It's been a while since one of my trucks has had me so stumped so I hope someone can come up with something I have missed.

Truck is a 2000 S-10 4.3 vin W 240k miles

I have noticed over the last few months that more and more often my truck is lacking power badly when going uphill. It feels almost as if I am taking my foot off the gas when going up any kind of hill.

imagine an old 1.something liter economy car loaded with people trying to climb a mountain road and you will know what it feels like in my truck lately on a small hill.

The only way to get around the problem and maintain speed on steeper hills is to essentially floor it. After a couple seconds with the pedal to the floor it will finally start to respond with enough power to get back up to speed. But still not responding with the amount of power you would expect.
Still plenty of power when not on a hill though. Even with the high miles you can still squeal the tires on dry pavement just as well as when she was new.


There are no engine codes
A compression test shows that all 6 cylinders are still within specs given in the chiltons manual.
Has had new distributer installed along with plugs, wires, and cap, rotor within the last 6 months when I replaced upper and lower intake manifold gaskets.
EGR is about a year old and nice and clean still.
IAC valve is under 1 year old, tests good and is nice and clean
catalytic converter is about 1 year old and no rattles
TPS tests perfect
MAF is new within the last 2 years. also clean
O2 sensors were both replaced with the cat.
Spider assembly was replaced with the new updated one 2 years ago.
Fuel pump is 3 years old and pressure is within spec including when driving uphill. Reading is at 60 for pump prime 59 during cranking, 62 at idle, and 60-64 while driving including when the problem occurs. leak down test shows within spec.
Fuel filter replaced a week ago.
No apparent vacuum leaks that I can find
No loss of coolant
No leaking or loss of any fluids at all.
Transmission fluid is clean and at the proper level, not burnt and with no indications of a slipping transmission


I am starting to run out of ideas on this one. Aside from the massive power loss going uphill she seems to run perfectly.

Any ideas?

 

Cat good. How about the muffler? Are you getting good pressure out of your exhaust?

 

Yes, the cat is good as is the entire exhaust which I replaced front to back about a year ago including a new muffler. The exhaust flow is good with plenty of pressure.

 

A couple of more things I would check.
1) Restricted intake. How's the air filter? Another thing that happened to mine was I have a corrugated hose on the intake (1994) and when you needed power and stepped on it the hose would collapse and restrict the intake air. Took off hose and it ran like a champ. Put on new one of course. Don't know your setup but you might see if something like that is a possibility.
2) When I cleaned my EGR, I noticed that the port in the intake manifold was completely plugged up with carbon. I see where you cleaned the EGR valve. How about the port?
3) PCV valve just because. These cheap little parts have caused power problems since their inception.
4) Looked in the book for possibilities and you've conered most of them. A plugged injector is mentioned but takes a tester to check. Maybe someone else has a way to do this. I don't know. It also mentions the Torque Converter Clutch. Of you have an automatic I think with your foot on the gas going kinda slow (maybe 25 mph) if you just slightly push on the brake pedal you can hear it release (slight RPM rise). At least this is how you check it in a 700. I haven't tried it in the 4L60-E but you might give it a shot.

 

The air filter was changed along with the oil last weekend so I doubt that is it. I will check the short corrugated intake hose between the MAF and the intake though. That is something I have never considered.

When I replaced the intake gaskets I polished the entire intake back to shiny metal again including the EGR port. But, I suppose it wouldn't hurt to pop it off again and take a look.

I also changed the PCV valve along with the oil last weekend. It didn't need it but I change them along with the air filter as routine maintenance since they are only about $3.

I'll look into the TCC for my model. Usually any torque converter issues come with odd RPM happenings that I haven't noticed on my truck. I will look into it further just the same though.

Thanks for the ideas. If anyone has any more please jump in.

 

Update
Gimpy Blazer, Thanks for the idea of checking for a restriction in the intake ducting.

When the engine got warm the corrugated hose in the intake ducting would collapse a bit when I revved the engine. I imagine the collapsing would be worse if the engine was truly under load such as going up a hill or hauling something.

A quick swap of the intake hose with my 01 blazer and my pickup is taking hills like a champ once again. Now I just have to locate a replacement for the 01.

Thanks again for the idea, I was getting quite frustrated with not being able to find the cause of the problem.

 

I don't know if they sell one for an 01 but mine came from O'Reilly. It costs $8.49. I know this is for my 94 but they might have one for yours too. It's a Dorman part. Here's what collapsed on mine.
http://www.oreillyauto.com/site/c/se...zer&vi=1060580

 

I assume you have fixed your problem by now, but as I had the same issue and could not find the proper answer on this forum, so let me post it here:
while many point towards the fuel pump or the MAF (which can have similar symptoms), in my case the problem was an air leak at the upper intake manifold.
When you revved the engine from the engine compartment, it sounded a bit like a hole in the exhaust system at first.
It became so bad that in the end I could only go 10-20 mph if there was the slightest incline, because as soon as I gave more that 1/3 gas all the air went through the leak, the MAF threw an error code and the engine choked (but never died).