ok I have a 1985 camaro sports coupe. first vehicle ever owned. having a couple problems with it. first one is when I drive the car around a bit and go to turn it off, I'll turn off the ignition and the engine will still sound like its trying to turn, sort of putt putting. and it will rattle the car. think it might be a timing problem but not sure.

 

My car does that because it has high compression. Try using mid-grade or premium grade gas. Regular octane burns to hot. This should work. It does for mine.

 

Welcome to TGO.

Sounds like your car is diesling? Could be a timing issue. Being that it's your first car, if you have not already done so, I'd suggest you invest $20 into the purchase of a Haynes or Chilton's repair manual for the year / model. The first two chapters cover maintenance and trouble shooting. You'll find this topic covered there.

Good luck

 

I agree with Wade. your car is probably dieseling. If your car is carbed, check the idle speed and adjust on the carb. If it's not that check your ignition timing.

 

My old car used to do that. turned out to be my ignition was bad, alternator voltage was leaking past the bad switch causing the car to keep running badly, due to high resistance on the line, for a few seconds. Not too hard to check if you cant figure it out.

 

How can timing cause this? When you turn the car off, it shuts of the spark. So timing doesnt come into play.

If it sounds like its trying continue to run( dieseling) that is normally cause by excessive carbon deposits.

 

thanks for the info guys, my dad says he thinks it might be the distributor. just need to get him off the truckin road so he can come down and help me look at it.

 

Run-on for a carbed car is typically caused by too much air/fuel getting into the intake after the engine is shut off. This extra air/fuel combined with a hot, older motor (probably with carbon deposits) will self-ignite, hence the term 'dieseling'.

When the key is off, the dist is not getting power and the spark plugs are not firing. IF they were firing the engine would continue to run normally.

Dieseling is most likely caused by a vacuum leak or a higher than normal curb idle speed. If your engine idles around 600 rpm look for a vacuum leak. Sometimes simply clamping a pair of pliers on each line to crimp it with the motor running will indicate where the leak is. Another option is to plug each vacuum line at the carb or manifold and reconnect one at a time. A vacuum tester (mityvac or brake bleeder) can be 'borrowed' from AZ or one of the others.

 

You wouldn't think timing would have anything to do with this since the ignition system is dead when the key is switched off. But there is a way that it does. As an engine wears the timing chain stretches and the distributor gear wears, this makes the timing later and later. This retarding of the timing slows the idle speed causing stalling. The natural response is to adjust the curb idle speed up. This is a recipe for the engine to diesel when it is shut off.
If the timing is set back up to spec, the high idle speed will become apparent.
So, long story short, wrong timing can cause engine run-on or dieseling.
Other causes include:
PCV valve system stopped up causing over-rich idle which is compensated for by the idle setting being raised.
Engine above stock operating temperature at shutoff.
Rebuilt engine that has been bored, the heads resurfaced, resulting in higher than stock C/R with 87 octane rot-gut (cheapest) gasoline.
EDIT: This is for carb setups not EFI.

 

Good point and something I've never thought of.