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General Category => General Discussion => Topic started by: ritratto on March 18, 2015, 11:24:18 AM

Title: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: ritratto on March 18, 2015, 11:24:18 AM

Hey everyone.... My '03 Lemans just recently started backfiring when I throttle down. Whether high or low rev, seems to make no difference, except how loud it is. If I pull in the clutch, it stops, but would feel better if it stayed under power instead of free-wheeling.

What happened and can it be fixed?

Stock exhaust system... nothing fancy going on here. Help!

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: Vasco DG on March 18, 2015, 11:34:04 AM

Air leak in the exhaust somewhere. Does it have a front crossover that loops down under the alternator cover? Is this loose?

Pete

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: rocker59 on March 18, 2015, 11:39:43 AM

I'd check the front crossover for leaky gaskets at the joints with the headpipes.

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: jomarti3 on March 18, 2015, 11:50:17 AM

We had a crack in the front crossover area on a 2004 LeMans.  Fixed, happened again.

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: rocker59 on March 18, 2015, 11:56:52 AM

Quote from: jomarti3 on March 18, 2015, 11:50:17 AM

We had a crack in the front crossover area on a 2004 LeMans.  Fixed, happened again.

Best thing to do for that problem on the '03/'04 Sport/LeMans is replace the headers that delete the front crossover.

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: ritratto on March 18, 2015, 12:19:59 PM

I got some billit aluminum gaskets for the crossover pipe from MPH and fitted them about a year ago and no known leaks there any longer. Crossover is tight. Is there another culprit?

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: rocker59 on March 18, 2015, 12:26:48 PM

Quote from: ritratto on March 18, 2015, 12:19:59 PM

I got some billit aluminum gaskets for the crossover pipe from MPH and fitted them about a year ago and no known leaks there any longer. Crossover is tight. Is there another culprit?

Check the exhaust gasket at the head, and make sure the nuts are tight on the retaining collars.

Otherwise, I'd be looking for cracks in the system.

 

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: Vasco DG on March 18, 2015, 01:05:36 PM

Yup, air leaks are the commonest cause. Check every joint in the system and then go hunting for cracks.

Pete

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: ritratto on March 18, 2015, 01:12:35 PM

Thanks guys... will have another look over it all tonight!

Title: Re: All you V11 Sport/Lemans guys.... Why the backfiring?
Post by: pauldaytona on March 18, 2015, 05:05:02 PM

That "billit aluminum gaskets for the crossover pipe" make that it is tight, but also inflexible, and since the heads dance their shaking dance, chance is that there comes a crack in the stainless pipes. Now or later

Title: Re:
Post by: Unkept on March 18, 2015, 06:42:48 PM

Intakes rubber cracked or loose?