High fuel trims

[Nate Tidwell]

2009 Honda Civic LX 1.8L (R18A1). 294,000+ miles

I've noticed while scrolling through torque pro that my Short and long term fuel trims are the same and excessive at -71.88%. it throws a P0420 code and sometimes a P0302. I have recently replaced plugs and the P0302 hasn't come back. Odd issue on those, on cylinders 1 and 2, the plugs back out even though they're torqued to spec.
What should I look at?

 

[Nate Tidwell]

I guess permissions are not allowed to add images in this thread. I can't upload screenshots here

 

[Fix4Dirt]

I guess permissions are not allowed to add images in this thread. I can't upload screenshots here

host o photobucket or imgur etc and paste them here for non elite you have to host rhem wlsewhwre

 

[Fix4Dirt]

2009 Honda Civic LX 1.8L (R18A1). 294,000+ miles

I've noticed while scrolling through torque pro that my Short and long term fuel trims are the same and excessive at -71.88%. it throws a P0420 code and sometimes a P0302. I have recently replaced plugs and the P0302 hasn't come back. Odd issue on those, on cylinders 1 and 2, the plugs back out even though they're torqued to spec.
What should I look at?

just spitballig but it could be

missing prior maybe before plugs changed
bad o2
or cat

 

[Nate Tidwell]

@Idle

@65mph

 

[96eb96]

Huge vacuum leak? MAF sensor dirty? Exhaust leak near 02?Fuel Delivery?
What is the fuel trim at 1500RPM off idle?

 

[96eb96]

I noticed it is negative. That means subtracting fuel. Leaking injector?

 

[Nate Tidwell]

Almost anything is possible. There are no huge vacuum leaks. It'll run smoothly usually, no surging. mpg is crap right now. Rated for 35+ highway, should be able to get at least 350 per tank. I'll be lucky to hit 250 this tank. And I'll check after work at 1500rpm

 

[Nate Tidwell]

 

[94Eddie]

It is odd that LTFT and STFT are tracking exactly to the 100th. These should be independent numbers that are not in sync. LTFT should adjust and then STFT is closer to zero than LTFT under normal operating conditions. I am not sure what would cause them to sync to the exact value. Especially one that is this far off zero.

 

[Nate Tidwell]

It is odd that LTFT and STFT are tracking exactly to the 100th. These should be independent numbers that are not in sync. LTFT should adjust and then STFT is closer to zero than LTFT under normal operating conditions. I am not sure what would cause them to sync to the exact value. Especially one that is this far off zero.

Agreed, btw, I'm getting more replies here than the civic forum lol. For sh!ts and giggles I'll try different software tomorrow

 

[94Eddie]

Agreed, btw, I'm getting more replies here than the civic forum lol. For sh!ts and giggles I'll try different software tomorrow

All ICEs run on the same general principles so many times the diagnostics follow the same line of reasoning. IMO, if the LTFT and STFT numbers are accurate then I don't think the engine would be running good enough to move the car, if at all. You might try disconnecting the MAF and see if this effects the trim values. If the trim readings move to being closer to normal then you might have a bad MAF or a very dirty MAF. Other things to check is fuel pressure, vacuum leaks etc. Sometimes you can find vacuum leaks by spraying starter fluid around the intake tract, intake manifold, vacuum lines etc. If the idle increases when you spray in a certain area then that area has a vacuum leak.

 

[Nate Tidwell]

Might be time to get rid of torque pro

 

[Nate Tidwell]

At about 1500rpm, the ong term and short term read identical again

 

[Josh P]

How's the exhaust system? A leak upstream of the 02 sensor will kill the mpg but the engine will run ok.

 

[Nate Tidwell]

I'll have to look when I get home. Upstream sensor on these bolt into the catalytic converter that bolts to the head. The exhaust manifold is part of the head.
I'm @ work for the next several hours and apparently there will be rain, possibly storms later too. So I'll pull the explorer out of the carport and pull the Honda in.

 

[94Eddie]

At least the trim numbers being reported are way more reasonable. The first screen shot is what one would expect for LTFT and STFT. The second one is still wonky with them be identical. Are the two screen shots taken using different programs?

 

[Nate Tidwell]

The last set were different from the beginning shots where I was using torque pro (black background).

 

[96eb96]

yeah, those first numbers would absolutely have a CEL.
New numbers seem passable, but still a bit negative. It is subtracting fuel because more fuel than normal is going in.

Not sure if you have wideband o2s on there, but usually there would be a code set if they were bad.

Run a good cleaner thru it (e.g. Techron, something with PEA).

 

[Nate Tidwell]

I have 4 wire, heated narrowband