Happy Labor Day Weekend Scotty,

I hope this message finds you well in Houston after all the terrible flooding.

I have a 1997 Nissan Maxima SE automatic with 113,000 miles on it. A few weeks ago I filled up 3/4 of a tank at a grocery store with regular and drove between Houston and Beaumont. It was running smoothly prior to the long drive.

On the way back to Houston, it started to idle roughly and the RPMs would drop periodically. I filled up about 1/2 the tank with Chevron premium thinking it might help clear it up. The service engine light came on shortly thereafter.

The car starts fine; however, when it reaches operating temperature it’ll idle roughly every so often and the RPMs will drop and come back. It seems ok at normal driving speeds, but as I slow and come to a stop it’ll go through that idle and RPM cycling thing. It’ll smooth out for a bit and then randomly start acting up again.

I read the codes for the engine light at a parts store and came up with P0171 and P0174. I did an ohm multimeter check of 2 of the O2 sensors and the front is in spec and the rear is a little higher than spec (4.9 vs. 4.3). I also looked in the air box and things looked clear (I have a 6 month old air filter).

I just put in a bottle of the Gumout multi system tune up and filled up another 1/2 tank of premium based on a suggestion from the parts store folks.

Would you have any suggestions on what to do at this point?

Thanks in advance and I hope to hear from you soon.

Comments
No. 1-2
defphatkool
defphatkool

Glad to hear you missed the water and not surprised people are trying to save their flooded cars. Thanks a bunch for the suggestion. I hadn't changed the filter since about 60,000 miles so I'm hopeful that's the issue. I'm not sure if the parts store has my filter in stock. How long can I run on a bad filter before it hurts the pump?

ScottyKilmer
ScottyKilmer

Editor

Yep, I'm on high ground. Fixing flooded cars now. Often a worn out fuel pump or clogged filter causes those lean codes, as can a bad maf sensor or vacuum leaks. I'd guess filter and or pump, pressure test the pump after changing the filter

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