran terrible!

My guess is the carb has trash/build up in it some where

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+1

Is it the same fuel as was in there 6 months ago???? Get some fresh fuel in there, I stored mine a couple of years ago with 1/2 tank of gas, it ran terrible!

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+2

I vote for trash in the Carb,

i would first flush the tank and refill with new gasoline.

next could be trash in the carb.

I would check timing just to make sure.

but also i would check your idle rpms. spec is between 650-750 on a stock motor.

if your idle rpms are a bit low it will make a rough idle and turn the oil light on and off flickering it.

would not hurt to just make sure your oil level is correct as well.

I would get new gas first. drain the old gas or try to drive it all out of the tank if possible.

after replacing the gas see if things improve.

if not i would check idle rpms, and timing.

last would be remove the carb and rebuild it/clean it out.

if you have a fuel filter i would replace it or change the cartridge if it is a serviceable one.

trash in the carb, did it to me when the mustang was sitting in the body shop.

A vacuum leak will also cause a rough idle. I had a vacuum leak kick my butt all last summer. I finally found it when removing vacuum lines when I started to pull the intake. It had an open port in the vacuum tree on the back of the engine.

I recently dumped a bottle of Redline S-1 complete system cleaner in a full tank...that helped me a lot.

I had my carb tuned and timing set...but was still rough idle and felt a bit sluggish...not anymore

A vacuum leak will also cause a rough idle. I had a vacuum leak kick my butt all last summer. I finally found it when removing vacuum lines when I started to pull the intake. It had an open port in the vacuum tree on the back of the engine.

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I have the same issue, so if you figure it out let me know please

You had it in a shop and you are not happy. You paid the guy? Tell him to fix it until you are happy. These F'g shops gotta get their act together.

I have the same issue, so if you figure it out let me know please

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I think you are experiencing a miss on cylinder #2,4,6 and 8...and maybe also 3, 5 and 7. #1 sounds pretty good though.

I have the same issue, so if you figure it out let me know please

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Mine idles nice and smooth... I'll trade ya!

I have the same issue, so if you figure it out let me know please

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I think the only cure for that condition is a cam change

I recommend the following in this order but really any order should do fine:

a). Ensure the idle RPM to 750-800 (or whatever you prefer) but it should be around 575-600 in drive with the brake pushed in and the lights on

b). Check all of those plug wires and possibly spark plugs. I'd use a timing light on each wire to see if it's getting spark

c). Double-check for vac leaks. Leak might be caused by intake manifold (not likely) as was the case with BOTH my 70 & 72. They were leaking oil though as well in the back.

d). Set ignition timing to 6-12 BTDC. When you rotate the dizzy clockwise the timing will increase.

Vac Gauge and timing light are must haves. I've probably used mine 50 times.

I don't doubt it could be the carb, but my best guess would be spark somewhere. Not that it will fix what I'm hearing in the video, just for the heck of it I'd replace the fuel filter and PCV if they are fairly old.

I had a similar issue, check for any vacuum leaks on carb , lines and pcv , also look for leaking and sloppy hardened valve cover gaskets , etc

Check for old fuel , clogged filters , clogged carb , and check the power valve inside the carb (if it sat awhile with the gasohol / crapohol maybe some carb seals started to decompose)