Any codes?
If your concerned with the fuel trims I'd concentrate on the A/F O2 sensors that are before the cats.

 

Hi. No, there are no codes. When I checked the A/F voltages, I believe both were at 3.3V (This was 2 weeks ago). I can check again but it would have to wait till tomorrow.

 

Only the upstream sensors should oscillate high/low output. The downstream sensors should output a nearly steady flat output.

 

Thanks. Here is my readout of them from this morning. Looks like they're operating fine then?

 

" notice my LTFT's were in the positive double digits, at one point one of them 21%. "
Start with the fuel trims. Positive 21% will lower your MPG.
If high positive at idle and go down at higher RPM then suspect vacuum leak.
Post LT plus ST trims at idle and also while engine at 3000 RPM.

 

I will get some numbers later in the day when I return to my car. I suspected a vacuum leak because I thought I heard a small whistling/hissing sound the past few weeks as well, but I couldn't pin point it. I thought maybe it's just a normal sound. This is my first car so trying to learn .

But with the brief test I did this morning, the fuel trims were in double digits, 11 and 14%, and when I rev'd to 2k RPM, they dropped. I remember specifically 14% dropping to around 10%.

3k RPM? I thought the test is done at 2k. Is it safe for the engine at 3k? How long should I rev for before recording the numbers?

 

3k RPM? I thought the test is done at 2k. Is it safe for the engine at 3k? How long should I rev for before recording the numbers?


Yes it is safe at 3k. If worried then start with 2k and hold for 5-10 sec. Should see a change in ST right away LT may take the full rev time.
Note: Add the LT plus ST to get the total fuel trim per bank.

 

Hi. Okay
At Idle

• Short Term Bank 1: -1.56%
• Long Term Bank 1: 10.94%
• Short Term Bank 2: -2.34%
• Long Term Bank 2: 11.72%
• Total bank 1: 9.38%
• Total bank 2: 9.38%

At 2k RPM for 5-10 seconds

• Short Term Bank 1: -2.34%
• Long Term Bank 1: 11.72%
• Short Term Bank 2: -3.13%
• Long Term Bank 2: 13.28%
• Total bank 1: 9.38%
• Total bank 2: 10.15%

At 3k RPM for an additional 10 seconds after 2k

• Short Term Bank 1: -1.56%
• Long Term Bank 1: 11.72%
• Short Term Bank 2: -1.56%
• Long Term Bank 2: 13.28%
• Total bank 1: 10.16%
• Total bank 2: 11.72%

So now it's increasing, compared to this morning where it decreased?
Edit: Here is an attempt again this time using another app to graph it.
When I went to 2k: Pic
When I went to 3k: Pic

 

Fuel trims look normal enough . Winter gas/driving style/tire pressure/brake drag/wheel bearings all effect MPG.

 

Hmmm well why did they decrease then this morning when I rev'd as opposed to them now rising? Also in those readings, the short term goes more negative, isn't that supposed to pull the long term down with it, not raise it?

These are the closest I've gotten to 10 in a while. Usually I observe them being around 14-16% when I started observing this. Another example is when I had a LTFT at 21.09. These were the values I have screenshotted a the time.

Idle

• Short term bank 1: -0.78%
• Long term bank 1: 19.53%
• Short term bank 2: -0.78%%
• Long term bank 2: 21.09%

2k RPM

• Short term bank 1: -7.03%
• Long term bank 1: 14.06%
• Short term bank 2: -6.25%
• Long term bank 2: 14.06%

I use 91 octane. I don't have a lead foot while driving, and I try to keep the tires at the recommended 30 PSI. I don't hear anything from the wheel bearings. For sticking brakes, hmm, I don't really think I have that. They seem fine and the brake pads are essentially new.

The day that the OBD said the misfire happened is when this happened when my car (video). Not sure if it's related to the discussion, or maybe I was taught improperly how to use push to start? I always held the button down till it started. Here it did this until I decided to let go. Now I've been just pressing it once, and it seems to have gone for the most part with occasionally doing that but not to that extreme, just for a brief moment. The starter, alternator and battery were checked with a tester and all passed. This is what prompted me to start investigating and noticing my low MPG.

 

These were the values I have screenshotted a the time.

Idle

• Short term bank 1: -0.78%
• Long term bank 1: 19.53%
• Short term bank 2: -0.78%%
• Long term bank 2: 21.09%

2k RPM

• Short term bank 1: -7.03%
• Long term bank 1: 14.06%
• Short term bank 2: -6.25%
• Long term bank 2: 14.06%

With these trims suspect vacuum leak.

 

Hi all. I'm new here, nice to meet you all. I have a 2007 ES350 i purchased 10 months ago.
I live in the city and get (lowest) 10.9MPG-12MPG pure city driving. I've read on other forums the past few months people getting around 15-16MPG. So I decided to do some investigating with my scan tool.

I've had a few issues occur around the same time, I'm not sure if they're related, but I'll stick to the focus of the question (unless you all would like to know). I notice my LTFT's were in the positive double digits, at one point one of them 21%. Apparently I had P0300 but never noticed a check engine light come on, and it wasn't on when I discovered it with the tool. It says the code occurred 2 days prior when the car actually started sluggish (when it was a warm engine) that day.

After doing some research I read to look at the O2 voltages on the downstream. Both downstreams sit around .6-.7V.
Here is a pic @ 2k RPM.

I read that O2 sensors should oscillate like a sine wave between .1 and .9V. So I was told yeah my downstreams are dead, replace them. I got some densos. One I couldn't replace, it partially got stripped.I'll take another crack at it when I can, but I was able to do the other. It shows the SAME behavior as the old ones. The impedance with my meter on the old one showed around 14 ohms, so it's in spec I think anyways.

After some more research now I'm seeing toyota's have this as normal behavior with O2 sensors on the downstreams sitting steady at a voltage, since it uses wideband sensors on the upstream instead of regular O2s? Can someone confirm this? Did I waste time with the downstreams?

Some info that may be of use (or not)

• I replaced the spark plugs 9 months ago (not the coil packs)
• MAF sensor and throttle cleaned 9 months ago
• New battery installed 2 months ago
• I checked the spark plugs again 2 weeks ago (only bank 2 plugs since easy to quickly check). The coils had some slight oil on them. (As if you took a drop and smeared it onto them).
• When I changed the spark plugs 9 months ago, I notice some of the threads had black oil on them, one looked like you took a paint brush and painted it! When I checked my new plugs two weeks ago, they don't really have this issue, maybe a super tiny amount of oil.

Thank you for reading 🙂

Downstream O2 sensors should read a steady .5 volts. Only upstream o2's go up and down

 

Hi. Well, I was trying to do a smoke test for vacuum leaks. I had a small rip on the fuel vapor hose at the connection side to the purge valve. I've seen it before and didn't think it was big enough, but pumping smoke in I saw it coming through and it hissing. I made a DIY smoke tester with a jar, bike pump, and incense. Maybe this also explains why I smell gasoline occasionally at startup. The part number is 2382631080 but I can't seem to find it at rockauto.
Would this be the possible reason for the fuel trims anyways?

 

Makes sense for intermittent positive trims.
The rip in hose opens up at times due to engine movement causing a vacuum leak.
If this hose goes to the air intake then a leak in hose will cause positive fuel trims.

 

Hi there! So I got some electrical tape. I wrapped it a few times around the crack tightly, along with some duct tape after and pug it back on. Was much harder to put on after since I tightened it with the tape nicely.

I got some pretty sizeable changes on the long terms I would say!
The Long Term on Bank 1 I was able to get to drop to 5.47%.
The Long Term on Bank 2 I was able to get to drop to around 7-8%

I couldn't record exact numbers as a bad storm started and I had to get inside for the evening. But I should be able to get some tomorrow or the following day. Pretty surprising how much of a change it was, especially on bank 1!

I didn't think of the engine vibration causing an intermittent change like that, you're right!
Here is a pic of the hose.

The thing is I still swear I hear some hissing around the area around the throttle. I don't know if that's just normal sounds from an engine bay.

 

Could be leaking at other end of the split hose.
Best to replace hose and go from there.

 

I took the whole thing off and the other side seemed fine, and didn't feel any suction nor hear it right at that spot. But sure, I can replace it soon! Of course compared to the other vapor hose, its 4x the price. Lol

Driving this morning, I wanted to say it felt less rough but all of a sudden it returned. After a few hours of work, the long term fuel trims were back in the double digits at 16%.

I cleaned the maf sensor, although the readings from the obd seemed to show it looks like its working properly at different RPMs.

The video I showed you with the issue starting. It started again today, so I went to autozone and let them test the system, because last time I couldn't replicate it. Battery good, starter good, then I put turned on a bunch of things to put a load. Wipers, radio, AC, etc. He did the test six time for the alternator, and all 6 times it showed alternator voltage regulator failed, and I saw a reading for 13.1V on his tester. (The service mode for my car shows a vehicle signal of 13.4-13.5 while driving).

Could the alternator not running right honestly cause a lean condition? Maybe poor power delivery to certain systems? Or most likely unrelated?

 

"(The service mode for my car shows a vehicle signal of 13.4-13.5 while driving)."
This is enough to keep engine running normal and battery charged so not contributing to lean condition.
A reading of 13.1v with all electrical accessory is on low side but may not be alternator itself .
Need to do voltage drop measurements on charging circuit. Possible higher resistance then normal at some connection points.
Wouldn't let this detract from chasing the intermittent lean condition.

 

Need to do voltage drop measurements on charging circuit. Possible higher resistance then normal at some connection points.
Wouldn't let this detract from chasing the intermittent lean condition.

I've done this voltage drop test before when I had this problem with my old battery. These were the readings then.
2) had .02V, 4) had .01V. 3 I'm not sure what it referred to (body or firewall). 6) I wasn't sure which is the output wire.

As for the lean condition, not sure what else to do. Cleaned the MAF sensor last night but that's about it. Looked clean anyways. I'm actually planning on seeing a mechanic Monday if I don't figure it out. I don't really wanna spray brake cleaner or whatever to check for idle changes (worried about starting a fire), and I'm worried if I use water I'll use too much. Too paranoid?

I went to one mechanic today my driving school said they send their cars to. But he kept cutting me off and not allowing me to explain. (Maybe because he was busy with another car). Said I'm only saying it's running lean now because gas prices are going up. I said I've had this MPG issue since I got the car.... Then asked me about tuneups, etc. Said too busy to check for vacuum leaks, come back in a week. The cutting me off before letting me explain things annoyed me. Said spark plugs should of been changed at 80k even though Lexus says at 120k, and said because I haven't driven the car a lot after installing them (around 2k miles) is a possible reason.

After that I drove to a shop I already spoke with over the phone. I was driving by so decided to see if they were busy. They were but they had a brief convo with me, at least didn't cut me off and explain some things. Unfortunately their diagnosis guy has left for the weekend and all the other guys were at lunch or working on other cars. So told me again they'll check it out Monday morning if I'd like.

 

A shop with a good smoke machine and diagnostic tech should be able to find any vacuum leaks.
Let us know how it goes.

 

Hi. Hope all had a good weekend.

So here's what happened at the mechanic today.

They did not do a smoke test. For them, they said their scanners were showing LTFT's between 5-8%. He said that was in normal range and didn't want to charge me unnecessarily since he believed there was no signs of a problem. I told him I had those numbers the other day after I fixed the hose, but they then returned to 16-17%.

The second issue about starting, they could not replicate the issue to investigate. They tried driving the car a few times, starting and stopping the engine, but could not get it to happen. Which some days, it does not do. It seems my car wanted to be on best behavior today, lol. .

They were able to remove the stripped O2 sensor and replace it. He did admit he did not check the LTFT until after the O2 change, and another thing I asked them to do. I only got charged an hour's worth of labor.

When I went home I plugged my scanner in. Low and behold, it told me the trims were 16-17% at idle... but after I started driving, the total trims were around 10-12%. For example, a trim can say long term 8, and short term 2-3, so total 10-11%. Though the total trims do drop when I accelerate.

What do you all think?

 

Still may have a bit of a vacuum leak but for a 15 year old car around 10% positive fuel trims is ok.
Not much more i can add.
Maybe you'll see an improvment in MPG this summer.

 

Hmmm okay. Perhaps I'll take a small break from chasing it. What causes it to raise with age, just engine wear? Or was it not treated correctly like using a different octane of gas for example?

Do you recommend anything I can do to keep it in good performance? For example, friend recommended some techron. Autozone had a buy 1 get 1 free deal. I know some people say it's worthless, some say it's not. 10 bucks, wouldn't mind trying it.

Or, should I get a carbon cleaning? For example I noticed the last lexus report from the previous owner in 2019, they recommended a decarb service and a new PCV valve, but the owner declined it.

Edit: They also said to ignore the scan of the charging system from autozone, that 13.1V was fine.

 

You can do services but probably won't improve MPG much.
Older high milag e engine wearing out.

 

Today the starting issue occurred 3 times in a row. I returned to the shop as they instructed. He briefly looked for 5 mins. Of course, the car behaved itself while it was there and there was nothing he can do he said since it's not consistent, but his educated guess was a failing A/F sensor on bank 1 or the maf sensor. . Of course when I left and went to have lunch, the car did it again. Lol.

 

Update: I was reading another post on this website regarding checking the fuel pressure, but people suggested just unplugging the MAF first to see how the car runs on default. Well, the engine completely dies with it unplugged. Did it 4 times in a row. Tried to keep it running, hitting the accelerator but doesn't do anything. P0102 and P0113 thrown. When I reconnected, car started up fine. Any concern? I'm reading conflicting answers.

 

Check fuel pressure with inline gauge to be sure.
MAF disconnect test doesn't prove much.

 

Hello cj1. Thanks for the response. I haven't gotten an opportunity to fuel pressure test yet, cause I need to set up a day at a friends house to borrow his driveway.

But, I decided in the meantime to try to test another system. I tested the brake booster. When I press the pedal down and shut the engine off and see if the pedal remains for 30 seconds, the pedal immediately starts pushing back onto me.

I didn't drive the car today, but I warmed it up. After doing these brake tests, I plugged in my OBD2. At idle, the LTFTs were both around 17-18%.

I put the car in neutral and had the emergency brake on. I pressed the brake pedal to the floor and my short terms went to +15-16%. I also hear a sound if I listen near the pedals. I have a video, listen carefully. Did I find the issue?

Edit: I checked the valve on it, works fine.

 

If brake master is taking vacuum from the intake then internal leak in master will cause fuel trims to go positive.
You could clamp off brake vacuum hose to prove it.