Stumbling and hesitating 6.0

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strad

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9/2004 Escalade ESV. 220k miles.

Hesitates and stumbles badly, going from a standing start, usually after idling (and heat soaking) at a light for a few minutes.

It does not do it when the engine has been sitting all night. Engine must be fully up to operating temperature, and been there for awhile, and ambient temp is higher than 110.
It does not do it (much) if the ambient temperature is less than 110, even if fully warmed up. If it's 95 or less, it's fully happy and doesn't do it at all.

There are no codes stored that I can read with my basic OBDII scanner.

Since I have a Suburban (5.3) built the same month, and since it uses the same MAF, I swapped its known good MAF unit into the escalade. That made no difference.

So I know it's temperature related, and I would assume that a scan tool that displays live data would be helpful (lol) but I don't have that. Any ideas?
 

Big Mama

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I hope you don’t get too many days over 110.heres a few basics you may have already checked. How are the fans operating? How is your battery? Does the engine temp rise? Air filter box and tube ok with no cracks? Could it be a trans issue? Temp ok there?
 
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strad

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I hope you don’t get too many days over 110.heres a few basics you may have already checked. How are the fans operating? How is your battery? Does the engine temp rise? Air filter box and tube ok with no cracks? Could it be a trans issue? Temp ok there?

Fans run ok at low speed. I am not sure if they kick to high speed or not. I know the suburban's do, and I know what that sounds like, but not sure how to compare by sound. . .

It will indicate slighly over 210, but a check with an IR gun indicates 200-205 at water pump and at upper radiator hose, when gauge is reading higher. Normally the gauge reads slightly under 210, and I would have to say the hesitation issue exhibits more when gauge is at 210 or slightly above.

Battery is good. Air filter box seems ok, and tubing appears to have no cracks (no unmetered air). Trans temp is similar to coolant temp (this truck has an oil cooler and a trans cooler installed from factory). Fluid in trans is about 7 months old, and the trans shop that changed it didn't say anything untoward about trans pan contents when they changed it. They did make a negative comment about the front differential fluid they took out, so I know they were paying attention. But that's another issue.
 

BG1988

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MAF or MAP sensors are weak those can cause it to stumble
 

Big Mama

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I believe your fans have 2 speeds and the MAP may not throw a code just yet. I think the parts chain stores will let you “borrow “ a scan tool that can read live data. If not maybe someone on here is in your area. I bought mine from hobo freight the ZR13 as we have about 7 car makes in the family it was $179 and reads everything I’ve been happy with it
 
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strad

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I believe your fans have 2 speeds and the MAP may not throw a code just yet. I think the parts chain stores will let you “borrow “ a scan tool that can read live data. If not maybe someone on here is in your area. I bought mine from hobo freight the ZR13 as we have about 7 car makes in the family it was $179 and reads everything I’ve been happy with it

Thanks I may be at the point of checking that out. Yes I know the fans on the suburban are two speeds. I would assume the Escalade is also since it’s very similar. And I’ll bet there is a high speed fan issue with the Escalade although I need to learn more how that would cause my stumbling issue.

As for MAP, I bought a new one and installed. I don’t think that is the issue. What I haven’t done yet is run the known good MAF from the suburban with the new MAP sensor on the Escalade.
 

Big Mama

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Makes sense. The fan speed shouldn’t cause stumbling but best to cover your bases at your temp. It would be unusual for MAF and MAP to go bad together but one may have been weak for a while. Good idea about borrowing a more detailed scan tool
 
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