Engine noise during acceleration

[65-coupe]

My car has been running really good. But the other day it started to sound like it was spark knocking. I run 93 octane in it. I checked the timing and it was where it should be at 12. I lowered the timing down to 6 and it still made the noise. It only does it when I accelerate going forward. It will not do it in reverse even at high rpms. If I hold the brake and give it gas it still does not do it. If I go in reverse and then stop quick it will make the nose while braking hard. But does not do it braking going forward. I think maybe something to do with the thrush bearing maybe. What ever it is it seems to only do it when the engine is being pushed back. I did check the torq convertor bolts and they were tight. I have a DUI dist and it is working properly/ vac advance/ mech advance. Any help would be great.

 

[dagenham]

Have you noticed any noise when you are starting the car, like the starter gear is hitting the flexplate when the bendix engages??

 

[65-coupe]

Nope starts normal with no noise. It sounds like a rattle can noise. I don't think it is spark knock anymore because of how it does it when I stop fast while in reverse.

 

[65-coupe]

What about the fly wheel having a crack in it?

 

[bubba22349]

Yes that could and has happened.

 

[65-coupe]

Hopefully I will have time to check the fly wheel on weds. Not sure what else it could be.

 

[bubba22349]

Yes to above part of your post thrust bearing (engine main) though usually not so much in an auto car you can check it with dial indicator in the car easy though, Also if this is a high mileage unit can be a bad torque convertor there are also thrust washers inside the trans.

 

[65-coupe]

Ok would that only make the noise going forward and not reveres? It is also odd how when I stop from going reverse it makes the same noise. The car runs really good and it shifts normal.

 

[bubba22349]

Well a cracked flex plate will be making nose weather it's going forward or backward when ever it has a load on it pretty much the same for a T.Q.

 

[Asa]

Without actually hearing the noise, how are the universal joints?

 

[65-coupe]

They are good. At cruising speed there is no noise only during aceleration or when stopping from reverse.

 

[hutchstang]

Check your rods... hope its not a bent rod

I had the same thing happen to me but just messing around with my vacuum timing and the mixture screw I got the clicking to go away.

good luck

 

[65-coupe]

I will try that, but when I just ran the mech advance it still did it. How do I mess with the vac timing. I have had my DUI for over a year now. It just sems odd for it to happen out of the blue.

 

[Asa]

They are good. At cruising speed there is no noise only during aceleration or when stopping from reverse.

Doesn't necessarily mean anything.

On my truck I had one bad u-joint, cruising would have no sound, but accelerating would cause a helluva racket. The lip that held the seal on had somehow cracked and the needle bearings had slipped out so there was a gap between the center of the u-joint and the cup
When cruising it would press against one edge of the cup, but when accelerating it would rattle back and forth.

 

[65-coupe]

I will check the u-joints out tomorrow. I did jack the rear of the car up and put it in drive with no noise. Gotta love noises that hide themself.

 

[dagenham]

I had a u-joint that was completely shot and could not find it until I took the driveshaft completly out of the car and had it laying on the floor.

 

[65-coupe]

Pulled the drive shaft today and the u joints are good. Pulling the trans tomorrow and check the flywheel and torque converter. Hopefully I will fond it tomorrow. Thanks for all the replies and I will post what I find.

 

[ludwig]

I had a loose flex plate. It made a terrible noise on acceleration right under the hump next to the driver's seat. It started all of a sudden one day. You never said where the noise was coming from and so I stayed out of the discussion. Now it's getting close to a problem I had. The nuts connecting it to the torque converter had come loose and my old-time mechanic diagnosed and corrected the problem with Loc-Tite on the nuts. No problem since.

I hope it is that simple to fix.

 

[65-coupe]

I hope it is to. The bolts were tight so I am going to look at the converter and the plate around the middle. The sound seems to be coming from the back of the engine or the trans. Hope it is a cheap fix with only time being the pain. Car still runs really good even with the noise.

 

[ludwig]

I tightened my bolts to spec but they ended up working loose, not coming off, so the plate fluttered on acceleration. You can check it out through the observation plate first before you drop the tranny. Just rotate the crank in front and check the nuts and/or the plates for looseness and motion while it is still in the car. I think there are only four nuts.