[lonestar]

lately, when I brake for a traffic light or sign, my '07 Colorado LT w/I4 engine shudders and acts like it is going to quit. My only mod to it is a K&N replacement air filter (spend most of my money on my motorcycle)! Can anyone direct me to a possible explanation and fix?

 

[Skizzo]

Manual or auto? Also, I will make the obligatory clean your throttle body and MAF suggestion.

I have seen a few people on here say there is a known tuning issue from GM on here that causes that and a dealership can flash your computer but I am not sure. However, it is a very common problem on here to have a low idle upon braking/coasting and what almost always seems to fix it is cleaning the throttle body and MAF.

 

[08Canyon]

Here is a link to how to clean your throttle body. There is more in the thread, but cleaning the throttle body is a good place to start.

Make sure you go to the store first to pick up Throttle Body Spray Cleaner.
http://www.355nation.net/forum/how-...w-change-spark-plugs-clean-throttle-body.html

Is there any relationship the the erratic idle and your replacement air filter? How long ago was the filter installed? When was the last time you oiled the filter?

 

[FrEaK_aCcIdEnT]

Check your idler pulley assembly as well.

 

[GM Customer Service]

Hey there lonestar,

I understand that you are looking to fix this issue yourself. I see that you have had many forums provide you with possible fixes to your issue. I cannot provide you any do-it-yourself type of advice, but I would be happy to look into this concern for you. Feel free to contact me via private message any time!

Jennifer T.
GM Customer Care

 

[lonestar]

I use a can of Seafoam every so often to clean the throttle body, but this doesn;t seem to help the problem. I have checked the air filter and was surprised at the low level of dirt I found on it, so I don't think that that is the problem. Transmission is automatic. I really haven't done much work on this truck and didn't do any on its predicessor, a '04 w/manual tranny. I just kept taking it to my dealer, but now its paid off, so I plan on doing more with the truck (when I'm not working on/riding my motorcycle). I'm ashamed to admit that I didn't even know how to access the plugs-prior to my first Colorado, I did all the work on my '91 Isuzu SpaceCab! I have the factory manuals for the '04 (figured they hadn't changed much in three years-do you recommend the Clymer's?

 

[Goros]

there is a TSB for a low idle stumble out there, after you clean the TB and seafoam the head get both your computers flashed to the latest releases

 

[08Canyon]

I use a can of Seafoam every so often to clean the throttle body, but this doesn;t seem to help the problem. I have checked the air filter and was surprised at the low level of dirt I found on it, so I don't think that that is the problem. Transmission is automatic. I really haven't done much work on this truck and didn't do any on its predicessor, a '04 w/manual tranny. I just kept taking it to my dealer, but now its paid off, so I plan on doing more with the truck (when I'm not working on/riding my motorcycle). I'm ashamed to admit that I didn't even know how to access the plugs-prior to my first Colorado, I did all the work on my '91 Isuzu SpaceCab! I have the factory manuals for the '04 (figured they hadn't changed much in three years-do you recommend the Clymer's?

Can you explain what you mean by "using a can of Seafoam to clean the throttle body"?

 

[lonestar]

Add a can of Seafoam to a fresh tank of gas-helps clean the injectors and, as I thought the TB-am I mistaken? The stealership asks a pretty heafty sum to 'clean the fuel system/injectors'.

 

[08Canyon]

I know there are dosing suggestions on the can. I don't recall the dose rate to fuel ratio. But I was in fear that you used a full can in the intake.

Seafoam in your fuel will not clean the throttle body. A throttle body is cleaned manually by removing it from the intake.

Mixed with fuel it cleans the fuel system. It is carried from the tank, through the fuel lines and through the injectors. That's it. Air and fuel are separate until it's mixed in the cylinder.

Administered to the intake, it cleans the upper intake system.

The 3 different things mentioned here are:
-Fuel system cleaning
-Throttle body cleaning
-Intake cleaning

 

[lonestar]

Well, for the first time on a Colorado, I decided to do the job myself. Got the MAF and Throttle body sprays, and viewed the howto listed above, and went to work on it. I really couldn't see that spraying the MAF did any good, but the t/b?-Damn that thing was nasty. Couldn't find any of my used toothbrushes at the time, so I used one of those flux brushes. Ended up using one of those blue shop towels for the most part. I was amazed at what a difference cleaning both items did to the actual running of the truck. It's an '07 with @65.5K on it-first vehicle I've bought new that I exceeded the time of the warranty vs. the mileage (must be because of all the miles I've put on my motorcycles that I bought since then-650 [wrecked after3 yrs] 950 [traded after four years]and two different 1700s [one wrecked after 48 DAYS]- all Yamaha [Star}s. Put over 15k on the latest in 1 year)!

 

[08Canyon]

A flux brush? Are they course?

It's over now...got it. But all you need to do is spray it and wipe it with a shop towel. I supposed a super fine brush (maybe I don't remember how soft a brush used to apply flux is) can be helpful to clean around the butterfly pivot.

Spraying the MAF Sensor (internally on the wire filament) will wash away any residu that may have built up on the fine wire. Nothing visual.

The design of this system dirties up the throttle body and seems to be routine maintenance on our vehicles, but is not common or many other vehicles, other GM engines included.

 

[lonestar]

Is there any frequency in doing this maintenance?

 

[Goros]

At least 1x per year.