Slight exhaust back fire at idle?

1bad914 · 03-19-2012, 06:59 AM

When a sit at a light or a drive thru i am getting a slight backfire thru the exhaust, it is not real loud, but enough to make it sound bad. The rest of the time the car runs great. It is an 84 3.2 with SW chip and a cat bypass. Any ideas?

Porsche Head · Porsche Head's Garage

If the mechanicals are good (compression etc.) then a lean condition or ignition issue.

Cliff

Tippy · 03-19-2012, 07:37 AM

You must have an exhaust leak around the cat bypass.

1bad914 · 03-19-2012, 08:57 AM

I will check it tonight once it cools off. I drove it today, 80 degrees in March...in Michigan!

vancouver86/911 · 03-19-2012, 06:18 PM

How exactly do you check for and locate an exhaust leak?

1bad914 · 03-20-2012, 03:33 AM

Put your gloved hand over the end of the tailpipe and listen for the exhaust escaping out somewhere, not the most accurate, but it works.

db_cooper · db_cooper's Garage

Could be an exhaust leak or it is a classic symptom of leaking intake manifold gaskets..a slight "pop" or "piff" out of the exhaust at idle.

You should check the tightness of the intake manifold to cylinder head nuts and see if they are loose. By the time the engine starts popping at idle..the gaskets have already failed. Re-torque may not fix it.

Not a bad job. It takes a long afternoon. Gives you a chance to inspect and replace your fuel lines too.