Drastic MPG drop after repairs

[Silverado12]

Bad mileage and rough idle can also be fuel injectors, but hard to tell.

 

[InvalidUserID]

PCV has been a while. That's on order and I'll slap that on when I do the o2s, see if that helps.

Meh, they replaced the cats on two recommendations from mechanics. It fixed the problem at the time, the shaky idle and hesitation, it's just that now the fuel economy has dropped.

Probably won't get to the o2 sensors and PCV til next weekend since the car is now up at their lake house. I'll keep you guys updated.

And the spark plugs and wires were both Motorcraft, platinums for the plugs as thats what was OEM.

 

[Warstud]

Originally Posted By: InvalidUserID
The spark plugs & wires were then replaced and the symptoms disappeared.

Although the plug and wires are new I would remove and inspect them. Check the continuity of the wires and make sure all the plugs look the same as the normal plug from the NGK site. http://ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

 

[Merkava_4]

How'd they determine it needed new catalytic converters without doing a back pressure test?

 

[Vikas]

Originally Posted By: Merkava_4
How'd they determine it needed new catalytic converters without doing a back pressure test?
Because that gives them the biggest $$$$ for the repair!

 

[InvalidUserID]

Looked at the paperwork at the original mechanic did do the back pressure test. The original shop recommended he could either buy the cats himself and take it to an exhaust shop as he doesn't do welding/exhaust work (the car has a modified exhaust) or he could order the part and have the exhaust shop next door do it. The original mechanic recommended the buy it yourself method as he said his neighbor shop was expensive.