Miata Mailing List: May 1996, Message #3
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   From: LSAPEX@aol.com
Subject: Re: Exhaust Pop - Rich Mixture
   Date: Wed, 1 May 1996 15:56:45 -0400

In a message dated 96-04-29 23:09:44 EDT, you write:

>> Has anyone experienced a problem with exhaust popping due to unburnt fuel
>> combusting in the exhaust manifold or header.
>> 
>> -  I have check the oxy sensor an it is performing within spec
>> -  I have checked the header and exhaust system for leaks
>> -  I have has the exhaust gas tested and I am getting reading that
>>    indicates there are significantly elevated fuel levels at the
>>    tail pipe
>> -  No ECU error codes on self diagnosis
>
>I have the same symptoms / 'problem'.  There is a switch on the throttle
>linkage that 
>is supposed to cut the fuel when you lift the throttle.  About two months
ago
>I 
>changed the plugs and examined this switch.  The backfiring was completely
>gone for 
>about a week then came back.  At first I thought it was the plugs, but now
>I'm not so 
>sure.
>
>My car also has high mileage (118K miles) and it could be that the injectors
>aren't 
>doing their job as well as they used to.
>
>I'd like to hear what others think about this.

A free flow exhaust, or very old muffler (with no baffles left) will do this.
I have headers and Borla exhaust, it does it. I think it's cool.

Les.