'99 Eddie Bauer problems

[manbearpig33]

I have a '99 Eddie Bauer edition with around 117,000 miles on it. I used to get around 16 or 17 mpg but now only get 12. It tends to start hard and chug up hills (works hard, sounds like it misfires, etc.). I have a check engine light on and took it to autozone and the code was P0125. I understand this is a coolant temperature issue, and a sensor or thermostat needs to be replaced. I was just wondering where the best place to start is, and is the error code and poor performance issue related or independent problems? Last time it was in the shop the mechanic said it probably needed new plugs and wires. Thanks in advance!

 

[mistertonylee]

What's your temperature gauge reading? It should be right in the middle between hot and cold. I didn't have the driveability issues you described, but when I changed the thermostat, my fuel economy went up about 2 mpg. Also, if the plugs/wires haven't been changed (they hadn't when I got my car at 96,000), then yes that can cause some serious issues at 117,000.

 

[manbearpig33]

Drove it around for 15 or so minutes and the needle didn't budge from cold. I'll check it again tomorrow when I'm driving more. I checked the coolant and there's plenty in there. If the gauge isn't moving is that the thermostat or sensor? What's the difficulty level in changing out the t-stat in the 5.0?

 

[arkoza63]

takes about an hours time. its not to hard as i replaced the one on my wifes a few months ago. only problem i had was keeping the new stat in place, as it faces the front rather than on top. hope this helps you

 

[mistertonylee]

If you wish to test thermostat vs. sensor, you can close off the hose (being careful not to damage it) between the thermostat housing and the radiator. If you drive for a little while (mine gets to operating temp. in 5 minutes of driving) and the gauge doesn't budge, you probably have a sensor issue whether the thermostat is good or not.

Of course, be careful not to drive too far with the hose crimped or it will overheat.

 

[PowerAddict]

+1 even if your stat is bad you probably have a coolant temp sensor problem.

If sensor isn't feeding back, PCM defaults to -40 degrees, which means it RICHENS fuel mixture.

 

[ridge903]

Very true to what the others have told you.... If your thermostat is bad and is stuck open your truck will not warm up to proper operating temperture and will run with a rich mixture of fuel and causing poor fuel economy... and noticeable performance issues as you are not getting the proper mixture for the peak perfomance of the engine.