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2005 Chevrolet TrailBlazer LS 4dr 2WD

2005 Chevrolet TrailBlazer
Trim Info:
Rear Wheel Drive, 4 Door
16 mpg city / 21 mpg hwy
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November 23, 2012, 11:30 am

Michael A

Question: terrible fuel economy

I have recently purchased a 2005 trailblazer LT 4x4 with 105,000 miles on it. It has a 4.2l and runs excellent other then the worst fuel economy ever. According to the dash Im getting 10.2 avg miles per gallon. IT sucks fuel like a dragster. This truck is by no means a dragster. I changed the air filter what should I do next? Please help

December 1, 2012, 10:19 am

Ron W
Expert Mechanic

Start by getting a scantool and clearing the codes. It will reset the fuel adaptive strategies back to factory. That may improve fuel economy all by itself.

Don't do this if you are about to have a smog inspection as it will reset all monitors (computer self diagnostics) which take a bit of time to set. and in most state the monitors must have run to pass the state emission test.

For all hard starting or engine performance issues, you should always start with the basics. Make sure the tune up items are done and check the charging and starting systems. The engine must have the basics done in order for it to be able to run correctly. Many things can cause this type of problem, and the simplest sometimes get overlooked.

1/1 users found this helpful.

December 1, 2012, 1:51 pm

Michael A

Thanks for theadvice. I cleared the codes and the chek engine light came back on within fifty miles. It says it has a faulty speed sensor. Coiuld this be effecting fuel econy? Also if i disconnect the battery will that reset the computer? Thanks for the help

0/0 users found this helpful.

December 1, 2012, 5:49 pm

Ron W
Expert Mechanic

The speed sensor code can definitely effect fuel economy. If it sets a code for it, the vehicle may go into limp mode which basically puts it in a rich condition all the time.

And resetting the battery doesn't clear the codes unless you leave it off for a long time (until the capacitors discharge in the PCM) Code checkers that you can buy at most auto stores and Ebay for less than $50 can clear codes as well.

1/1 users found this helpful.

December 1, 2012, 6:03 pm

Michael A

Thanks again i will replace the sensor and reset the icomputer. I will let you know whay haopsns. Yhanks again.

0/0 users found this helpful.

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