Running rich

[Acercate]

Hello everybody,

I have a 2007 Honda Accord 2.4 and the problem is that my short term fuel trim is negative (-18%) causing my car to run rich.

If I switch off the engine (cold or warm) I have to wait a few minute before I can restart.

The idle is fine until the engine gets warm and the car will eventually stalls if I press gas unless I create a vaccum leak (Disconnecting PCV hose for example).

Fuel pump, fuel filter, sparks plugs, ignition coils, injectors, crankshaft sensor,...they have all been replaced recently.

I suspect a bad O2 sensor but I have no check engine light.

Any help would be appreciated.

 

[F6HAD]

I would go with changing both lambdas and also removing and washing out your cat.

 

[Channel Hopper]

On a much earlier Accord I used to own, the last exhaust box had collapsed inside, idle was OK but the car would run very rich at A road speeds.

Knocking a few holes with a poker up the rear pipe fixed it.

 

[F6HAD]

Good point, give the back box a tap and see if you can hear the baffles collapsed inside

 

[Acercate]

The car has been almost fully restored. Everything is new from the exhaust manifold (4-2-1) to silencers (Fox Exhaust).

The previews line was a noisy single exit 4-1 without cata.

The problem was already there.

I tried to remove the exhaust or to unplug the 02 sensor to see a change. No difference except the noise.

Sensors have been tested comparing them to a clean 2.4 Accord.

All the values where exactly the same except the short term fuel trim. Mine is negative and never vary.

What about the fuel pressure regulator ? Is there any way to test it ?

 

[Acercate]

Looks like my ECU is "Ethanol ready". That's why, using traditionnal fuel, I'm running very rich without any check engine light.
The seller "forgot" to tell me this detail...

 

[F6HAD]

#facepalm