Exhaust is not coming out of pipe as it should, loss of power, truck is quieter than usual and hisses when accelerating. help?

Asked by Mar 01, 2015 at 02:18 AM about the 1994 GMC Sierra 1500 K1500 SL 4WD Extended Cab SB

Question type: Maintenance & Repair

The day before this started , the
truck was misfiring and there was a
small exhaust leak coming from the
manifold at idle. The rpm's surge
while idling like it's not breathing as it
should. When idling the hissing is not
detectable unless one gets down
and listens by the rear tires. So all in
all, something is not letting exhaust
escape where it should if at all. What
could cause this?

3 Answers


Most likely a clogged catalytic converter. But check the rest of the exhaust system for damage such as dented or crushed pipes or muffler. The catalytic converter has a honeycomb type "brick" inside that can become clogged. Since your truck is 21 years old this is a real possibility. If the truck has been misfiring, burning oil, or leaking coolant internally the converter is most definitely clogged. HTH. -Jim

2 out of 2 people think this is helpful.
Best Answer

Perfect. That's exactly what it was. Honeycombs were all broken up and clogged the pipe. Thankyou!

1 out of 1 people think this is helpful.

You're welcome. Glad to help. Thank you for the best answer click! -Jim

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