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Cold Start, Not smooth idle, then "magic reset" and everything is fine (SOLVED)

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1 year 2 days ago #60683 by rgc
Has anyone experienced the following?

2002 Toyota Avalon 172,000 miles

On a cold start, the engine runs smooth until going to closed loop, then Bank1 STFT commands full Rich and Bank 2 STFT commands full Lean. LTFT are very slow to respond if at all. As engine warms up and computer drives lower idle the idle gets, well, not smooth, and kicks on the check engine light. If 1 is a normal idle and 10 is a turn the car off super rough idle, then the engine goes to about a 2 or 3. When the engine gets nearly full warm, the idle drops low, it sounds like the engine is about to falter, and then the magic happens. It is like the computer suddenly realizes it has been wrong and corrects itself sometimes even turning off the check engine light. After the "morning temper tantrum" the engine runs absolutely great the rest of the day whether at idle or max power or anywhere in between. Pending codes from CEL are P0300, P0302, P0304, P0306, P1150 and on rare occasions a P1354 or P1351.

I have attached charts of the Air/Fuel Sensors with O2 sensor readings (right axis for O2 sensor) and another set of charts for the Short and Long Term Fuel Trims. The data collected was over 10 minutes long so I had to break the total data points into 4 charts (e.g. sensor 1, sensor 2, sensor 3, sensor 4) so as to show some detail.

I am a self taught home mechanic just now learning about scanner diagnostics. I have gone about as far as I know how to go and would sincerely appreciate if someone with experience could offer a nugget of advice.

I have twice pulled batter negative and positive cables to reset LTFT and I have twice done the Toyota Idle Relearn procedure. Perhaps it just needs driven so it can learn and adjust??

Thanks

rgc

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1 year 2 days ago #60685 by spit64
When open loop the ECM will not use O2 sensors when the engine gets hotter theO2 sensors to start function sounds like a O2 heather problem measure the heather circuit on the oxygen sensor

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1 year 2 days ago #60686 by rgc
Thank you for your reply. I have thought the same about the sensor heater but am confounded by the "magic reset" as I'll describe.

The Bank 2 Air/Fuel Sensor is brand new. The single downstream O2 sensor is also brand new. Both are Denso sensors. So, I believe it very unlikely that the heating element in both sensors are compromised or otherwise are the culprit.

So, that would leave the sensor heater circuit from the ECM or the ECM itself. I will test the Bank 2 A/F sensor signal and heating circuit soonest as that is very easy to get to. The other two sensors are hard to get to so it may have to be later in the week when I can dedicate some more time to this "project".

As to the "magic reset" shown on the Sensor 4 chart and the Trim 4 chart, once the reset happens, both A/F sensors tighten up around 3.3 volts which is how Toyota A/F sensors are supposed to operate. And, the downstream O2 sensor tightens up around the .8 volts, a bit rich, but still showing operational. To me, it seems odd that all three (3) heater circuits for all three sensors would just happen to "turn on" all at the same time. Or, that all three heater circuits would be malfunctioning together.

Last, after the ten (10) minute morning warm-up and the magic reset, the engine runs perfectly the entire day long. It has no hesitation, good power, no roughness, good idle, multiple engine on/offs, no CEL, no DTCs ... it just runs great as long as engine doesn't cool down to completely cold.

And that is why I sort of, not completely, but sort of feel the sensor heater or heater circuit is not the problem. But to your point, best way to know for sure is to test it with a multimeter.

thanks again!

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1 year 2 days ago - 1 year 2 days ago #60689 by Paul P.

Pending codes from CEL are P0300, P0302, P0304, P0306, P1150 and on rare occasions a P1354 or P1351.


Pendind Misfires on Bank 2 only with VVT codes pending.

This would be my first suspect, VVT system, Engine Mechanical.

P 1351 is a range/performance mechanical code

P 1354 PCM is not seeing a change.

A possibility in this case is there is an intermittant issue happening on Bank 2 VVT system, that is correcting itself, hence the "Pending" codes.

The P1150 AFR Performance Bank 2 can be the effect of the other pending codes.

Never stop Learning.
Last edit: 1 year 2 days ago by Paul P.. Reason: added content

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1 year 1 day ago #60691 by rgc
Appreciate the help!

To P1351, after much research and reservation, I decided to replace the Variable Timing Valve. I bought a Toyota Factory part. That was about 4 weeks ago. It was the first time I have done anything that extensive. Since then, the engine has gone about 500 miles and hasn't destroyed itself!

It still does throw P1351 but only very very rarely now. Now, the codes are always P0300, P0302, P0304, P0306, and maybe about half the time it will throw P1354 and/or P1150. And please know that after the engine does its cold start morning warm up, sometimes, the PCM actually turns off the CEL all on its own.

To your comment on P1354 ... "PCM is not seeing a change" ... I did change the camshaft timing sensor even after testing the original. So, I do not think the issue would be the sensor itself. Perhaps the wiring from the PCM to the electrical connector is an issue? Or could the misfires tend to cause the P1354 code?

Also, I did put in a new air filter, cleaned the mass airflow sensor and cleaned the throttle body and the IAC (poorly on the IAC). It did seem to improve the Long Term Fuel Trims and brought them closer together. The two Long Term Trims used to be much wider apart. But that also could have been the system reset by detaching the battery cables.

Thanks again!

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1 year 1 day ago - 1 year 1 day ago #60703 by Tyler

To P1351, after much research and reservation, I decided to replace the Variable Timing Valve. I bought a Toyota Factory part. That was about 4 weeks ago. It was the first time I have done anything that extensive. Since then, the engine has gone about 500 miles and hasn't destroyed itself!

It still does throw P1351 but only very very rarely now. Now, the codes are always P0300, P0302, P0304, P0306, and maybe about half the time it will throw P1354 and/or P1150. And please know that after the engine does its cold start morning warm up, sometimes, the PCM actually turns off the CEL all on its own.

To your comment on P1354 ... "PCM is not seeing a change" ... I did change the camshaft timing sensor even after testing the original. So, I do not think the issue would be the sensor itself. Perhaps the wiring from the PCM to the electrical connector is an issue? Or could the misfires tend to cause the P1354 code?


Thank you for the data captures! :cheer: Much appreciated.

Which VVT solenoid did you replace? The one in the front cylinder head, or the one in the back (firewall side)? Or, did you replace both?

I'm with Paul about this being a mechanical/VVT problem. These engines run exactly like you're describing when one bank or the other has its VVT solenoid stuck open, causing the VVT to advance all the time. The fuel trims will skew bank-to-bank because one bank of the engine is breathing very differently from the other. Same for the A/F sensor code.

EDIT: I also wouldn't count on the presence of P1351/P1354 to indicate if there's a timing problem or not. I've seen many of these engines with stuck VVT solenoids happily set misfire codes, but almost never set timing codes.
Last edit: 1 year 1 day ago by Tyler.

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1 year 19 hours ago #60704 by rgc
Appreciate your questions!!

So, this has been an on-going problem for at least 8 weeks. This is my son's car. He is a starving musician so I am trying to make the vehicle last for him just a bit longer.

Specifically, when he first experienced the rough idle it was on a scale of 4 - 6 referring to the scale described in the original post. And, of all the DTCs thrown, I focused on the VVT codes first. In focusing on this issue following is what I did, all on Bank 2, the bank nearest the radiator:

1. Took out the OCV solenoid and cleaned it thoroughly. Tested Resistance and in spec but high side of spec
2. Changed Oil and filter (the vehicle has had regular oil changes, was my father-in-law's so I have the history)
3. VVT codes remained
4. Changed the little Oil Screen/ Filter next to the OCV
5. VVT codes remained
6. Replaced OCV solenoid with brand new one
7. VVT codes remained
8. After much thought, I opened the valve cover, took out the camshaft, and replaced the Variable Valve Time Gear with a brand new Factory Toyota VVT (see picture)
9. After all the above, The VVT code now rarely shows up. Though every now and then it said code does get thrown.

Not sure if the above helps with the thought process but sure hope that it does
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1 year 18 hours ago #60706 by rgc
To be more clear, when I mention that "VVT codes remain", please know I took the car out on test drives to see if the problem had been corrected. And, on these test drives, the check-engine-light would come on and flash and the same DTCs would be thrown.

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11 months 3 weeks ago #60811 by rgc
Posting the outcome and the mistakes made so hopefully can assist someone in the future:

When the Avalon started this problem about 8 weeks ago, my son and I focused on DTC P1354. Ultimately, his car, so he decided to replace the Bank 2 Oil Control Valve (OCV). He researched and purchased the Duralast from Autozone part #TS1029.

He came to my house, put in the garage, grabbed some tools and he installed it.

Eight (8) weeks later, after much help from this and other forums, he and I discussed and agreed that the new OCV was the issue. I purchased one from O'Reilly's. It was Dorman part #917211.

He and I compared the two parts and though they look similar, they are different. The two pictures show the Duralast on the left and the Dorman on the right. Both valves are laid over on the electrical connector. Upon closer inspection, it looks like the oil cuts, or openings, are about 180 degrees opposite of one another.

We installed the new Dorman part and now the engine runs great!

In reviewing our steps, we realized we realized we committed the cardinal sin. Neither one of compared the new part to the original part. Had we done so, we would have saved ourselves much time, $$, and stress. I normally do said comparison. But, in allowing him the freedom to manage his own car, he didn't compare and I didn't back him up by insisting on the comparison. I know better and now he does.

Also, please don't nail Autozone. This could be their fault and it might not be. I suspect one of three things: 1) the Autozone website has Bank 1 OCV listed for Bank 2 and is wrong in which case it would be the fault of Autozone, 2) who ever supplies Duralast to Autozone could have stuffed the wrong part in the correctly labeled box therefore not Autozone's fault, or 3) whoever makes the Duralast part completely messed up in the manufacture of the part, again not an Autozone mess up.

I will include in two separate posts right after this the pics with the air/fuel & O2 sensor readings as well as the fuel trim readings with the bad valve and with the good valve in hopes it might help someone in the future.

For me, I learned some new things about diagnostics and removed and installed a camshaft. New skills and confidence were gained.
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11 months 3 weeks ago #60812 by rgc
The following user(s) said Thank You: Tyler

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11 months 3 weeks ago #60813 by rgc
Sensor charts after installation of the good OCV

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11 months 3 weeks ago #60814 by rgc
Fuel Trim charts after installation of the Good OCV
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11 months 3 weeks ago #60821 by Noah
Thank you for posting the resolution to the issue, I'm sure it will help some one in the future with a similar problem.
My last shop used Auto Zone almost exclusively, so I will lay the blame squarely on them. Dura-last-part-I-buy-from-AutoZone.

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