I have been having a problem for at least 6 weeks with my 2K2 Maxima. Low end torque seemed to be down, the engine was idling really rough and my fuel economy was never above about 18 mpg (I checked this mathematically with every fillup). With my last oil change, the oil was wreaking excessively of gasoline.

I couldn't understand why I car with only 7500 miles would be doing these things. Out of frustration I chose to reset the ECU by unplugging the battery for a couple of hours. After reconnecting the battery and driving the car a bit, I immediately noticed a few things: rough idle is almost completely gone except for an occasional very mild shimmy in the steering wheel, fuel economy appears to be up at least 2 mpg, low end torque feels stronger and the engine is running much much smoother through the whole rpm band. Of particular note is on up shifts, the engine "hangs" at its top rpm more than it has in recent times prior to dropping to lower rpms. This is making shifting much better.

I am very happy that resetting the ECU seems to have resolved my problems but I wonder what happened? The only thing I can think of that might be related to the problem was one day on my way into work, after running the car hard, I lost all power from the engine in the parking lot. It started to run rough and stepping on the gas yielded almost no power and some bucking. There was no CEL though and I simply shut off the car after I rolled into a parking spot. At the end of the day, I started the car up and everything seemed ok, so I kept driving without going to the dealer. I wonder if I might have over extended the throttle pedal and caused the computer to go into Limp Home Mode permanently? Any thoughts would be appreciated.

 

i read the exact same thing in another post yesterday. was that you? or could it have been someone else?

 

I'm pretty sure it was not me, which post are you referring to?

 

then you will have this.

 

heh looks like it was you
Computer MPG vs Actual MPG

i was kind of hoping it was someone else thinking we may actually find out why some of us are getting such bad mileage.

 

Why exactly is this

 

"if your trips are less than 15 mins...
then you will have this."

'this' being poor gas mileage.

 

hmm... wasn't it already established several weeks ago that unplugging the battery will not reset the ECU?

 

i dunno i dont know much about the ECUs. do you remember a specific thread that talked about it?

 

Dudes... funny you mentioned this, cause yesterday my friend told me the same thing about his 95 Max. He said, "I may be crazy, but everytime I reset my ECU (he does it by turning some kind of dial back n forth ) I get better MPG (i think he said like 2) and it runs a little better" He said he's noticed this before... and: "if this is the case, then I feel like resetting it every damn week"

He also has a 2k1 Max (bought recently), but he hasn't tried it there yet. Very interesting observation... why, though?

BTW: He drives like 100mi a day (50mi each way)

G

 

I can't recall which thread it was mentioned but the 2k2's ECU won't reset when the battery is disconnected.

From what i remember, the ECU would just relearn settings after a few start-ups.

 

purrs after a ECU reset. But after 2-3 days of my short trip driving, back to rough idle and horrible gas mileage.

 

Hey, I guess your right. I posted that message before I tried to reset the ECU.

As a side note, it does appear that my average mileage may be going up. The engine is still running much smoother than before and I actually saw the computer register 25+mpg this morning. That's pretty good since I hadn't seen more than 20 or 21 in a long time. Also, I use only premium fuel, Mobil, Sunoco or Texaco. I'm bringing my car into the dealer next week and I am going to find out if they have an updated program for the ECU. If so, I'm going to have the ECU flashed with the latest code. This may help too . . .

Also, disconnecting the battery should reset the volatile ram in the ECU. Of course, the software and any hard coded system defaults will remain for the first startup after the power is reapplied . . .

Thanks!

 

The max used to be very powerful...but it seems to be getting worst.
I mean...a Calviar outrun me from a dead stop..I know i have 2 more guys in the car, but still....

So u really can't reset the ECU for 2002 max? does that mean I screwed?

Anyway, another thing...I'm no expert in manual, (My 1st stick shift car.) But sometimes, when i push the clutch to change gears, the RPM actually goes higher, as if I'm pushing the gas.....is there something wrong, or is that er..normal?

please help!

 

read this. Chinkzilla asks the same question and swallac2 seems to answer it.
http://forums.maxima.org/showthread....5&pagenumber=3