The Ford Barn

AAzz44 · 06-18-2022, 03:29 PM

I cannot for the life of me figure out what’s going on with my 30 A. Car will start fine, however it is super rough idling (like vibrates the entire car pretty good) and has smoke (looks blueish) coming out of tailpipe. I also noticed smoke around the manifold area, possibly near connection with exhaust/muffler.

The manifold was recently replaced due to a crack in it. All shaved off and leveled by machinist.

Any ideas what would cause this rough idle and smoke?

Could be an oiled pump issue?

What’s weird is the car ran fine for hours.

Any thoughts would be appreciated.

Thanks,
MIke A

Jim Brierley · 06-18-2022, 04:05 PM

Could be one cylinder is not firing, may be an oil fouled spark plug?

Chuck Sea/Tac · 06-18-2022, 04:58 PM

Short the plugs one by one to see which cylinder (s) aren’t working. Take a compression test.

Sunny the Model A · 06-18-2022, 06:59 PM

could be running on the rich side maybe? definitely take a comp test if you can and also check each plug, gap em and clean em and see if anything changes. make sure all the jets are flowing right. my truck did something similar slight grey smoke and rough idle. jets were not flowing right.

nkaminar · 06-18-2022, 07:30 PM

Blue smoke is oil burning. Are you getting an exhaust leak noise?

Look at the plugs. The center insulator should be light tan. If black with oil that cylinder is burning oil for some reason.

Do the spark plug shorting trick as others have suggested to find which cylinder is the problem. Do the compression check.

Patrick L. · 06-19-2022, 04:36 PM

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All the above.

Have you tried adjusting the idle mixture since the manifold change ?

Fhane · 06-19-2022, 04:51 PM

Just because a machine shop machined the manifold doesn’t mean it was done right or installed right. It shouldn’t leak. There is a slight chance blue smoke coming from the manifold connection or tall pipe could be residue from machining. Running rough could be a leaking gasket causing low vacuum. Maybe a combination of the two.

Sunny the Model A · 06-19-2022, 07:07 PM

I agree with fhane it could be that. I smoothed and flattened my manifolds by hand with a sander, a straightedge, a file and a whole lot of blasphemy hahaha. Btw fhane, beautiful truck!

old ugly · 06-20-2022, 09:36 PM

white smoke or blue smoke or black smoke?

06-18-2022, 03:29 PM	#1
AAzz44 Junior Member Join Date: Jun 2020 Location: Houston, TX Posts: 28	Rough Idle / Smoke out of tailpipe I cannot for the life of me figure out what’s going on with my 30 A. Car will start fine, however it is super rough idling (like vibrates the entire car pretty good) and has smoke (looks blueish) coming out of tailpipe. I also noticed smoke around the manifold area, possibly near connection with exhaust/muffler. The manifold was recently replaced due to a crack in it. All shaved off and leveled by machinist. Any ideas what would cause this rough idle and smoke? Could be an oiled pump issue? What’s weird is the car ran fine for hours. Any thoughts would be appreciated. Thanks, MIke A

06-18-2022, 04:05 PM	#2
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,088	Re: Rough Idle / Smoke out of tailpipe Could be one cylinder is not firing, may be an oil fouled spark plug?

06-18-2022, 04:58 PM	#3
Chuck Sea/Tac Senior Member Join Date: May 2010 Location: Between Seattle & Tacoma Posts: 2,354	Re: Rough Idle / Smoke out of tailpipe Short the plugs one by one to see which cylinder (s) aren’t working. Take a compression test.

06-18-2022, 06:59 PM	#4
Sunny the Model A Senior Member Join Date: Jul 2021 Location: Charleston SC Posts: 169	Re: Rough Idle / Smoke out of tailpipe could be running on the rich side maybe? definitely take a comp test if you can and also check each plug, gap em and clean em and see if anything changes. make sure all the jets are flowing right. my truck did something similar slight grey smoke and rough idle. jets were not flowing right. __________________ "Quality means doing it right when no one is looking" Henry Ford

06-18-2022, 07:30 PM	#5
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,897	Re: Rough Idle / Smoke out of tailpipe Blue smoke is oil burning. Are you getting an exhaust leak noise? Look at the plugs. The center insulator should be light tan. If black with oil that cylinder is burning oil for some reason. Do the spark plug shorting trick as others have suggested to find which cylinder is the problem. Do the compression check. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

06-19-2022, 04:36 PM	#6
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Rough Idle / Smoke out of tailpipe Sponsored Links (Register now to hide all advertisements) All the above. Have you tried adjusting the idle mixture since the manifold change ?

06-19-2022, 04:51 PM	#7
Fhane Senior Member Join Date: May 2010 Location: Stuart Florida Posts: 148	Re: Rough Idle / Smoke out of tailpipe Just because a machine shop machined the manifold doesn’t mean it was done right or installed right. It shouldn’t leak. There is a slight chance blue smoke coming from the manifold connection or tall pipe could be residue from machining. Running rough could be a leaking gasket causing low vacuum. Maybe a combination of the two.

06-19-2022, 07:07 PM	#8
Sunny the Model A Senior Member Join Date: Jul 2021 Location: Charleston SC Posts: 169	Re: Rough Idle / Smoke out of tailpipe I agree with fhane it could be that. I smoothed and flattened my manifolds by hand with a sander, a straightedge, a file and a whole lot of blasphemy hahaha. Btw fhane, beautiful truck! __________________ "Quality means doing it right when no one is looking" Henry Ford

06-20-2022, 09:36 PM	#9
old ugly Senior Member Join Date: Aug 2021 Location: alberta canada Posts: 585	Re: Rough Idle / Smoke out of tailpipe white smoke or blue smoke or black smoke? __________________ old ugly my old father-in-law told me. "listen close when people tell you how to do stuff they may know something. then do it the way you want."