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Discussion Starter #1
I have an '06 Colorado Crew Cab with 120k miles on it. I have neglected it for quite a while since there was nothing 'wrong' with it. That said, about 2 months ago, I got the CEL for a stuck thermostat. I finally had time to get it into the shop last week and have it switched out. Since the switch was done, it has started to have a slight 'power drop' or 'studder' when I am driving at freeway speeds, lighter throttle and lower RPM's (55-60 MPH at 1500 RPM's)... Also the mileage has dropped from around 22MPG down to about 16MPG...

The only thing I found under the hood was that a plastic clip that has four wires leading in to the engine - it's right on the front of the motor - cracked and was loose, but I zip tied it back on and made sure none of the wires were broken.

I know I need to change out my air filter and probably need to change my plugs and wires soon. Has anyone had a similar situation to this? Could it be the coil?

My next stop is probably going to be the dealership to have them check it out, but they said without having some kind of code to run, they may not be able to find the exact cause.
 

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any excessive squealing from the belts or pulleys?

the cold weather will cost you mileage also.

I'd do a full tune up anyway, our trucks are due for plugs at 100k miles (50-75k if platinums instead of iridiums) and some other stuff, head cleaning, tb cleaning, etc.

You don't have plug wires. We have coil on plug, so no need to worry about that.

Here is what my 100k and 200k service looked like on my truck

Oil & Oil Filter
Air Filter
Exhaust Camshaft Actuator Solenoid
Fuel Pressure Regulator (not on 2006)
Fuel Filter (not on 2006)
Transmission Filter & Fluid
Radiator Flush & Fill
Differentials Drained & Filled
Transfer Case Drained & Filled
Spark Plugs (denso ITV16's) w/supersparkz spring delete
Shocks (Rancho RS5000's)
Throttle Body Cleaning
Seafoamed head
Cleaned MAF Sensor
Replaced MAP Sensor

From experience I would add:

Flush and Refill Brakes
Flush and Refill Power Steering
 

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Discussion Starter #3 (Edited)
Thanks for the info,

I'll do the air filter and the plugs next. I'll take a stab at cleaning the MAF and the Throttle Body after that.

Oil and Oil Filter was just done along with a fuel system flush (was hoping it would help the issue)
Transmission had a new front seal put on about 6 months ago and was flushed at the same time

Other than that, I'm worried that it could be something bigger - though it sure doesn't seem like it.
 

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Buy a spray can of maf cleaner and clean the maf also run a can of sea in the he tank next fill up. I'm not certain but it may be starving for fuel and you need to rule that out. Change the fuel filter after that I'd put the gage on the rail and look at that.
 

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Discussion Starter #7
Well, the bad news is the stutter is now getting worse. I did it at idle today...

I'll start the cleaning cycle as soon as I can. Does the fact that it is starting to get worse give anyone any additional insights?
 

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Step 1 and the easiest in my opinion. Clean the throttle body.

Remove the intake tube and resonator box (large rectangle plastic piece on top of the engine).

There are 4 small bolts that hold the throttle body to the intake manifold. As well as one electrical connection and some other vent thingy. Be careful not to break the tap from the electrical connector.

Once the throttle body is in your hand, spray it with throttle body cleaner and wipe with a clean rag. Repeat until you can't get it any more clean. Do not use an abrasive rag or anything to clean it. Scratching the throttle body (throat) is bad. The backside of the butterfly (circle plate that moves) is what gets most dirty. You can't see that while mounted to the intake.
Wipe the mating surfaces clean and make sure the O-Ring is clean and in the groove. Reinstall.

The MAF Sensor is super simple. Remove two small screws. Spray it with MAF Sensor cleaner. Reinstall. Take note of how it is installed once you pull it out. There is a slot in the housing. Through that slot there is a filament that is visible (similar to a light bulb). Spray that with the cleaner. Don't try to use a screwdriver or anything else to scrape it clean. Just spray, and reinstall.

Plugs can be next on your list, and are likely due if you have 120,000 miles. At idle, the TB is usually one of the first things causing a slight misfire or low idle.

The electrodes may be burning up on the plugs which could explain the rapid deterioration of the idle. Hard to say. Should you elect to change plugs with a factory replacement iridium plug, do not gap them.
 

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I had these exact same symptoms after attempting to get the truck started in -30 or so temps. We had taken the plugs out and I'm sure we were leaning all over the block troubleshooting. In the end, had to replace 3x coil packs.


Sent from AutoGuide.com App
 

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Step 1 and the easiest in my opinion. Clean the throttle body.

Remove the intake tube and resonator box (large rectangle plastic piece on top of the engine).

There are 4 small bolts that hold the throttle body to the intake manifold. As well as one electrical connection and some other vent thingy. Be careful not to break the tap from the electrical connector.

Once the throttle body is in your hand, spray it with throttle body cleaner and wipe with a clean rag. Repeat until you can't get it any more clean. Do not use an abrasive rag or anything to clean it. Scratching the throttle body (throat) is bad. The backside of the butterfly (circle plate that moves) is what gets most dirty. You can't see that while mounted to the intake.
Wipe the mating surfaces clean and make sure the O-Ring is clean and in the groove. Reinstall.

The MAF Sensor is super simple. Remove two small screws. Spray it with MAF Sensor cleaner. Reinstall. Take note of how it is installed once you pull it out. There is a slot in the housing. Through that slot there is a filament that is visible (similar to a light bulb). Spray that with the cleaner. Don't try to use a screwdriver or anything else to scrape it clean. Just spray, and reinstall.

Plugs can be next on your list, and are likely due if you have 120,000 miles. At idle, the TB is usually one of the first things causing a slight misfire or low idle.

The electrodes may be burning up on the plugs which could explain the rapid deterioration of the idle. Hard to say. Should you elect to change plugs with a factory replacement iridium plug, do not gap them.
As the last line here... Factory plugs.
 

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Discussion Starter #14
Did the plugs and it helped a ton, running much smoother... I still feel like it's not at full strength and mileage is still down a bit. I'll try the intake cleaning and the MAF next.
 
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