Funny 1991 Volvo sound with foot fully on the accelorator

My sister’s 1991 Volvo 240 automatic. She is scared to drive it.



When we push the accelerator fully down while in park the car makes a sound of accelerating hard and decelerating, it occasionally makes the sound of a backfire. All the sounds are coming from under the hood.



When in drive it will not actually accelerate past first gear, it will buck back and forth, and still makes the sounds. Its almost like a shutter. Reverse is the same.



We recorded the sounds. I will send an email of it for whoever would like to hear it.

If you reply to this post, you should be able to attach the sound file so we can all hear it.

I know you said it sounds sorta like a backfire, but do you know what a backfire sounds like? In advance of the sound file, this sounds like the timing is out of whack, causing the engine to backfire, either through the intake (too early) or exhaust (too late). if the intake, the air hoses and such will muffle it.

Yes. I know what a backfire sounds like (smiling), it does “sorta” sound like a backfire. However here is the sound file so give a listen and see what you think. As I said earlier this sound was created with the accelerator fully pushed to the floor while in park. The same sounds happens while in drive.

Thank you for your quick response.

“When we push the accelerator fully down while in park…”

Hmmm…I wonder how many times this engine has been over-revved.

In any event, the first step is to bring the car up to date with all of its maintenance. If the spark plugs, plug wires, air filter, and fuel filter are overdue for replacement, and/or if the fuel and air intake systems are really gummed up, diagnosing the problem is going to be very time-consuming and perhaps more expensive in the long run.

If you are really lucky, merely bringing it up to date with maintenance will resolve the problem.