For a complete step by step how to, see this discussion in the Lexus forums:
http://us.lexusownersclub.com/forums/index.php?showtopic=30723&hl=iacv
Different vehicle but same engine. The layout might be a bit different in the Avalon but this will at least point you to the major parts. I suspect everything is the same.
- Thanks for posting this link. I have a 2001 Avalon, 132k mi.
Symptoms: rough idle, CEL, off-idle stumble. minor stumble on highway when entering power enrichment.
It was time for plugs and fuel filter anyway, so I did that - - no change. Did the IAC Valve cleanout procedure as recommended in the link, and the car runs like new again.
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EDIT:
Problem resumed within 20 miles of driving. Took the IAC valve apart again and found some binding on the rotating shaft. I figured this was due to cleaning solvents removing lubricant from the shaft bearing. Lubed the bearing until shaft rotated freely and reinstalled. Good to go again. For about 10 miles, then the rough idle and part-throttle stumble returned. Jumper test on Diagnostic port showed primary IAC to be bad.Installed new Toyota valve and actuator. No change. Wasted $200 on this new part.
All plugs have less than 500 mi. Going to pull them next and look for excessive carbon or fuel (bad coil), or lack of combustion evidence (bad injector).
Will report back.
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EDIT:
Passenger side rear plug showed sooty buildup. Other plugs clean. I re-checked the plugs I replaced (I always put them in the new plug boxes and mark location) and the plug that was in that cylinder prior to replacement was more sooty than others also. Looked like a
weak coil (
failed coil would leave moist residue). Replaced the coil (Autozone Duramax box contained a Denso Toyota part identical to the OEM on the vehicle) and car runs like new again. Will report back only if situation changes.
Could this have been the only issue all along? Not sure, since jumping the Data Connector showed the IAC to be faulty. This car, like my other Toyotas, has been superbly reliable. $300 in parts every few years is not a bother.
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FINAL UPDATE
Damn! I chased this one for a while. After all above changes, STILL had the same symptoms return, including one I didn't mention earlier - engine vacuum could not keep up with repeated brake applications and power assist would diminish. Decided to make one final troubleshooting pass before sending it off to the stealer.
I started with the Oil Control Valves that feed the VVT mechanism. My Haynes says that resistance across the valve terminals should measure between 6.9 and 7.9 ohms, and that even if it passes, put battery voltage to the terminals and check for mechanical operation. When I first started this journey, both tests checked out fine.
For my final effort, the car happened to be at operating temp, and the resistance for both of the Oil Control Valves measured 8.9 ohms. Could heat be the factor? I waited 20 mins and measured again. Both showed 8.5 ohms, then later, 8.1 ohms. Obviously, heat was exposing a problem with these parts.
I purchased two new OCV's from the dealer for $79 each (ouch). They measured 7.5 ohms out of the box.
Installed them, cleared codes, car runs like new.
Hope this helps somebody out there.
