RPM’s won’t go over 2500

[Ali0227]

Hey y’all I have an 04 v6 and I’ve been noticing what I sense as a lower idle when in park or at a traffic light. Then when I go on the highway weather 60, 70 or 80 mph won’t go over 2500 rpm’s even when accelerating to higher speeds, seems like it’s being held back. I also notice a sluggishness lately when trying to pass some cars traveling at higher speed than I never noticed before. I have 135k mikes and original owner. Any help is appreciated. I also think I have a slight coolant leak. I had one years ago but problem was found and fixed. I’ve lost about 3 or 4 inches of coolant over last 4-6 weeks. I refill to fill line and then after a couple of weeks, I notice a loss but don’t see anything on the ground. I always dread the possibility of a bad head gasket with these engines! Thanks all for any input!

 

[MikeinNH67]

I see you posted on another thread about cat converters going bad. One that is bad enough to affect RPM is most likely plugged and will show hotter than the rest with a laser thermometer. I've seen people pull the upper O2's to prove where the issue is if plugged.

Do you have any codes?

 

[miller507]

Plug in a scanner, check values on O2 sensors and coolant temp sensor to see if their in range.

A faulty coolant sensor can cause sluggish performance when you floor it.