I have a 2005 blazer that I have had for 8 years...my 4th one!! I have an issue with the truck. It seems to be lacking power (slight hesitation like a misfire) when I am climbing a hill with my 2500 Lb. trailer behind. It almost feels like it won't make it all the way to the top. I took it to my mechanic and he replaced the mass air flow sensor. I have not had a chance to try it again on the hill but I have another puzzling issue. It starts fine..idles well, but when I rev it up a little bit to about 1000-1250 RPM it misses and runs really rough. I replaced the rotor and cap a few weeks ago with an after market one from Ebay and now I'm wondering if that may be this problem. I have lost ALL faith in my mechanic as I took it in for this problem and He has charged me $625 and not able to fix the problems that I took it in for. How crucial is it to use AC Delco rotor and cap? What else can I do to try to get it to run properly. The mechanic said that no issues appeared on his scanner and no codes came up other than the MASensor?

 

You need to do all the fuel pressure and leak down tests including Max Pump Output pressure test. This will tell you if the filter or pump is going bad and if the fuel pressure regulator and or spider is going bad. You should already have the updated spider in your vehicle being an 05 so it would more than likely be a regulator or pump going south on you.

 

And yes it is crucial to use AC Delco secondary ignition parts on these engines so if the cap rotor wires and plugs are not Delco change them.