GM 4.2 liter V-6 Deactivation - Page 3 - Fuelly Forums

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Old 07-31-2008, 12:59 PM   #21
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I should have mentioned, I'm heeding the advice of Jay2the rescue, am going with three cylinders in Stage One. Will check the mileage and acceleration to 60 mph. I expect because one O2 sensor will be cold, the computer will call for an enriched fuel mixture, bad for mileage.

Stage Two will have a muffler shop drill, tap, and plug a hole for a future O2 sensor somewhere ahead of the Cat. I will then personally swap the plug and the O2 sensor in the unused bank, as recommended by Road Warrior and Jay. If anyone thinks I would still be in trouble with the government, please so advise.
If you go in for an emissions inspection and they figure out what you did your car would probably fail. The good news is that the vehicle is OBD II so if everything looks OK with a quick look under the hood, and the computer has no faults stored then you should be ok in an emissions test.
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Old 07-31-2008, 01:03 PM   #22
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The easy way to protect yourself is to leave the original one in its place and simply add a new one in the new position, then just switch the wire over to it. When you go for an inspection switch the wire back.

Even better, have a wire attached to each, and the wire from the old one can just go nowhere, but now if someone looks under they don't see anything odd at all.
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Old 07-31-2008, 01:19 PM   #23
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The easy way to protect yourself is to leave the original one in its place and simply add a new one in the new position, then just switch the wire over to it. When you go for an inspection switch the wire back.

Even better, have a wire attached to each, and the wire from the old one can just go nowhere, but now if someone looks under they don't see anything odd at all.
I like the second idea better... If you switched the cable for an emissions test the CEL would come on as soon as the vehicle entered closed loop - automatic fail. Leave an O2 sensor in the original location, with a dummy harness plugged into it.
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Old 08-02-2008, 01:27 PM   #24
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OK, so Phase One is done, and I'n not happy with the results, . . . . yet.

The right hand bank was deactivated, by backing off the rocker arms and shutting off the fuel injectors. No changes were made in the O2 sensors.

I have yet to time its acceleration from zero to 60. With all six cylinders it was 10.1 seconds It cruises just fine on the one bank, but getting there is a problem because it stumbles badly at the start. I don't recall it doing that when I first experimented by pulling the plug wires off one bank. The only difference I can think of is that I had deactivated the left bank, and the mechanic deactivated the right bank.

The way it is acting now, you would not want to try to make a left turn in front of approaching traffic.

I filled the gas tank and I'm going to drive it as it is to make a mileage check before trying anything else.

Stay tuned.
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Old 08-04-2008, 03:13 PM   #25
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I give up. My mechanic is now restoring operation to original. Besides the bad stumble on initial acceleration, the transmission shift point got fairly rough for some reason. Additionally the mpg got worse dropping from 17.3 to about 12 on the first tank.

I suspect the car's computer was the problem. I still think it was a good idea, but maybe someone else can figure out how to do it.
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Old 08-04-2008, 03:20 PM   #26
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I give up. My mechanic is now restoring operation to original. Besides the bad stumble on initial acceleration, the transmission shift point got fairly rough for some reason. Additionally the mpg got worse dropping from 17.3 to about 12 on the first tank.

I suspect the car's computer was the problem. I still think it was a good idea, but maybe someone else can figure out how to do it.
The best thing to do if you really want a car that does this is buy a late model GM car with "Active Fuel Management". GM did this on the early Cadillac NorthStar V-8's but it didn't work well. Cadillac also tried to do it in the early 80's - I'm not sure what engine, but it did not work well then either. The new version GM is selling now actually works, and pretty well too.

-Jay
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Old 08-10-2008, 06:18 PM   #27
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So this will be the last post to summarize my experience.

Early on I pulled the spark wires off one bank, and it ran pretty smooth.

I then had my mechanic back the lifters off the right bank, and disconnect the fuel injectors on that bank.

It started OK but ran ****ty. Had to be careful on the gas feed to keep it from stumbling, and the shift points were very rough.

MPG dropped fro 17.3 on six cylinders, to 12 on three cylinders. Possible reason for that is no changes were made in the O2 sensors.

The good news is it is running fine on six cylinders again.

End of experiment.
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