Backfire at idle

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Aug 30, 2006 | 09:44 AM

01BoostedZ

Thread Starter

Burning Brakes

Joined: Dec 2001

Posts: 921

Likes: 1

From: Albany WI

Backfire at idle

Anyone have any suggestions of where to look for a slight backfire at idle? It just started today. Just a periodic pop that for the most part isn't real loud. It also backfired a couple of times during a slow acceleration. It doesn't backfire at higher RPM's, which is just the opposite of what I would think. I can't feel a miss under acceleration and it doesn't throw any codes. It has always had a little surge in first at low RPMs, if that is somehow related. I know it could be a lot of things. Any help would be appreciated.

Thanks.

Al

Aug 30, 2006 | 10:06 AM

01BoostedZ

Thread Starter

Burning Brakes

Joined: Dec 2001

Posts: 921

Likes: 1

From: Albany WI

I couple of things that I forgot to mention. It's a 99 with 25,000 miles and the backfire is through the exhaust, not the manifold.

Aug 30, 2006 | 10:11 AM

Silver98

Burning Brakes

Joined: Nov 2004

Posts: 993

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From: PA

Take a look at your exhaust system. There maybe a small leak through either a pin hole or a loose flange connection. Its a free check

Aug 30, 2006 | 01:25 PM

dbirdz06

Le Mans Master

Joined: May 2004

Posts: 5,683

Likes: 1

From: Houston Texas

Do you just hear it, or do you also feel it? The reason I ask is because I've been feeling a slight pop/backfire/thud type problem through the clutch pedal and shifter when idling. May be completely unrelated but I'm interested as well.

Maybe it's nothing and I'm just paranoid.
Good luck on the diagnosis.

Aug 30, 2006 | 03:49 PM

01BoostedZ

Thread Starter

Burning Brakes

Joined: Dec 2001

Posts: 921

Likes: 1

From: Albany WI

dbirdz06, I don't feel anything when it backfires. Most of the time it's not a real loud pop. I stood behing the car and it seemed to only be on the left side. I did fill up with some gas after I noticed the backfire and then drove the car for about an hour. I didn't have much time to let it idle afterwards, but I didn't hear any backfiring in the short time it was idling. Might of just been bad gas.

Aug 30, 2006 | 04:05 PM

SpeedyZ

Drifting

Joined: Oct 2004

Posts: 1,384

Likes: 8

From: Southwest Virginia

Sounds like you may be describing a misfire. I would take a look at the plugs. Make sure the plug wires are on good and not damaged. If you can get it to do it regularly you can pull a plug wire or injector wire and narrow it down to a single cylinder. Or if you have access to a OBDII scanner it should tell you which cylinder to look at.

Aug 30, 2006 | 05:47 PM

LoneStarFRC

Team Owner

Joined: May 2001

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From: Dear Karma, I have a list of people you missed.

St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16

Quote:

Originally Posted by SpeedyZ

Good tip. I would also recommend checking your fuel pressure as a good starting point too, both at idle and at a slightly higher rpm. It should stay fairly consistent in the 55-61lb range. It's also possible you may have a hinky injector or two on the left bank.
HTH,
Robert

Aug 30, 2006 | 09:58 PM

01BoostedZ

Thread Starter

Burning Brakes

Joined: Dec 2001

Posts: 921

Likes: 1

From: Albany WI

Thanks for all of the suggestions. The backfire is still there and it seems to have progressed into a slight miss as well. I now notice a slight hesitation after each upshift and some surging at low RPM's when I decelerate. It will probably be this weekend before I get a chance to thoroughly check this out.

Thanks again.
Al