Home Forums Gear Hunting Trucks and Four-Wheel Drives Suburban 1999 170K miles

or it is downshifting, but just not accelerating....

Don't remember the exact BUT there is a factory setting that causes the above actions

The first moron that looked at mine was going to replace the auto transmission. Took it to a dealer that knew what he was doing, he put it on the scope. Ran a while before it showed.

Changed out the fuel pump , solved.

Same symptoms 6 months later , same problem, faulty pump. Replaced , has had another 200,000 on it ( 1\2 me ,1/2 by next owner). No issue

Went through the exact same thing Lorne about a year ago. Since the fuel pump change it's like a new 5.3. Sure makes a difference doesn't it.

BIG difference!!

After I tried to run it 1/2 full of gas , or better, because I was told it might help. Don't know if it did but it didn't hurt

There is no magic here. If the engine does in fact increase rpm, if it does not downshift,
then it HAS to increase speed. Or something is slipping.

Lack of fuel will decrease power and or cause lack of acceleration. But rpm won't increase. Unless the tranny down shifts to compensate.

The question is, do rpms increase?
For sure, judged by looking at a tach.

Today's experience, and it hasn't always been like this, kick hard on level ground, it downshifts and accelerates great. Do the same thing on a pretty good uphill grade and RPMs go up (about 1000) and seems to downshift but speed doesn't change.

I think a trip to the dealer may be in order to sort through these ideas, which I appreciate very much.

I'm starting to confuse myself. If it weren't for passing on a two lane or climbing La Veta Pass once in awhile I could live with it...but I don't intend to.

Clean air filter?