Fixed EGR now MPG is lower

[behind-bars]

Another EGR related thread ...

I got the all to common E48 code on my 4.9, I cleaned out the throttle body and the egr tubes and cleared the code, It then came back. I checked into the vacuum lines and 2 of them broke when I was inspecting them. I replaced the connector on the hose that connects to the valve itslef, and also replaced the connector on the TB side of the hose between the solenoid and the TB. I did the test where you press up on the valve diaphram and the engine sound changed and it stumbled a bit.

The solenoid is realtively new, about 2 or 3 years old now, and the valve is still original at 98k miles.

After that work the code has yet to reappear after a week or so of driving, but my gas mileage has taken a sharp hit, went from over 17mpg down to under 15 mpg in light suburban driving, the weather is good and we do not have winter gas belends to deal with here. Route and/or driving style has not changed.

I rechecked all the work and I dont see anything wrong or unhooked, the car runs with plenty of power now on what appears to be a fully functioning egr system, yet its going through alot more gas then before

I checked the plug wires for a loose connection but their wasnt one, the car isnt missing real bad so I dont think I messed them up anyway.

Any Ideas what to look into now? Did fixing the egr cause other problems to worsen and be more apparent?


I have replaced in the last 10-15k miles

EGR solenoid
Oxygen Sensor
Dist. Cap / rotor
All 8 Plug wires

I also checked the FPR, Hose is a little cracked but it doesnt leak.

[HUF]

I think it is a coincidence. Probably they do add some ethanol and would not tell you. The fuel economy should benefit from properly functioning EGR system.

[behind-bars]

Originally Posted by HUF

I think it is a coincidence. Probably they do add some ethanol and would not tell you. The fuel economy should benefit from properly functioning EGR system.

I thought it may be coincidence too, Guess Ill fill up at a different station next time to test the theory. I went to a station I usually go to, didnt see any ethanol mentioned, didnt ask though. Here in Texas I dont think they ever use a winter blend, and only the larger metro areas (not me) have 10% ethanol

I was just annoyed that the drop occured immediately after I fixed the vacuum hoses. Havent driven that far, but far enough to see the decline in my mileage

[HUF]

Originally Posted by behind-bars

I thought it may be coincidence too, Guess Ill fill up at a different station next time to test the theory. I went to a station I usually go to, didnt see any ethanol mentioned, didnt ask though. Here in Texas I dont think they ever use a winter blend, and only the larger metro areas (not me) have 10% ethanol

I was just annoyed that the drop occured immediately after I fixed the vacuum hoses. Havent driven that far, but far enough to see the decline in my mileage

It takes awhile to reset computer after cleaning up TB IF you did not disconnect the battery for a minute.

[behind-bars]

Originally Posted by HUF

It takes awhile to reset computer after cleaning up TB IF you did not disconnect the battery for a minute.

Yeah, I clened the throttle body/ egr several weeks ago and disconnected the battery at that time, I checked and thier still very clean

I think my only option at this point is to drive it and see if it sets any more SES lights to give me a hint to the problem if thier is one, And to refill at a different station and see if the mileage goes back up.

The only thing that may affect MPG that hasnt been changed is the spark plugs, I have 8 new ones if I decide to install them,probably about time anyway, I just didnt go to the hassle before since I was satisfied with the mileage I had been getting.

Just have to wait and see

[behind-bars]

An oddity I noticed, The last few days I have been beating on the car pretty hard. Faster acceleration from lights and just driving faster in general. The mpg computer had risen up to 16 now under the same driving conditions as always.

I thought faster speed and acceleration usually hurt the mileage

I dont trust complete accuracy of the Fuel info center, but seems like it would go down when I'm harder on it, not up.

Any part of the engine that would benefit from higher speeds? I plan on hitting it with seafoam this weekend and triple checking my egr hoses and see if I can resolve this mess, Since gas is on its way back up fast