When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The car has gone about 200 miles since the front head came off for a valve repair. We did a bunch of mostly minor stuff along the way. The car passed Maryland emissions yesterday with a caveat - the readiness for EVAP has never set Maryland is okay with this as long as there are no fault codes and the Catalyst is okay. I did have a code for P0446 (very small) EVAP leak. I cleared the code and put a layer of electrical tape on one hose for the time being. The code has not returned, but I am not 100% convinced I have met the temperature for the EVAP readiness test despite two overnight soaks.
Anyway, this data was from a gentle 20 min drive cycle at speeds in the range of 35 to 55 mph trying to set the catalyst readiness codes (Toyota drive cycle) Each RPM figure is the midpoint of a range +/- 100 rpm taken from 30 minutes of driving.
While not exceptional, they do look about right. As long as the Long Term Trims are below ±10%, there is not much to worry about. In your case, the trims are mostly negative, indicating that the mixture is a little rich, which can be caused by ECU not being adjusted all the way quite yet. Here is a good article about fuel trims.
As for the P0446 code, it is usually caused by a bad EVAP VSV solenoid in the back of the car, near the Charcoal Canister or the wiring coming to it. I've had that code before, and it was caused by that VSV getting jammed with rust. Those can get expensive and they are hard to find used, since it is not the most friendly place for a solenoid, so I came around it by retrofitting a solenoid from under the hood (90910-12196 instead of 90910-12198), which can be found at any junkyard for peanuts, though you will need longer vacuum hoses to connect it.
Thanks, I should have noted these are the sum of the long and short term trims for each bank. There are a couple thousand data points in the file.
Thanks for the thoughts on the EVAP.
The sum? Long and Short Trims are not supposed to be summed.. Short Trim is an immediate response based on A/F sensors, so it always fluctuates, while the Long Trim is what stores tendencies of the Short Trim, meaning that if the Short Trim remains at a certain percentage long enough, it will get stored in the Long Trim, resetting the Short Trim back to zero. For the general diagnostics, you want to look at Long Trims, Short Trims are there more for sensor diagnostics.
I was trying to look at the trim data at various rpm ranges, so I played in excel. I am going to try to be more disciplined about looking at this stuff going forward. I am pretty good with the routine maintenance and what I call the "break fix." The rest is a bit of a mystery I need to get on top of as I will not be in the new car market for sometime.
Those are great numbers honestly. Looks like it’s running normally. Don’t fixate too much on minor differences between banks, as long as you’re not over +-20% it’s good. There is a great video on fuel trim by The Car Care Nut channel on YouTube.
Also, regarding the I/M Readiness Monitor for EVAP, there is specific instruction for passing the test. It will also be reset to Not Ready after clearing a CEL. See the attached file.
Hayk, thanks! Somehow I have been missing the bit at 3,000 rpm. It passed emissions so I am not going to preoccupy myself right now. The Audi is demanding attention….
From a seat of the pants. The Lexus IS running very nicely right now. I have the rest of the Gumout (PEA) I used for cleaning in the tank and am keeping an eye on the coolant level.
I am about a week away from having the mobility necessary to work on the car again and need to get to the passenger side CV boot.
12-03-21, 04:59 PM
Just curious if these fuel trims raise concerns
