No, that is what it should be reading at idle, while working properly. Cleaning will not change the value, unless it is dirty
The upstream has the final say in fuel trim, so it does compensate for it, but late in the game. It is the "correcter".
agreed, unless he is not at idle or there is a vacuum leak
Near perfect
Really helpful information. To recap. This is the 2.4 i4. I used Protect & Clean and got my first CEL with the car about a week later, so I treated with Cataclean before a planned highway trip. Then I cleaned the MAF sensor and throttle body/plate with CRC. Replaced Upstream and downstream sensors with Denso. Erased codes and am hoping they don't come back. I will now check for vacuum leak and recheck long term fuel trim at idle and at steady throttle. THANKS!
But it's not an engine flush
Use the Gumout Multitune, 1 Oz per qt, drive it for 20 minutes, let it get up to temperature and use the rest in the fuel tank.
New information: Should have checked but there is an accumulation of black soot on the muffler tips, not oily. After cleaning the MAF sensor, there's a slight improvement in readings. From 3 grams/sec down to 2.7 grams/sec at idle (2.4 liter engine). After replacing upstream air/fuel and downstream O2 sensors, long term fuel trim has gone from +0.8% to -8.5%. Short term seems to move around between 0% and -7%. What I take from this, is that the old upstream sensor should have been subtracting significant fuel, not adding it and this has been happening for a while. So "tired sensor" seems likely. The downstream sensor, was probably doing it's job by throwing the P0420 code. I suspect the rich condition is due to a partially clogged cat. I suppose I should get the back pressure measured. The engine is rated @ 200hp and seems to still accelerate the car decently from 80mph, so probably not melted, just coated. No pending or confirmed codes yet and permanent code has not disappeared, but not expected since cat readiness has not completed. I'm trying to add enough completed drive cycles to get something to register. I'm hoping the cat is seeing far less unburned fuel now and may recover? If I do need to replace it, should be better protected now.
Agreed. Seems to me the change from +0.8% to -8.5% means I'm running less unburned fuel into the converter now with the new sensors and everything may be good enough to avoid P0420 returning. Over the 13 years I've owned the car, I've done the following: Shortened OCI, no change in consumption. Replaced PCV valve, no change. Switched to Top Tier gas while adding Techron every few months. This reduced consumption. Switched to high mileage oil. Consumption of 1qt every 3k miles has been going on for years now. In 35 years, this is the only car I've owned that has burned any oil. Then I tried Restore & Protect and probably over-reacted when the engine threw a code and the oil looked "dark". Used Cataclean once after the code came up. Cleaned MAF and replaced upstream and downstream sensors with new correct Denso parts. I'm considering adding more Cataclean at intervals and switching to 0w30 oil and seeing what happens to oil consumption and long term fuel trim over the summer. My PA emissions inspection isn't due until February. Could go with Restore & Protect again. Mobil 1 ESP oil claims to be friendly to cat and sensors if burned. Any opinions?
Car has 125k miles. Oil burning started sometime around 60k miles. Rich fuel mixture is probably a recent development and even more responsible for the code.
Acura sent the letter in 2015, extending the warranty to 8yrs / 125k miles specifically for piston and ring replacement due to excessive oil consumption. My oil consumption never came close to what they consider excessive and time ran out in 2019.
