Significant mpg decline has occurred in the last.

DIANE J

MEMBER
2007 JEEP GRAND CHEROKEE
100,000 MILES

Significant mpg decline has occurred in the last month, I have done a tunes up, check brakes, air pressure. Is there any thing else that would cause a decline mpg? It appears to continue to decline.

Tuesday, November 27th, 2012 AT 3:33 AM

5 Replies

RACEFAN966

MECHANIC
5,029 POSTS

Is the engine light on? You say you did a tune up what did you replace? I wouldn't hurt to get a can of seafoam and put it in the gas tank next time you fuel up.

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Tuesday, November 27th, 2012 AT 3:36 AM

DIANE J

MEMBER
3 POSTS

Engine light is not on. I have tried seafoam. Tune up included spark plug changed and belts.

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Tuesday, November 27th, 2012 AT 11:01 AM

RACEFAN966

MECHANIC
5,029 POSTS

When you replaced the plugs what did they look like ie- black, white or? Have you replaced any other parts? Which engine is in it? How is the power?

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Tuesday, November 27th, 2012 AT 3:52 PM

DIANE J

MEMBER
3 POSTS

Dont know the color but I have not replaced anything recently. Power is okay. The rpms are normal. V6 engine. I did have the trans module replace in January

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Wednesday, November 28th, 2012 AT 3:34 AM

RACEFAN966

MECHANIC
5,029 POSTS

I do believe that this Jeep has a mass air flow unit. What I would like you to do is buy a can off mass air flow cleaner and then remove the mass air flow and spray out the inside of it (cleaning it) and put it back and let me know how that does. If the sensor wire inside it dirty or? Then that can reduce the mpg and sometimes alot.