2004 WOT issue

[o4yukonxl]

After struggling with the low RPM performance issues with the Westers PCM, I finally acquired the Autotap software from Tbyrne and logged some runs. To my surprise, the PCM does not allow 2004 trucks to get 100% throttle opening until over 3,000 RPM. No matter what your foot tells the PCM, it overwrites it and gradually opens the throttle as RPM increases.

 

What a screwed up way of controlling an engine. Apparently the GM engineers think that we are not capable of determining when we need full power. That means that when you are towing, and put you foot to the metal, you only get 50% throttle. When I jump on it, I want it all, not what some detroit engineer thinks is best for me. Now I want to trash my throtte body and go back to cables. This is ridiculous. Lyndon is now aware of the problem and working on a fix but it won't be easy since the PCM overwrites the pedal sensor and puts in what it wants the throttle setting to be.

 

I buy a vehicle and expect to get the full use of it, not what GM thinks is best.

[dougsster]

WOW!!!! Thats interesting! I almost bought a used 2003 with like 8000 miles on it, now I wish I had! This big brother crap is only gonna get worse! Im sure hell find a way to tune it out eventually or someone like bryan herter at pcm's for less will find a way to install an 03 pcm like they do for lt1 equipped cars 96 and later that have obd2, just order an obd1 conversion pcm!

 

Thanks for the FYI!

 

Doug

[tdrumm]

Same crap happens with 03s too. d**n drive by wire!

[boomer 33]

That is way out of bounds, they put on precats (finally explains the lower advertised HP and torque numbers), and change the WOT range . What pricks. And then no light under the hood, no lock on the console, no remote lock switch in the rear, weaker hitch, no filter for the interior compartment. Taking content out everywhere and reducing performance for the same or more money.

Bean counters are running GM - into the ground. DCX is waking up to performance, look at the Hemi they are spotlighting and other performance options.

This is my fourth Yukon, you would think they would take the customers wants and needs into consideration. I think I will find another vehicle the next time.

 

I sure hope you guys find a work around for this deal, I bet you will.

[Butch 02 Denali]

I happened to be talking to Lyndon today and he says he will have a fix for the 04 throttle open delay by the end of the week. This delay is NOT in the 2003 or earlier trucks, only the 2004 8.1's.

Seems crazy GM would do that, you'd think the crappy torque management would be enough!!!

 

BTW..you can use a 03 PCM in an 04 truck, but when you flash it with the correct VIN program for the of truck you get the throttle delay. The problem is in the program code, not in the PCM hardware.

 

Butch 02 Sierra Denali

[99Silver6.0]

Gotta love the ETB and torque managment!!

[pritch55]

I myself just sent back my Wester tune because of poor performance in the low RPM range. I believe that this will affect more than just the 8.1 I don't have an auto tap but there was no difference from stock to the Wester in first gear up to 3000 rpm.

 

Can anyone who has a 2004 other than the 8.1 and has access to an autotap please confirm that this only affect the 8.1?

 

 

Thanks,

-Brandon

[dougsster]

I just had an interesting though....Does anyone have any stock dyno #'s and do they line up with GM's advertised torque & hp rating from idle to 3k? The chart I found shows the torque at 400 as low as 1k and up to 200hp at 2k and about 275hp at 3k.

 

It reminds of a mustang cobra a few years ago that manufacturing flaws in the cylinder heads and crushed flat exhaust that was producing #'s way lower than claimed! I beleive a class action settled that in a hurry and most those cars heads and exhaust and finally produced the #'s ford claimed. Not to say the 8.1 is a slouch....look at the results from an air intake and protype westers tune on 04yukonxl....Im just saying it had better be making what they claim. I can hardly wait to see how this turns out!

 

Doug

[boomer 33]

Butch, is Lyndon going to call you or Glenn when he comes up with the fix? I need to get mine burned again when the fix is in. This could be good.

[Butch 02 Denali]

Butch, is Lyndon going to call you or Glenn when he comes up with the fix? I need to get mine burned again when the fix is in. This could be good.

Glenn's been the guiney pig (no offence Glenn!) so far with this, let him get the cure first, and he can check it with his Autotap and make sure it's 100%. I'm sure he'll report his results here!

 

Butch 02 Sierra Denali

[robsawatsky]

Before everyone gets too worked up about this delayed throttle opening, I think it should be determined exactly how this effects engine performance. I did some digging and couldn't find a technical description of what this delay is supposed to accomplish other than 1 place where it did state that it allowed for better control of the air/fuel ratio. Since the throttle opening is now decoupled from the accelerator pedal position, I'm not sure how fuel delivery is calculated and what effect it all has on power. Maybe marginal?

[Butch 02 Denali]

Who knows Rob, maybe it won't have a big effect on power, maybe just faster throttle response? We'll find out when Glenn gets this update and tests it out! Now if one of you with an 04 with an 8.1 wanted to take a ride up to Lyndon's to spend a couple of days on the dyno......

 

Butch 02 Sierra Denali

[tdrumm]

Check out this link from ls1tech.com

[Chevyfreek]

This is very interesting news. The first I have heard of this throttle delay. GM has a lot of issues they need to address for sure. The list just keeps getting longer...

[whodat187]

Hey tdrumm what exactly do you mean drive by wire in the 03's What are any issues like those or any other with the 03's I mean i have the 4.8 ecsb so any power i can find is helpful I just alway sliek to hear others opinions!!!!!!!!!!!!