So I have spent the last few days looking around for all this info, and found some, but not all of it. Flame on if you must...but I recently got a CEL for P0400. I read this could most likely be from a clogged EGR tube. I then read that the clogged EGR won't necessarily lead to lowered MPG, which I have had in the last few tanks. I usually get 100 miles to a quarter tank, but now I am at 145 and about halfway through my tank. I was trying to get under the car and see if there was any exhaust leaks, and there is rust on the muffler, and the section right before the rear passenger wheel on the inside (if that makes any sense). Any ideas on why the ****ty MPG or how to get rid of my code? Thanks!


EDIT: Car has run GREAT up until now, and it still does, only im getting 5-6 MPG less than "normal". 144k, new plugs a month ago, got an MAF (which I thoroughly cleaned) from here maybe 2 years ago, never cleaned the TB, only have the P0400 (0302) code, and just put a bottle of chevron techron in my tank last weekend for the first time ever.

 

Im not sure what p0400 is of the top of my head but if its a O2 sensor then it could be messing with your MPG. other than that i dont see how the rust would do anything to effect it.

 

well how is the rest of the car? how many miles? recent tune up? clean maf or tb? any codes? run any chevron techron lately? T

here are plenty of reasons for ****ty mpg, choose one

 

Well, just an update. After running a bottle of chevron techron, about 2/3 through the tank and my CEL turned itself off! I was reading about how this could happen, but it actually did. Ill wait to see if my MPG increases at all.

 

the P0400 code is often caused by a clogged EGR tube that can only be fixed by removing and cleaning or replacing. If the light comes back, you might want to read up on it.

 

http://forums.maxima.org/4th-generat...g-dummies.html

 

P0400 can also be a bad egr temp sensor , exhaust leak , weak or dead battery , stuck egr valve , or clogged egr tube

 

Maybe the light died ? Lol