biglg

4 plugs is the minimum anyone should try and unplug. I unplugged 6 and was running on 2, however the power it seemed to generate caused this feeling of the tranny falling out and tires were losing their rubber. The HP and TQ was unbelieveable. I guess that is why they leave all 8 plugged up because it generates to much power and the parts are durable enough to handle the power.

addkev

I can feel the love in this one.

biglg

LOL, Sorry Kevin.

A little to much humor here. I dont know the answer. However it seems Dave says that it wont idle worth a crap at V4, possibly needs a higher idle. I have no idea.

addkev

I agree. And the question was pretty much directed at Dave. And I guess that is the case, but it seems to me that when you are coasting at 25 mph, it is idling at 800 rpm's why should it not idle at 800 rpm's going 0 mph?

73shark

One reason might be that even though you are coasting, the engine is still loaded with A/C, alternator, water pump, transmission, etc. That might dampen bad harmonics.

ZX1100F1

The real reason(s) is that the even though it appears that during coast down the engine is idling it is actually being helped along by the spinning of the torque converter, once the vehicle comes to a stop the idle quality goes to hell in a hand basket on 4 cylinders.

2. At idle fuel usage is next to nothing so there is no real payoff.

3. There is a slight delay to get from V4 to V8 mode and coming off of idle (from a dead stop) the engine would stumble (or bump), it is slight but profound and something that customers would definitely find objectionable, when momentum is factored in the ever so slight hesitation during the transition from V4 to V8 mode is not a factor.

addkev

That is what I figured. I read in another forum that the average V8 idling uses a gallon of fuel in 30-45 minutes. If you think about it 30 minutes is a long time to be idling. Even the longest stop lights are 3-4 minutes.

Black 5.3

GM tuned into the PCM a decelaration fuel cut off (DFCO) so when you are costing down the injectors would simply stop pumping fuel till you hit the throttle again

ZX1100F1

No DFCO on any current North American GM engines except LM7 and LAT hybrid applications.