Diagnosis of Engine Noise/Performance

[EarlD]

1995 Park Avenue 3.8 with 250,000 miles. Running great on interstate at 75mph and cuts off. Pull off to side of road and attempt to start. Very rough crank and will not start. Try again and starts but runs extremely rough with entire vehicle shaking and shuttering. Turn off and wait. Restart with same results but less violent shaking. With each repeat the engine starts with less and less shaking. Engine reaches a point were it starts and runs smooth but has no power when put into D.

Tow vehicle home. Start next day and cranks immediately and runs smoothly. Drive down road about 1/10th mile and back. Turn off. As engine comes to stop there is a 2 knocks with metal grinding sound, very briefly, before engine comes to shut-down.

Engine continues to start immediately, run rather smoothly, but on shut-down the same 2 to 3 knocks with grinding sound. I have not driven the car after the initial 2/10s mile drive for fear of major damage to the engine.

The sound is difficult to locate but seems to be coming from the left rear, upper part of the engine when sitting in the driver's seat.

Anyone have any ideas as to what could be going on? Any help would be appreciated.

 

[Dougie]

May be helpful to drain the oil and see if anything like metal flecks show up, indicating a metal-on-metal wear. My 2002 Lesabre had the exact same condition, running extremely rough and whole car shaking business at start-up. I shut it off and turned it back on and it never did it again and that was a year ago. I also had a 1960 Ford do the same thing. Same thing, I shut it off and started it back up and it never did it again. I wonder if crankshaft position sensor could cause this.

 

[LARRY70GS]

Have a look at the harmonic balancer. If it starts to come apart, it will effect the crank sensor, and will also make a knocking noise. Look at it while the engine is running, you may be able to see it wobbling. It has an inner and outer section separated by a rubber ring. Not all that uncommon on a high mileage engine. A bad balancer fits your symptoms. Hope that helps.

 

[EarlD]

Thanks for the input. All makes sense. Thanks, again.

 

[EarlD]

Larry70GS was spot on. Took awhile to get to the car but when I did pull the front wheel off, it was obvious the harmonic balance had a problem. All the way around the balance, the rubber had separated from the outer metal pulley. It was not easy getting the balance off but once replaced the engine fired right up and I immediately took the car on a 400+ mile trip with not problem. The 24mm bolt which holds the balance on is very difficult to remove. I found videos which showed how to use a breaker bar and a crank of the engine to remove the bolt.

I took all spark plug wires off the coils to prevent the engine from starting when I cranked to loosen the bolt.

 

[Drakito]

You can also pull the fuel pump fuse to keep it from starting hen using the bump start method. Glad you got it worked out.

 

[Zeroboostbuick]

I have 4 different impact guns (all 1/2 drive) and only 1 of them is able to remove bolts that are almost impossible with a breaker bar. Paid $ 60 some 20 years ago and even my $ 300+ impact gun that's rated for 760 ft / lbs is not as strong.

Best way to take off a very tough bolt, is to heat it up with a torch ! works every time like a charm.