My buddy has a 99D with 125k on the clock. His truck is having a great deal of trouble climbing hills. What happens is he can never get the truck to go much more than 65mph up and incline on regular roads. What happens is when it is o/d the truck has no acceleration power under a load. If he gives it a little more throttle it will shift down to 3rd gear, hold about 3500rpms and struggle to maintain 65mph. On flat roads and going downhill it runs fine, only under a load going up hill.

I know I have seen a few other posts like this in the past, I just could not find any when I did a search.

 

Try adjusting the Throttle Valve. Over time it can work a little loose and cause you to upshift too early, which sounds like it may be your problem.

 

360Sport:
This can also be a sign of a failing fuel pump. I would think though that he would be getting some indications from the Check Engine light if this were the case.My guess is that the pump output is sufficient to run the motor under a light load, but when on a hill or situation requiring acceleration and high RPM, it just aint "cuttin the mustard"


Le us know how it turns out Don

 

That is something I had not thought of. If it was the fuel pump wouldnt it sputter to some degree since it is not running on an adequate amount of fuel under a load?

He has seen a decrease of gas mileage in the past few months. He has gone from 320 miles to a tank down to 270-280. He has changed the 02 sensors because one failed so he did both of them at the same time. I am wondering if it is the cat, if the pig rich condition could have killed the cat. I am not sure how long it was driven like that but it was a little while (4-6 weeks maybe).

What about the throttle position sensor? I have not messed around with one on a Mopar but could it be failing in a way that it thinks the pedal is at full throttle if it is not? I know on the 3rd gen Camaro's it would not fail in this manner but figured I would throw it out there.

 

Now that you mention the issues with the 02 sensors, I can see where a restricted exhaust or convertor might cause the same symptoms.
I would think though that the CE light would be on b/c thedownstream 02 sensor was not getting proper readings.

About the lack of sputter, what you say does make sense, but we had a 95 Caprice 4.3L V8 at work that would run fine around town, but try to take it on the hwy and kick her down and she would downshift and try to accelerate (no sputter) but could not. As long as you kept your footdown it could not increase the rpm enough to shift back to 3rd or OD. We put 135 K on her in 5 years and I think 4 fuel pumps as well.

IIRC, exhaust restriction can be tested by hooking up a vacuum guage somewhere on the intake and running theengine up to 2-3k rpms. If the exhaust is ok, the vacuum will initally drop and then come back up to somewhat close to where it was at idle, but ifnot the vacuum will drop and stay down as the rpms increase b/c of the restriction.

Don

 

I had a wasted converted in my 97 Ram and never got a CEL. Right now I am on the fence to say yank the converter out if it is not the problem. Although my gut feeling is that it is. Over the weekend I am going to do some more research.

 

If it is your convertor you should address what caused it to go bad, convertors don't just wear out. Something caused it to go bad.

I think a CE light would come on if is is pluged though.

I don't beleive it to be a bad TPS sensor, they are not known for "going bad". They either work or don't work. Same thing with the fuel pump.

I still think you should check both cables on the Transmission. YOu said it goes into third gear and maintains 35oo RPM and stays there! If it won't downshift it probably is in one of the cables.

 

Maybe I was not really that clear with my posting which is entirely possible. When going up an incline he will be in overdrive and the truck will have minimal acceleration power. Then he steps on it a little more and it down shifts to 3rd gear from overdrive and the motor will turn around 3500rpms and not go anymore.

I am totally willing to check the cables. However, can you provide me with some good information as to what needs to be checked and how to do it?

 

my Cat went out with in a couple of days of installing a new one. due to a rich fuel mixture. still trying to fix the problems

 

When was the last time you put a new filter and fluid in the trans?????

I have seen this problem this in the past. Basiclly the motor has to run harder but the trans won't go. You can also have it adjusted if needed.

As for the CAT: You can take it to a muffler shop and have the back pressure tested to see if it is bad. This is usually free and only takes a few minutes. You should not have anymore than about 3 lbs. back pressure and thats pushing it. I have 2 1/2 and run great.