CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Cylinder deactivation

I have a 2007 chevy Z71 1500 with 5.3 V8. I was wondering if there was any way to bypass cylinder deactivation to leave engine in 8 cylinder mode. I recently replaced # 7 cylinder lifters due to lifters not getting oil in 4 cylinder mode. I can see this will be an ongoing problem and can not afford 3500.00 dollar shop bills. Thanks for any help

That is controlled by the ECM. There should be a tuner calibration out there to give you 8 cylinders all the time. However that will kill your warranty and fuel economy.

Where would I find a tuner calibration? Truck has 116000 miles so already out of warranty.

Search under Chevy performance calibration. There are companies that sell you a module that you use to load their cal. The module also stores your original cal in case you need to go back. The company doing this for Dodge 6.7 Cummins is called bully dog.

Thanks just emailed bullydog to see if they could help.

Hi, I’m new to these forums, and more than 20 years has separated me from the automotive field, but maybe some one could explain how cylinder deactivation is tied to engine lubrication? I would have thought that engine lubrication would continue as normal regardless of how many cylinders are firing. I would have thought an issue of this type would be a lifter going bad simply due to high mileage, low oil pressure, or an oil journal that is plugged up a bit.

De activation leads to low temperatures and generally the moisture accumulates and lets the crud build up. If you operate under low loads for short times, this will happen to every engine. However the deactivation makes it worse.
It would help if they rotate the firing cylinders so the temperature difference across the block would not get too much. Hey as long as it lasts through warranty is all the bean counters want.

Ahhh, gotcha. I hadn’t considered temperature differentials with only half the cylinders firing. I should have thought about that, since I’m an IT professional. Modern day multi-core processors use a balancing act to keep all the cores working to prevent such temperature differentials, and that makes perfect sense. So I agree with you 100%. They should alternate the firing of the cylinders to keep temps more even.

Who says you can’t teach an old dog new tricks. :slight_smile:

My question is how do you really know that was the reason it failed. Was this a mechanic’s theory?

Mechanics pull all kinds of stuff out of their #$$ to explain problems.

As others have said a tuner will allow you to turn off the cylinder deactivation. All the people I know with vehicles that have this feature ( mostly people with newer Dodge Rams )turned it off shortly after having their exhausts done ( straight pipes out the converters), apparently when they switch to 4 or 6 cylinder mode the engines sound ridiculously wimpy.

I apologize in advance for this comment but cannot resist, so here goes:
Tim hats are complementary with straight pipes, so is a big machine gun and a lift kit.

Did you know that they also sell a resistor for the diesel Mass Air flow sensors so you can “make smoke”.

If this is really a major issue, why doesn’t the factory just program it so it doesn’t go into cylinder deactivation mode until the engine’s warmed up?

I’m leaning heavily towards Andrew’s theory. Maybe this mechanic had a bad experience with an 8-6-4 motor in the past?

You should have just bought a 1974 Chevy P/U and restored it…Saved yourself A LOT of trouble. GM went bankrupt. There was a REASON for that. Using 1950’s engine designs and trying to trick them out so they can at least come close to the competition in terms of mileage and performance gets them into a lot of trouble…Disabling cylinders NEVER has worked properly…They just keep trying…

I am sure that the de-activation mode clicks in only after your coolant is at operating temp (210 or so). But regardless of the coolant temp there will be localized cold spots where moisture will accumulate when some cylinders are not firing.
This will get worse if you drive with low loads and short trips. Air cooled engines used to have similar problems with the leading cylinders that were facing the wind.

If you are only going to keep the truck for 200,000 miles and they changed all the lifters, you should be in good shape. I do hope they changed all 16 roller lifters.

Just in: Sorry if you are trying for 300,000 miles.