Will not idle long or stay running when put in gear

AC1081

MEMBER
1967 MERCURY COUGAR
V8
60,000 MILES

I was driving the car. Everything was running fine then out of the blue, the engine started making different sound like a lower deeper sound and lost power. I was still able to drive it but once I got it home, it's wouldn't stay running. If I idle it high, it will stay running but when I try and put it in gear, it shuts off.

Sunday, June 30th, 2019 AT 11:28 AM

7 Replies

MOTOR MASTER

MECHANIC
279 POSTS

Hello my name is Dave.

As a huge Cougar fan your question caught my attention. My very first thought is timing chain jumped a tooth. If you have all original equipment or equivalent there is not much that can go wrong that would cause the symptoms you have described. What I would do is take the distributor cap off and turn the engine until the rotor button is pointing to number one on the cap then look at the harmonic balancer and see if it's pointed to around 8 degrees BTC, The other thing I would check is how much play is in the timing chain, while you have the cap off turn the crank in one direction until the rotor button starts to turn then turn the crank I the opposite direction and see how far you have to turn the crank before the button starts to move, it should only be a degree or so. If it moves more the timing chain needs replaced. I would also check (personally just go ahead and replace) the fuel filter as you could have picked up some debris and clogged the filter. The other thing that could cause these type of symptoms would be the carburetor. You didn't mention which engine you have, and more importantly which carburetor you have. Regardless of which one if it is a carburetor there is a chance it's a stuck float, try tapping on the carburetor with the handle of a screwdriver while it is running to free it up. I hope this helps you track down the issue and thank you for using 2CarPros.

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Monday, July 1st, 2019 AT 4:47 AM

AC1081

MEMBER
4 POSTS

Hey Dave, thank you for the reply. I will try your idea with the timing. I'm sorry that I didn't include more information. The motor is a 351w with a four barrel Demon carburetor. I have replaced the vacuum lines and fuel filter. Rebuilt the carburetor and tested the fuel pump. I also replaced the spark plugs and wires. There was one wire that had melted into the exhaust manifold but replacing those and the plugs didn't help. Thank you for your time.

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Monday, July 1st, 2019 AT 8:15 PM

KEN L

MASTER CERTIFIED MECHANIC
51,808 POSTS

It sounds like you have a muffler that has fallen apart internally. Can you please shoot a quick video with your phone so we can hear the noise? That would be great. You can upload it here with your response.

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Thursday, July 4th, 2019 AT 4:09 PM

AC1081

MEMBER
4 POSTS

I dropped both mufflers to see if that would do it. Probably not the greatest idea but what's done is done. I ran it until the engine reached operating temperature but it's still doing the same thing. Can you tell me anything by the sounds you hear? I'm running out of options here. Thank you all for your time and patience.

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Friday, July 5th, 2019 AT 6:22 PM

KEN L

MASTER CERTIFIED MECHANIC
51,808 POSTS

Thanks for the video. it sounds like the engine timing chain has jumped a tooth. this will be difficult to check unless you remove the timing cover. sometimes you can tell if you put the engine on TDC and see if the rotor is pointing off slightly. Also a compression test can help as well. Do two cylinders and let me know.

https://www.2carpros.com/articles/how-to-test-engine-compression

Please run down this guide and report back.

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Sunday, July 7th, 2019 AT 12:59 PM

AC1081

MEMBER
4 POSTS

I found the problem. Did a compression test. In the picture are #1, #2 and #4 spark plugs.
#1 pressure was 105.
#2 had none whatsoever. Even after pouring a teaspoon of oil in it.
#4 had 125 lbs of pressure.
So. Burnt valve. Time to rebuild it.
Thank you both for your time, Ken and Dave.

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