Fuel Trim Reading Stuck? Still No Luck!

[uncledave11]

Hello to everyone. got a real stumper i've been after. Recently had my 99 ES300 start running really rough (very sudden) Now after going though all the sensors, cleaning out the VVT actuators and testing of course, cleaning the VVt oil filters, removing the Idle air control and cleaning (that was sticking some), cleaning out the throttle bodies nicely....whew. now it runs and idles 99% better with just a touch of hesitation off the line. You can floor it and it goes like a scalded cat to 100! My big concern. I feel a tiny bit of mis fire (no codes) sometimes at 40-50 mph and then gone. The code reader in live mode show all the O2 sensors working within there voltage ranges but... the STFT for Bank 1 sensor 2 reads 99.2% all the time. The other two are making trim corrections but this one keeps reading 99.2% . Anyone got a clue whats going on here? Both upsteam O2 sensors were replaced about 8k ago. Help!

I've reposted this as I've been really trying to nail this down. I randomly get codes such as the normal random misfire on 2,4,6 with a P1354 (cam timing fault, have replace belt and all in good order there) and some time a P1150 front (radiator side) A\F sensor. Help!!

Thx

uncledave11

[uncledave11]

Well, I didn't see any replies for a fix so I continued to search the blogs and any other info on way could be going on here....and...I found the solution! This might be of value to other ES300 owners that have spent time & money in only to have the problem re-appear! I've learned a great deal about VVT in relation to air fuel sensors and how criticle the oil control valve must operate to keep the engine performance at optimal. The ocv's are really quite simple in operation but are very, very precision in construction. Time and ware will take it's toll on these no matter what oil you use or how well you keep up the preventive maintenance on your engine. They will operate with less and less efficiency util the day comes when you suddeny notice your engine running rough and throwing multiple codes that lead you and your mechanic on a merry chase. I revisited the culpret after several removals, cleaning and testing like the manuals say. However, it wasn't time I took the valve out and put it on my variable DC power supply, that I truly was able to observe it's operation! In the process of "ramping" up the voltage to move the slide inside the valve, I felt slight notchy movement instead of a smooth progression. You can't feel this when using a small screwdriver to move the piston to check for sticking even after cleaning! After repeated cleanings with solvent with the valve held open, I now noticed a smoother but not perfect progeressive movement from 0-7 volts DC applied. After reinstalling the valve and clearing the ECM no codes have been set after 30 miles of driving! Still, I ordered 2 new ones from Rock Auto due to the fact that these are still worn and I need to restore precise control to the VVT circuit if I want the engine to perform to it's maximum efficency. Hope this help's anyone out there that is as frustrated as I was!

[uncledave11]

Hello to all...here's an update to the final fix. I watched the front (radiator side) A\F sensor voltage and noticed after a while on the highway is got pretty unresponsive compared to the rear one. So...Being it was the original I replaced it with a Bosch 15217 wide band sensor. My local parts store beat everyone else's price ($155 out the door), so I swapped it out, cleared the ECM and proceeded to drive and see the results. The engine ran beautifully for about 40 miles with repeated stops, cycling the ignition to add as many start up cycles as i could. Al well well until suddenly the trac light pops on and about 30 sec. later goes off. Then about 2 minutes later the engine jerked while running about 30 mph and rolling up to a stop sign, began it's same old trait of idling badly. No check lights came on and I returned to my garage. Reading the codes now showed a P1354 (Valve timeing circuit) error so I'd have to wait for the new OCV's to come from Rock Auto. This past monday I swapped out the new valves and noticed one charactoristic of the piston movment on the front valve i was replacing. Compared to the new valves this one had a slight "friction snag" feel to it as I gently pushed on it to open it against the return spring. I'm confident now that even though a valve checks good for ohms and actuation with a 12 vdc source, It may bind just enough to cause the valve timing to be "out of sync", so to speak, with the rear camshaft! This would explain why the engine would run great for a while until the parameters learned triggered a failure and could not correct it due to the ocv sticking at various positions! Hope this helps others!