geekrunner

Hello All! My 1999 ES300 is being difficult. 290,000 miles, 220,000 on it's recall engine. 4th owner. I am quite handy with a wrench.
We've been living with the CEL on for nearly all the six years we've owned it. When it knocked incessantly and would not go out of Limp mode, I replaced both knock sensors and Bank 1 A/F Ratio sensor, intake manifold gaskets, coolant hose, thermostat, PCV valve, all six spark plugs, cam cover seals and regular oil service. It ran much better but still had CEL on with P0420 code. We just ignored it and moved on.

Now about three years later, the car begins sputtering under acceleration and was hard to start after shutdown. When it was cold, it started and ran like a champ till it got up to operating temperature. Bought a code scanner, and it revealed P0171 code. Determined to get this fixed once and for all (along with a couple of other minor repairs I had no time for) I took it to a local indie shop. They got me all fixed up with the other repairs and a new MAF sensor. They assured me that was all it needed. All the work together was $700, I thought that was fair.

A week later, the code came back and the symptoms returned. Took it back to the shop, they determined the new MAF sensor was defective, installed another one for free and away I went.
Everything ran fine for about a month, then I started getting a bad misfire and a CEL with the code for a cyl 4 misfire. The hard starting after hot shutdown persisted, but it was not consistent. Swapped out coil packs and the misfire went to cyl 2. Bought new Bosch plugs and six coil packs, but for the time being only replaced the Bank 2 coilpacks and plugs. Cleared the codes and it an much better, but still wasn't quite right.

Now done with the long backstory, now to the present. The car now starts cold very easily but idles up around 2000 RPM. Once up to operating temp, idle drops to about 750. At idle, when I put my foot to the floor, it hesitates for a fraction of a second then accelerates like there's nothing wrong at all. No CEL at all, but once in a while I get the VSC OFF and VSC lights. Code reader shows a pending P0171. When I shut off engine and restart, no more VSC lights. I am determined to figure this out.

I read over previous threads about P0171 code and how fuel trim values can help diagnose the problem.On my first attempt to fix, I removed the airbox, snorkels, and throttle body. Cleaned throttle body and IAC valve. Replaced Bank 1 coilpacks and spark plugs. Replaced PCV valve, grommet and hose. Replaced a variety of vacuum hoses that looked suspect. Put everything back together with thin film of gasket sealer on the old throttle body to plenum gasket. Inspected the throttle body snorkels and airbox snorkel,and could find no cracks although they felt pretty stiff and brittle. New air filter and fuel filter (which was a ***** to fix cause I twisted the fuel line in two and had to splice in new fuel line).

Started car, everything ran fine and after a ten mile drive, determined the issue still was not resolved. It ran fine at idle and at high speed, but still hesitated anytime I put my foot in it, and still hard started after shutting it off and letting it set for more than 10 minutes.

After reading alot about fuel trim, I used my code reader to record about 30 seconds or so of live data at idle, 1500rpm and 2500rpm. This is a sample of what I found. All the LTFT on Bank 1 were over 10% and combined LTFT were over 10%, especially at 1500rpm. See below:

IDLE:
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)16.5
Engine Coolant Temperature(¡£F)199
Short Term Fuel Trim -Bank 1(%)3.9
Long Term Fuel Trim - Bank 1(%)14.1
Short Term Fuel Trim -Bank 2(%)0.8
Long Term Fuel Trim - Bank 2(%)18.8
Engine RPM(rpm) 700
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(¡£)15.5
Intake Air Temperature(¡£F)145
Air Flow Rate from Mass Air Flow Sensor(lb/s)0.01
Absolute Throttle Position(%)11.8
Location of Oxygen SensorsB1S12--B2S1--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.645
Short Term Fuel Trim Bank 1-Sensor 1(%)3.1
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.505
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.645
Short Term Fuel Trim Bank 2-Sensor 1(%)0.0
OBD requirements to which vehicle is designedOBDII

1500RPM
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)14.5
Engine Coolant Temperature(¡£F)197
Short Term Fuel Trim -Bank 1(%)0.8
ong Term Fuel Trim - Bank 1(%)35.2
Short Term Fuel Trim -Bank 2(%)0.0
Long Term Fuel Trim - Bank 2(%)38.3
Engine RPM(rpm) 1718
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(¡£)33.0
Intake Air Temperature(¡£F)141
Air Flow Rate from Mass Air Flow Sensor(lb/s)0.01
Absolute Throttle Position(%)14.5
Location of Oxygen SensorsB1S12--B2S1--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.655
Short Term Fuel Trim Bank 1-Sensor 1(%)0.0
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.690
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.650
Short Term Fuel Trim Bank 2-Sensor 1(%)0.0
OBD requirements to which vehicle is designedOBDII

2500RPM
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)17.3
Engine Coolant Temperature(¡£F)203
Short Term Fuel Trim -Bank 1(%)0.0
Long Term Fuel Trim - Bank 1(%)11.7
Short Term Fuel Trim -Bank 2(%)0.0
Long Term Fuel Trim - Bank 2(%)14.1
Engine RPM(rpm) 2586
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1
Cylinder(¡£)38.0
Intake Air Temperature(¡£F)147
Air Flow Rate from Mass Air Flow Sensor(lb/s)0.03
Absolute Throttle Position(%)16.9
Location of Oxygen SensorsB1S12--B2S1--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.630
Short Term Fuel Trim Bank 1-Sensor 1(%)0.0
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.110
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.655
Short Term Fuel Trim Bank 2-Sensor 1(%)0.8
OBD requirements to which vehicle is designedOBDII


My next test was to find any vacuum leaks. I previously tried to find them using starter fluid but I could not find any that way. I then bought a homebrew smoke machine on e-Bay and used it (correctly) today. I located smoke coming from around the Bank 1 camshaft belt area. My first thought was it was coming from the cam seal, but then realized it could be the cam cover. I removed cam cover, cleaned off the rubber seal and cylinder head mating surface, smoothed on a thin layer of black gasket sealer and reassembled. I'm letting it set overnight and will smoke it out again tomorrow.

Any thoughts on what the fuel trim or any of the live data may suggest? It seems the LTFT goes way out of whack at 1500RPM, which could explain the hesitation. I could record some more data between idle and 1500RPM to see when the LTFT begins to go worse. Would a vacuum leak cause the LTFT to be over 10% all the time, or maybe it's over 10% at idle and over 2500 just due to normal wear and tear of a 220,000 mile engine? Any chance the fuel injectors are tired or dirty? I suppose the next test to run would be fuel pressure, which I can do Friday when I can rent a tester from O'Reilly's.

I will report back when I smoke it out again tomorrow. I appreciate any insight,and am prepared to answer any questions.

geek

geekrunner

Progress report: I re-smoked the engine, and the cam cover sealed up perfectly, and no other vacuum leaks detected. Reassembled the airbox, tried to start the car, but it started really hard! I was very discouraged, till I finally got it to start, then ran the CEL code. Error referred to air flow, then I realized I forgot to reconnect the MAF sensor! Once reconnected, car started and idled at about 1000rpm. Drove it for about 20 minutes, parked it and recorded live data. All the LTFTs came in within normal range! The hard hesitation has softened alot. It doesn't accelerate immediately but it is definitely much improved. Now to drive it around normally and see how it responds to restarts.

I would have posted the live data with fuel trims, but I inadvertently forgot to save them

geek

LeX2K

Have you ever looked at or replaced the VVTi oil control valves?

geekrunner

I've replaced the Bank 2 VVT solenoid twice for unrelated issues, Bank 1 has never been replaced, at least I've never replaced it. I've been pursuing the possibility of vacuum leaks first.
Update: car still has a hard start when shut off for more than 10 minutes, but it starts after about three or four attempts, as opposed to the 4+ attempts. And it generally runs better and accelerates from idle better.

Next options: check fuel pressure, maybe swap out the MAF with a junkyard MAF or cheapie new one. Any other thoughts?

geek

AuttiMan

How old is the catalytic converter?

geekrunner

Based on the CarFax, all the cats are original.

geekrunner

May be making a breakthrough! Just finished a fuel pressure check, and only reading 30psi. When increasing and decreasing the RPMs, I see the pressure gauge fall about one to two psi when revving to >2500rpm. Shut down engine, pressure holds at 30. Restart, and pressure drops two psi, then increases back to 30. I have replaced a fuel filter, could there be another fuel filter? This seems indicative of a failing fuel pump, but I always believed fuel pumps either worked or they didn't, no in-between.

fortitude

From the manual

Measure the fuel pressure regulator (car is off, fuel pump activated via active test in techstream.)
Fuel pressure: 304 − 343 kPa (3.1 − 3.5 kgf/cm2, 44 − 50 psi)

If pressure is high, replace the fuel pressure regulator.
If pressure is low, check the fuel hoses and connections, fuel pump, fuel filter and fuel pressure regulator.

Start the engine.
Measure the fuel pressure at idle.
Fuel pressure: 304 − 343 kPa (3.1 − 3.5 kgf/cm2, 44 − 50 psi)
Stop the engine.
Check that the fuel pressure remains as specified for 5 minutes after the engine has stopped.
Fuel pressure: 147 kPa (1.5 kgf/cm2, 21 psi) or more
If pressure is not as specified, check the fuel pump, pressure regulator and/or injectors.

geekrunner

Thanks fortitude!
I rented a fuel pressure tester, attached it to the bank 2 fuel rail via a banjo bolt adapter, connected it, then turned key to On. No pressure increase, but it sounded like the fuel pump was powering up. I then stared car, and it took a couple of seconds before the pressure rose to a steady 32 psi. When I raised engine RPM, the fuel pressure decreased about 4 psi, then back up to 30-32psi after dropping to idle. After shutdown, I got distracted and did not check the stopped fuel pressure till next morning, it was 10psi.

Questions: is it possible a fuel pump can wear to the point it won't pump with as much pressure? Is it possible the strainer in fuel tank can be clogged and affect fuel pressure? Is it just good preventive mechanics to just replace the fuel pump/pump module and fuel injectors? I'm pretty close to just driving it as it is, then as money permits replacing fuel and emission parts as part of a preventive maintenance regimen. I'm still not getting any CEL.(for now).

Another thing that has been bothering me. I used one of those online mechanic advice sites, and the advice I got based on what I told them was 1) the cold start issue is more likely a defective or dirty MAF sensor, and the hesitation under hard throttle is a possible stretched timing belt, and under hard throttle the valve timing is getting altered momentarily then settling down. The "expert" seemed to think that 30psi fuel line pressure was not an issue.

fortitude

I recommend this resource -Toyota TIS - 2 day access for $15(?). Full Tech Manual. The manual gives in-depth analysis and step by step processes to diagnose and repair. I believe it is downloadable/saveable when accessing.
https://techinfo.toyota.com/techInfo...l=ti_home_page
The search function on clublexus sight is excellent as well for researching issues and suggestions.

Regarding parts - Genuine Lexus/Toyota parts can last a very long time. Replace them if the owners manual maintenance schedule says to or if they have been diagnosed as "failed" or worn/out of spec. . I will only use Genuine Lexus/Toyota parts or the original manufacturer of the part (Denso, NGK, etc...) - especially electronic parts...
Aftermarket replacement parts (especially electronic ones) may function poorly in the vehicle but not to the level of throwing a code. I found a local Toyota dealership that will honor online pricing from reputable dealership sites for OEM parts. Other options can be Rock Auto, Amazon, Ebay.

With what I have stated above, I would question the use of the Bosch plug. Also, was the injector OEM/Denso? Was the MAF OEM/Denso? Was the Bank2 VVT Solenoid OEM? With the fuel trim levels, have you noticed any changes in fuel economy?

Fuel pumps can become weak through time and still function. The manual will speak about testing the pressure regulator & injectors. Check that the fuel pressure remains as specified for 5 minutes after the engine has stopped.
Fuel pressure: 147 kPa (1.5 kgf/cm2, 21 psi) or more

As for timing belt assembly, when was it last replaced?

Confirm the parts have failed via the Tech Manual process before you replace them. It will save you a fair bit of money.

geekrunner

All previously installed pieces by me (knock sensors, wiring harness, Bank 1 A/F ratio sensor, Bank 2 VVT solenoid) were Denso. Coilpacks, plugs, and possibly MAF sensor are not. I have a Denso MAF sensor ordered. Based on the CarFax, this car has had no timing belt service, and all parts not replaced by me up to this point are original.

At this point I'm loSING time to work on it. I'll wait till the MAF sensor arrives, install it and see what happens. Considering the shop has installed one that they say was defective, it may be possible the second one is too. We plan on driving this car to Texas and I'd like to make it dependable without necessarily dropping a lot of money in it. I could do the timing belt myself but it's a lot of work and I don't have much free time right now.

Thanks all for your input!

yeskay

geekrunner: is it resolved. what was the issue.

Rudy602

Many people are too embarrassed to post the results of their thread because they deem it something obvious that they should have thought of first before they went into the weeds - like a filter, etc.

crwys

when I had this problem and I was due for smog soon. I replaced the engine coolant temperature sensor, mass air flow sensor and all 6 spark plugs and the code went away. But it can be many things.