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Discussion Starter #1
The Grey One was acting up. Was bad enough that daughter switched to driving Blackie.
Symptoms were chugging at cruise (2000 rpm), hesitation from stop and no code, though when t'was very bad, P0171 (lean) was tripped.
What I did, and in this order:
Found MAP sensor was aftermarket. Grabbed three Toyota branded at the boneyard, figured a wrecked car was probably running OK. And three was bettering my odds.
This eased symptoms quite a bit, but t'was not perfect (Toyotas are perfect, soooo...).
Next in line was a set of injectors, again from a good running parts car.
Found the injector seals were harder than calculus, and cracked besides, so definitely an air leak.
Sadly, this, though an obvious problem, didn't ease much at all. But they weren't hard to change, and cheap ($13) once the cam cover came off, and I needed to change that gasket anyway (bad oil leak).
Thinking this through, and mentally inventorying my spares, led me to the forward A/F sensor, again from a good running car.

This is what did it. The A/F sensor was apparently off enough to affect driveability, but not enough to throw a code.

Now she runs like a Toyota - perfectly.

Forward to another 316,500 miles...

Cosmo
 

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I appreciate the info. But this is straight parts changing without any diagnosis. Hope next time you or someone can show a logical diagnosis process.

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Discussion Starter #3
I could argue that there was a logical diagnosis, done in the absence of any codes.
First, I thought about what gives the signal for fuel while at cruise and accel, which is the MAP sensor, and I changed that, and it helped a lot.
Now that the car was nearly right, and the car had 316K on it, the next step, to me, was injectors, as a badly firing injector can also cause chugging.
Finding the hardened and cracked seals was a problem in the making, and I had good injectors, so I changed them.
When that didn't quite do the trick, but that the problem had changed to just chugging at 2,000 rpm, I thought further about what gives a signal at cruise, and that is the A/F sensor.
If this is not logical enough, then it's because I was raised on carburetors, and have to alter my thinking when it's a computer and sensors that give fuel mixture, not a vacuum signal.

Cosmo
 

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Thanks for the reply and further explanation. Maybe I watched too many videos using ODBII and fancy tools to diagnose the problems. So your approach does not appear natural to me. I could be wrong. So welcome others to chime in. This is a good case for discussion.

Since you have a lean code, I would start from checking vacuum leak. This might lead me to find the cracked injector seal. If I cannot find a vacuum leak, I should check injectors to see whether it can spray the correct amount of fuel. If not working, next step is MAP sensor. But it would be really nice if you can figure out something wrong with the aftermarket one. (Can this be done without fancy tools?) At the very end, I might look at that AF sensor but this one tends to be expensive. So some tests should be done first. Access to junkyard and the plethora of Camry's there helped a lot in this case. If it is rare car and parts are expensive, what will be your strategy and things to look for?
 

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Discussion Starter #5
Since a lean code is not specific, and the driveability issues were confined to off idle acceleration and cruise at a specific rpm, I never gave a second thinking of vacuum leak, the symptoms didn't jive.
Cracked injector seals are not likely to give much trouble, unless they are perished, which these were not, just hardened and cracked.
Checking injectors is a troublesome procedure, and not done by very many shops, certainly none near me.
And the A/F sensor was the last item, because the symptoms had narrowed to the point where that was the obvious culprit.
The thing to remmeber here, is that there were two sensors giving trouble, which makes it a lot tougher.
BTW, I did test drive between each repair, so as to isolate what was happening.

Cosmo
 
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