Fuel Trim Malfunction

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Fuel Trim Malfunction

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Fuel Trim Malfunction - 3/9/2008 1:11:36 PM

rickhigher

Posts: 3
Joined: 3/9/2008
Status: offline

I just recently bought a 96 Protege LX with 98000 miles on it. A week after driving around the check engine light came on after accelarating quickly. I disconnected the battery to see if it would come back and it did not. Finally, it did come back only after all the I/M monitors were finsished testing. Code is P0170 Fuel trim Malfunction.

The freeze frame data states the following...

Engine RPM- 768rpm
Load value- 21.9 %
Coolant temp- 161 F

Short term fuel trim 1-       20.3%
Long term fuel trim 1-        14.8%

Short term fuel trim 3-     -100.6%
Long term fuel trim 3-      -100.6%

Vehicle speed 0mph
Fuel system 1    CLSD
Fuel system 2    n/a

Any help or recommendations would be appreciated
Thanks

Post #: 1

RE: Fuel Trim Malfunction - 3/9/2008 1:22:49 PM

virgin1

Posts: 4970
Joined: 3/15/2007
Status: offline

I'm not sure I know how to read this data, but it seems that the car is running only slightly rich, and 14.8 doesn't sound that bad to me, at least... 14.7 being nominal?
I am assuming that short term is either cold starting or idle mode.
When I had CELs appear the codes were all screwed up and not truly related to the problem which turned out to be a dirty MAF sensor.
W/98k on the clock, it might be a little more complicated than that (bad O2 sensor or EGR valve,) but I couldn't be sure.
That's the best I can do.

_____________________________

"There is no tool you can buy that will replace experience." - Josh Mills, C.K.DeLuxe

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Post #: 2

RE: Fuel Trim Malfunction - 3/9/2008 1:29:44 PM

rickhigher

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Joined: 3/9/2008
Status: offline

How did you clean the maf sensor.

(in reply to virgin1)

Post #: 3

RE: Fuel Trim Malfunction - 3/9/2008 2:15:36 PM

virgin1

Posts: 4970
Joined: 3/15/2007
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Remove it (obviously,) and used a very careful handled Q-Tip soaked in 50/50 rubbing alcohol. Considering the environment the sensor lives in, it's really quite sensitive. So be very careful when handling, and especially when cleaning it.
I don't know if that'll solve your problem, but it might and it's a quick, easy fix if it does.

_____________________________

"There is no tool you can buy that will replace experience." - Josh Mills, C.K.DeLuxe

(in reply to rickhigher)

Post #: 4

RE: Fuel Trim Malfunction - 3/9/2008 6:41:48 PM

rocweiller

Posts: 10
Joined: 1/18/2008
Status: offline

I'm having same issue/code with my wife's car.. Tried the sensor already and no luck.. Took air filter off blew it and the cover off but still no luck..

(in reply to virgin1)

Post #: 5

RE: Fuel Trim Malfunction - 3/12/2008 5:36:31 PM

rocweiller

Posts: 10
Joined: 1/18/2008
Status: offline

Found my issue I think.. I had a big crack in the airline from the air filter box to the motor.. No light back on yet so I hope that fixed it..

(in reply to rocweiller)

Post #: 6

RE: Fuel Trim Malfunction - 3/12/2008 7:17:01 PM

wsoape281

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Joined: 3/1/2007
Status: offline

if it is running rich, the main deal would be somewhere in a sensor. does the car idle funny at all? if it tends to idle high then low, high then low, over and over, you are looking at an issue with the MAP sensor. if it idles normal, but tends to bog down at times (steady bogging, not intermittent) you would be looking somewhere in the o2 sensors or possibly just a clogged up pre-cat.

lean mixtures would cause a higher idle and would be caused by MAF issues or things like holes in the intake lines. since your car is running rich, i would run through the sensors first and work out from there. just un-plug the sensors one by one and see if the car runs any different. it shouldn't die, but if a sensor is bad, it will not run any different when you un-plug them. just do the sensors one at a time, plugging one back in before you un-plug the other.

if no sensor issues, could be an injector. we will worry about that if/when we get to it.

(in reply to rocweiller)

Post #: 7

RE: Fuel Trim Malfunction - 3/14/2008 2:44:34 PM

rickhigher

Posts: 3
Joined: 3/9/2008
Status: offline

Update:

As of yesterday the check engine light went away. Does that mean it was a temporary malfuction or is the computer just reseting and testing again. I did not try any repairs, I was going to do it this weekend.

(in reply to wsoape281)

Post #: 8