'05 Lexus 4.7 Long Fuel Trim report

D

dblshock

Joined
Apr 24, 2007
Messages
4,038
Location
WI.
LONGFT1 -6%
LONGFT2 -8%

This was the avg. on my 50mi. cruise over flat pavement, never went positive only even more negative as I accelerated. Motor seemed smooth and strong, fuel mileage good.

I'm new to this info, from what I understand ideal numbers should be close to 0 with all -/+ readings...what should I glean from my data?
 
Nothing to get excited about, First thing I would is....Stop putting 2-Cycle oil in the fuel. Followed with cleaning the injectors with some Top Engine Cleaner (NOT in the fuel tank!) Change the oil, Clean the MAF, Then reset the Fuel Trims.

I assume the air filter isn't restricted?
 
This run only was E091 no oil...55-60mph low wind....air filter is Aisin maybe 10k I'll take it out for a look, make sure it's seated, clear of obstruction...negative fuel means air restricted?
 
Negative means correction for overly Rich mixture, These are averages per a 4 cylinder bank & both the banks are showing a negative correction.

A restricted air filter can cause this, But not likely given the miles on it assuming you're not operating in a dusty environment?
 
next to no dust here (U.P. forest), my road is paved to driveway...I was getting a code for secondary air pump but I cleared it months ago and hasn't come back, that light appeared only after the car was moved several times maybe 50ft. in the yard over weeks not taken out on the road, super short trips...I wrote it off to that.

My BlueDriver also reads the MAF sensor, again, not sure what I'm looking for there either but that sounds like something that's never been cleaned.
 
It's best to be less than +/- 5%. Your engine is running a little rich and as indicated by your fuel trims, the computer is backing off some with the fuel. It would be more helpful to post more information to see what your various sensors are outputting.
 
Last edited:
My truck (05 Silverado) has been +5-10% or more since I put torque pro on it in the spring. I've run TCW3 in it many thanks and that had zero effect on my fuel trims (if you're suggesting it makes them run rich). In my case it's running slightly lean, especially when coasting it goes 12-15% +, indicating a possible vacuum leak which u haven't found yet

Recently though I had to scan and clear both the company work trucks (a 2013 Silverado, 2010 Tacoma) and both were running on the rich side (-5% or so), then I scanned my friends new 2011 Sierra because he has a cold start miss. It had no codes and also was running -5% or so at idle. It was getting very good average fuel mileage according to the dash (19mpg).

The other trucks both had evap codes which haven't returned yet. So 3/4 ran slightly rich, with my truck being the anomaly. I can't explain any of these but thought it might be interesting.

Probably nothing to worry about into its in the double digits. My truck is while coasting but no other symptoms or codes. The tailpipe is completely clean, nothing but water and ice building up in it.
 
Fun stuff, I guess...monitored the MAF at 60mph on cruise flat road it read 4.5-5.0 ft/min.
no clue what to make of this. Had Lexus on the rack today for tire rotate, axle lube and A/T spill/fill mechanic showed me how to clean the MAF sensors
 
dblshock said:
Fun stuff, I guess...monitored the MAF at 60mph on cruise flat road it read 4.5-5.0 ft/min.
no clue what to make of this. Had Lexus on the rack today for tire rotate, axle lube and A/T spill/fill mechanic showed me how to clean the MAF sensors
Click to expand...
I'll check that one tomorrow when I'm driving my truck, but I think mine was very close to that. I cleaned my maf as well, didn't notice any change afterwards. Amazingly the MAF seemed perfectly clean after 192k miles and 15 years.
 
It’s running a little rich, I’d probably just keep an eye on it.

If it’s running rich it could mean a few things...leaking injector, clogged air cleaner, perhaps faulty upstream O2 sensor. heck it could actually be a vacuum leak and the computer is running rich to compensate. Could be a misfire, but you said it’s running smooth. That’s the key..it’s running smooth.

My 2018 Silverado was running -24 for the first 10-15 minutes upon startup...then it would hover around -7. But I was getting misfires...it was fuel injectors. Yours is running right.
 
doublebase said:
It’s running a little rich, I’d probably just keep an eye on it.

If it’s running rich it could mean a few things...leaking injector, clogged air cleaner, perhaps faulty upstream O2 sensor. heck it could actually be a vacuum leak and the computer is running rich to compensate. Could be a misfire, but you said it’s running smooth. That’s the key..it’s running smooth.

My 2018 Silverado was running -24 for the first 10-15 minutes upon startup...then it would hover around -7. But I was getting misfires...it was fuel injectors. Yours is running right.
Click to expand...
A vacuum leak will drive trims to the positive side. A leaky injector is possible as you mentioned and I would try a good injector cleaner and check the air filter.
 
Think of it in a very simple way. - numbers mean the ecm is subtracting fuel meaning the AF monitor/ upstream O2 is sensing a richer mixture, a + reading means it is adding fuel as it senses a lean mixture. All this adding and subtracting is about the ecm trying to keep the air fuel ratio in the optimal stoichiometric ratio.

On V engines most modern vehicles use 2 upstream and 2 downstream sensors (some older engines use only one of each), these will be referred to as bank 1 and bank 2, this is good because if both banks have the same reading the cause will be something that effects all the engines cylinders not just the ones on the left or right so something like a single dripping injector would not be the cause of - numbers on both banks just the bank the injector is in.

There are some good books that may help you get a better understanding of what all the scan tool readings mean and why.
This one is used by many trade schools.

Automotive Technology: A Systems Approach, 5th Edition: Erjavec, Jack: 9781428311497: Amazon.com: Books

Automotive Technology: A Systems Approach, 5th Edition [Erjavec, Jack] on Amazon.com. *FREE* shipping on qualifying offers. Automotive Technology: A Systems Approach, 5th Edition
www.amazon.com
 
Lubener said:
A vacuum leak will drive trims to the positive side. A leaky injector is possible as you mentioned and I would try a good injector cleaner and check the air filter.
Click to expand...
You’re right, I was more thinking in terms of...you’d think it would cause positive fuel trim but depending on the leak it could cause it to go too rich and then take fuel away.

Now that I’ve written that, it doesn’t make sense. And you’re right.
 
boom10ful said:
My old Santa Fe had around the same negative long term fuel trims. I replaced the MAF and the fuel trims went and stayed at 0 to 1.
Click to expand...

Interesting, I'll try and clean the wires first now that I know where to look...it's the constant negative that is bothering me to achieve optimal stoichiometric ratio 473 or whatever it is, the vids I've seen show LTFT bouncing between -/+ at no more than 5 but when it's said and done equaling 0.

No doubt the motor runs good now but if I can achieve optimal without breaking the bank I'll split those hair.
 
Trav said:
Think of it in a very simple way. - numbers mean the ecm is subtracting fuel meaning the AF monitor/ upstream O2 is sensing a richer mixture, a + reading means it is adding fuel as it senses a lean mixture. All this adding and subtracting is about the ecm trying to keep the air fuel ratio in the optimal stoichiometric ratio.

On V engines most modern vehicles use 2 upstream and 2 downstream sensors (some older engines use only one of each), these will be referred to as bank 1 and bank 2, this is good because if both banks have the same reading the cause will be something that effects all the engines cylinders not just the ones on the left or right so something like a single dripping injector would not be the cause of - numbers on both banks just the bank the injector is in.

There are some good books that may help you get a better understanding of what all the scan tool readings mean and why.
This one is used by many trade schools.

Automotive Technology: A Systems Approach, 5th Edition: Erjavec, Jack: 9781428311497: Amazon.com: Books

Automotive Technology: A Systems Approach, 5th Edition [Erjavec, Jack] on Amazon.com. *FREE* shipping on qualifying offers. Automotive Technology: A Systems Approach, 5th Edition
www.amazon.com
Click to expand...
One thing I'm not clear on.... can evap leaks cause fuel trims to go and stay high?
 
After watching a few more vids on MAF cleaning think I'll just buy a bottle of rubbing alcohol and soak the sensor in a plastic bag then let it dry good..I'd bet this is the issue based on the report above from boom and the fact that my idle is very high when cold started (I thought was normal)....a new Lexus 22204-0F030 sensor looks to be $80 and can't find the Denso sku crossover? could be Hitachi?
 
dblshock said:
After watching a few more vids on MAF cleaning think I'll just buy a bottle of rubbing alcohol and soak the sensor in a plastic bag then let it dry good..I'd bet this is the issue based on the report above from boom and the fact that my idle is very high when cold started (I thought was normal)....a new Lexus 22204-0F030 sensor looks to be $80 and can't find the Denso sku crossover? could be Hitachi?
Click to expand...
I think the high idle is a Toyota thing. At least on Tacoma's like the 2010 at our work. It's always idled high and slightly erratic when cold.

Btw my MAF reads in grams per second instead of the feet per minute you were getting. Not sure how to convert that. I was getting around 29 g/s cruising at steady speed. Around 5 at idle I think.
 
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