I have a 2001 4.3L V6 in my Chevy Silverado. It seems to be having multiple issues. 1. Service engine light will come on and blink while accelerating on highway but no code is returned when scanned. 2. Acceleration is very difficult. Going up hills I really have to put my foot into it, and even to get it going quickly on the highway I have to fully press the accelerator. 3. The engine has a very high pitched roar when accelerating. Not sure if this is normal with these engines. 4. The engine shifts either late or very rough. The shift points seem to be set wrong, and between 1st and 2nd gear my truck will lurch when shifting. But once again no codes are being returned. The engine also has a dead miss but once again, no code. Replaced the mass air flow sensor, spark plugs, etc., but nothing has fixed it so far. Like I said, I'm not sure if all of these issues are just something these V6's have, or I have a different problem, but so far no mechanic has been able to diagnose anything. Just looking for some guidance on what to fix or what direction to go in. Thanks for any help!
I'd suspect a misfire condition. If it has been misfiring long enough, it may have damaged the converters and they may be clogging up too. Your symptoms sound exactly like this is what is happening. A misfire can also be caused by a vacuum leak. The intake gaskets are known to leak on those engines.