hesitation

[feb]

I have a 2003 trailblazer with the inline 6. Great car, power and comfort.I have a slight hesitation when I crank up the car, put it in drive and take off. After that first hesitation, it does not do it again until I turn the engine off, crank it back up and take off. First, the dealership reprogramed the computer, and the next time they cleaned the throttle body saying there was carbon buildup. I have 14,000 miles on it. It works better now but there is still a slight hesitation at times. Anybody else having this problem and ofcourse, the cure?

Frank

[nodemgr]

I have noticed this hesitation and I figured it was simply programming to reduce strain on the drivetrain like the torque management programming. I see the issue when I put the car in drive and press on the gas before the transmission fully switches to drive. If you wait a few seconds after putting the vehicle in drive do you still have the hesitation?

By the way, the torque management is annoying. Anyone know of aftermarket programming to disable the torque management?

[hefdog]

I'll see if I can find some info on this but be careful about overiding the torque management. GM had to lower the torque on take off so that it would not twist the transfer case housing and cause damage. Any time you increase torque input you are going to eventually find the weakest link. Which in this case is the drive line particularly the alluminum transfer case housing. If you beef that up then you'll find the next. GM gets this vehicle moving then it brings on higher torque.

[hefdog]

There have been calibration updates to help with Hessitation but if the dealer has already updated the calibration then make sure you are using 87 octane. It is more volatile so in cold weather it lights off better and reduces hessitation. Also if you have dealer run top engine cleaner through engine to remove any carbon on the valves and pistons this will help. Carbon is like a spong when you first start an engine and it robbs some of the fuel. Once it is fuel soaked you don't notice it anymore until it dries out again then on the next start it soaks up fuel again. It doesn't take much to do this since we are talking about very fine mixtures. So it does not mean your low milage vehicle is all carboned up. It doesn't take much these days to effect cold driveability due to trying to lower emissions. After trying these things or if this has already been done then your probably are looking at this being the nature of this vehicle. They are very "cold blooded" by nature.
Take care!

[feb]

Thanks for the info. I did notice that in cool weather the hesitation is very slight. When the weather is muggy, as it is here in louisiana, I feel it more. I'm using exxon regular and also chevron regular. Should I use the chevron additive every so often?

Again, Thanks,

Frank B.

[hefdog]

Probably a lot of opinions on fuels and cleaners. Personally I use a high grade fuel (high octain) like Mobil or shell when I take a long trip. I run one tank through on the trip then I go back to normal 87 octain. Different engines are also different in the amount of carbon build up and the effects it has on the engine. Some people have a routine such as running highgrade fuel every fifth tank or so. It is known that some fuels do clean better then others so when you find one known to help then use it occasionally but if it is winter time understand the starting and cold hessitation may be slightly effected.

[hefdog]

I should probably add that decarboning an engine with top engine cleaner has become or is becoming a routine just like changing oil except at higher mileage intervals. Most would suggest this procedure on engines like yours every 20,000 miles.

[nodemgr]

Originally Posted by hefdog

I'll see if I can find some info on this but be careful about overiding the torque management. GM had to lower the torque on take off so that it would not twist the transfer case housing and cause damage. Any time you increase torque input you are going to eventually find the weakest link. Which in this case is the drive line particularly the alluminum transfer case housing. If you beef that up then you'll find the next. GM gets this vehicle moving then it brings on higher torque.

Thanks for the info. Does this apply to 2WD vehicles also? I didn't think my 2WD TB has a transfer case.

[hefdog]

Same principle applies although if you have the same calibration as a 4x4 you may be able to get away with a little more torque. But you may find the next weakest link.
In general automotive companies try to give you all the hoursepower and torque they can without compromising parts. They want there parts to last awhile so they don't have high warranty cost. Example: people are turning up the horse power on duramax diesels in the chevy trucks. But many are now burning up clutch packs in the transmission pre-maturely.
Now when it comes to just overriding emmision components, that's where it won't hurt the vehicle just the environment.
If you are referring to the hessitation yes, it will be the same issue. That is not a full throttle start that is just a normal take off and they both will be tuned the same under normal condition.

[sunspeck]

The service techs at my local dealer told me that the hesitation was due to the onboard computer being cold. That as the car/computer warms up, the car won't hesitate and jump. I'd love for someone to explain why that happens when it's 90 degrees outside. It must be too cold for the hunk of junk, eh? It hesitates and jumps, squeeling the tires! I personally hate the 2003 trailblazer LT EXT!

[feb]

Acutally I love my 2003 tb. It is only that inital hesitation I hate. I get about 22 1/2 to 23 mpg on the highway. I don't think the service dept. know how to stop the hesitation. I never heard of the computer being cold as the cause. Sounds a bit fishy.

[hefdog]

Cold computer is a terrible line of reasoning unless you had losse wire connections and then you would probably have codes and other issues too. These computers are tested for proper funtion in extreme cold such as below -60 deg F. So the only way I will buy that is to take the computer out. Warm it up. put it back into your cold vehicle as see if the hess is gone. Then take it out. cool it off. Put it back in to a cold vehicle again and see if it returns. this should be doen to make sure it was not just a loose connection and not the computer. I am not buying that story. Most vehicles hessitate at moderate temperatures on start up. Not when it is real cold or warm but about between 50 deg and 80 deg on cold start. And it can be seasonal due to the Winter and Summer blends of fuel. So if it is the computer then why does it not hess when it is real cold (20 deg)? Take care!