Exhaust burbling when you come off accelrator.

[cps13]

Hi,

I have a hyundai coupe 1.6 (2002) which has recently started popping/burbling (and not the good kind) when you take your foot off the throttle.

Any ideas what may cause this?

Plugs are about 2.5 years old. I cannot see any cracks in the manifold, EML came on recently and it suggested sensor in exhaust manifold. Cleared the code and has not come back on since.

Recently had its MoT and got the following on fast idle test...

1st:

CO: < 0.30% vol 0.39 FAIL
HC: < 200ppm 13 PASS
Lambda: 0.970 to 1.030 1.020 PASS

2nd:

CO: 0.25
HC: 8
Lambda: 1.018


Any suggestions welcome. Cheers

[Steve_D]

Sounds like an air leak in the exhaust.
Where you would normally think about an exhaust blow with the gasses escaping, on overrun air can be drawn into the blow and provide oxygen to the hot gasses which then explode in the pipe.

Steve