Jump to content

Backfire in Olds 307 - '84 Riv


Guest 84riviera

Recommended Posts

Guest 84riviera

Hi all, This has been going on for about 2.5 weeks now. If I give it any more than 1/4 throttle, the engine backfires through the carb and nearly stalls (it has stalled once actually). I hear a ticking sound from the area around the distributor, ticks about every 5 seconds, no pattern to the ticks. Sounds like sparks. I changed the cap and plugs in the fall.

If I'm at a stop but in overdrive (or drive) and give it the amount of throttle I used to give it, it happens. However if i start it in 1st and manually upshift, it doesn't happen as much. Keeping it out of OD does nothing. Timing is set at 20 degrees adv, with ALDL grounded, but still happens.

Trans fluid level is fine, so is oil. I changed trans fluid in the fall.

The only thing I remember doing to the car before this started to happen was I ran 1/2 bottle of Seafoam through the carb. Would this be the problem, or is this a trans issue?

Link to comment
Share on other sites

I'm in the car repair business so I will try to help you. You have spark jumping around at the distributor. The first thing I would suspect is a

burned out ignition rotor with a hole burned through the plastic. Remove the cap and remove the rotor and inspect it for a hole burned through in the plastic

underneath the center spring contact. If you have any doubts about it change it. While the cap is off, make sure the carbon tip protruding from the center

of the inside of the cap is in good shape and not broken or burned off. Also, when you changed the cap did you transfer the ground strap for the ignition coil to the new cap?

I believe one of the things I just mentioned will be the issue. Another possibility if the cap and rotor are OK is that one of your plug wires is bad and the spark is jumping

around inside the cap because it can't find a ground through the open plug wire. Regards, Winston

Link to comment
Share on other sites

Guest 84riviera
I'm in the car repair business so I will try to help you. You have spark jumping around at the distributor. The first thing I would suspect is a

burned out ignition rotor with a hole burned through the plastic.

Thanks Winston, I'll inspect the cap and areas you specified. I'm not sure about the ground strap for the coil though.

Link to comment
Share on other sites

Thanks Winston, I'll inspect the cap and areas you specified. I'm not sure about the ground strap for the coil though.

When you transfer the ignition coil from one cap to another it is easy to not notice the ground strap for the coil which the coil sits on top of. It must

be transfered to the new cap before installing the coil in the new cap. Also check and make sure the spring that pushes on the carbon tip in the middle of the cap that sits under the coil is in good shape.

Link to comment
Share on other sites

I'm in the car repair business so I will try to help you. You have spark jumping around at the distributor. The first thing I would suspect is a

burned out ignition rotor with a hole burned through the plastic. Remove the cap and remove the rotor and inspect it for a hole burned through in the plastic

underneath the center spring contact. If you have any doubts about it change it. While the cap is off, make sure the carbon tip protruding from the center

of the inside of the cap is in good shape and not broken or burned off. Also, when you changed the cap did you transfer the ground strap for the ignition coil to the new cap?

I believe one of the things I just mentioned will be the issue. Another possibility if the cap and rotor are OK is that one of your plug wires is bad and the spark is jumping

around inside the cap because it can't find a ground through the open plug wire. Regards, Winston

This is well informed advice. However, with the spark scattering from cylinder to cylinder, I would also expect some backfiring to be occurring in the exhaust. Perhaps that is happening but you are not noting it or unable to hear it.

Generally, ignition problems will create backfiring in both the intake and exhaust whereas backfiring only in the intake points to carburetion.

Is the sound backfiring or muted "popping"? If it is muted popping it could be an intake valve which occasionally does not seat allowing combustion back into the intake. How does it run otherwise? Does it idle smoothly?

Tom Mooney

Link to comment
Share on other sites

Guest 84riviera

I misted the cap with water and it made a more intense ticking. So I replaced the cap and rotor today, and nothing has changed. Still ticking, still backfiring, still leaving an area of carbon on the inside of air cleaner. I can feel current on the #2&6 wires. What do you folks think is the issue?

Link to comment
Share on other sites

I misted the cap with water and it made a more intense ticking. So I replaced the cap and rotor today, and nothing has changed. Still ticking, still backfiring, still leaving an area of carbon on the inside of air cleaner. I can feel current on the #2&6 wires. What do you folks think is the issue?

I think the next step would be a fresh set of spark plug wires.

Link to comment
Share on other sites

  • 3 weeks later...
Guest 84riviera

Sorry, meant to update this. Yes, it was the wires. I must have been running on 6 or 7 cylinders for a long time! Now its stronger than ever.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...