WHEN I hit 4000 rpm engine pulsates up and down

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#11

06-15-2021, 12:25 AM

derf

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Quote:

Originally Posted by RayW

I have a 2002 Saturn SC1 when I rev up the engine now it hits 4000 and a pulsates up and down up and down before anytime I drive it and put a load on it it bogs down.
I've replaced Coolant Temp Sensor, Fuel Filter, cleaned EGR, checked fuel pressure...Pulled top OS sensor above CAT and had same problem....???? Any and all suggestions will be helpful..ty

If your cat was clogged, driving w the front 02 pulled would have relieved the back pressure / flow restriction and you'd have noticed the difference. It didn't.

Drilling two holes in the back of your not blocked catcon simply gave you a catcon with 2 extra holes, a slight loss in backpressure compared to how the vehicle is used to running, and may cause the PCM to throw codes if the flow to the rear O2 is reduced enough that the signal is seen as slow or non-responsive.