Oldblue

Doubt our safe advice, and take your chances, preventative work will keep it running, ignoring the noises and such , well some have paid the price with bent valves and damaged pistons, so you gotta ask yourself, do I feel lucky? Well do ya!!?

Blue_SS

I wish you well.

This modification is not one that most would object to, though. Your valuation equation may need another adjustment term or two to account for the change in value... possibly a magnification term.

NoHPbutalotofheritage

Update:

ENG PWR REDUCED returned as well as codes for lean system, O2 sensor inactivity/low voltage, and multiple/random cylinder misfires. Also, the car has a hard start and studders violently/stalls.

Observations:

Blue exhaust smoke filling engine cabin via exhaust manifold gasket. Hmm...

Conclusions/FIX:

I just want to say that my JB Cold Weld/Muffler Tape/Aluminum Clamp over the first crack in the exhaust manifold never broke; in fact, it was so good I believe that the gasket couldn't handle the additional stress and finally disintegrated.

Replaced Exhaust Manifold/Gasket, Flex Joint, Spark Plugs, upstream O2 sensor and sounded like a Ferrari first crank. Problems haven't returned to date. For fun, checked fuel pressure at rail as well as each injector; pressure was in spec and injectors had correct resistance and could hear flow through screwdriver. I am thankful GM made the injectors so accessible. Even though my plugs were fairly new, I switched them out in case of fouling from running lean/rich.

Hope this helps.

donbrew

I just re read the thread. In post # 8 you said this in regard to the ignition recall:
The recall has absolutely NOTHING to do with the throttle body or risk of fire. It IS about the ignition switch up and turning off for no reason. Which will cause the the O2 sensor to stop working, the throttle to stop working and any other sensor to stop working. The sensor ref voltage is directly controlled by the ignition switch.

I think a Ford truck recall had something to do with the ignition causing fires.

NoHPbutalotofheritage

You're right, I am going to have the recall work done. What I was talking about was the "Eng Pwr Reduced" Mode in the quote you're referencing there.

donbrew

The eng power reduced does not have anything to do with a malfunction in the throttle. It is telling you that the computer has diddled with the injectors and timing to reduce power so the engine won't explode.

NoHPbutalotofheritage

The Eng Pwr Reduced certainly is directed to throttle. If TPS sensor fails on throttle body, it will not send correct voltage to computer. That will trigger "Eng Pwr Reduced" immediately.

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NoHPbutalotofheritage

There are several threads on TPS triggering reduced power mode, it is the most common problem. In my case though, it was a bad exhaust manifold messing with fuel/air mixture.

Oldblue

Great problem solved! Yeah!

donbrew

As I said; A bad ref for the TPS and APP causes a fault, so the computer reduces power so you can't blow the motor up.

The computer can only control the fuel supply, that's why fuel trims are so hard to understand.

For instance; if you have a cracked flex pipe the #1 O2 sensor can read lean so the computer will increase the injector duty cycle causing a rich condition. Or, it can read rich so it reduces the cycle causing a lean condition. Either of those would cause the computer to go into reduced power mode if the conditions are right. Sometimes a crack will admit air (too much Oxygen) into the system making the sensor read rich sometimes exhaust gasses escape before they get to the sensor (not enough Oxygen) causing a lean reading.

Any sensor can short internally causing the entire ref circuit to go bad; engine power reduced mode. In a computer driven car everything that you used to call a switch is now a sensor. There are 2 ref circuits, the APP and TPS use both of them, other sensors use one or the other.

Many faults can cause a reduced power mode, the message tells you that it is activated, not that it is sensing a reduction in power.

Much more complicated than that, but for us amateurs enough.