Throttle cutting back
 

Hi,

I have a '97 Cummins w/ auto trans/ 125k on the odo

It shifts fine - but going up a hill my throttle cuts back on occasion and is unresponsive to more pedal- you can put it to the floor with no effect. Seems to be getting progressively worse.

No check engine light on. ran a scan and no fault codes come up. Only clue I have found is TPS voltage with key on/engine off is 0.70 and minimum should be 0.76

does this sound like a faulty TPS ? Anybody have any clues?

thanks!

it cuts out around 2200 - 2400 rpm? do you have stock gov springs?

yes - I would say that is about where it cuts out.

It does maintain higher rpms when I first get rolling. It just seems to be after a shift and usually going up hill. Otherwise it has plenty of power.

Everything is stock and pretty much as I got it off the shelf. Original owner here and it has needed nothing other than filters and a couple of fuel lines replaced a year or 2 ago.
thanks for the response-

Keith

you should check the TPS to make sure you have the right voltage. A set of gov springs will give you some extra power above the 2400 rpm wall of the stock springs

you can knock the metal tabs out and drill those mounting holes larger, then rotate the tps counter clockwise for a increase in voltage. sounds like your gov. springs to me as 94 12valve said.

Maybe its my poor reasoning, but if the truck is able to hold the higher rpm under certain conditions , wouldn't that indicate something other than the governor springs? I was thinking more along the electronic controls direction.

admittedly this is pretty much out of my field and am open and thankful for all ideas.

The problem with the stock governor springs is that they restrict fuel after 2200. So, the gov springs do two things. Defuel after 2200, and keep you from going over 2900.

I doubt anyone changes the springs so they can get more RPM's. These engines don't really benefit any by going over 3000. They mainly do it to remove the defueling effect of after the 2200 mark.

Which in your case... would allow you to accelerate when going uphill well into the 3000 RPM, mark; instead of only 2200.

However, seems that changing the spring gives you a sensitive pedal more often than not (more so for with the 4K kit). Which is one of the reason why I haven't done it to my truck (even though I already bought the kit some time ago). Then I do live in a area that has no hills. Plus, my Dad talks me out of it every time, I bring it up... And I'm too C.S. to do it by myself.

Oh, and the only difference between the 4K kit and the 3K kit is that the 4K kit gives you the inner springs to change out. So, if you don't install the inner springs on a 4K kit.... it becomes a 3K kit. At least that's what the instructions tell you on the Pacbrake brand.

I disagree with the point made in bold

Defueling- yeah that sounds like what is happening - like the pedal is coming up off the floor.

Sounds like I have 2 directions to look in which is good. thanks for the input!

When your Gov spring is defueling it shouldnt have any effect on your throttle pedal, if your pedal is coming up when you accelerate up hill I'd check things like engine, trans, and cab mounts :c:

I ordered the TPS and hopefully that will be the fix-I don't know anything about governor spring replacement.

Any other votes on what the problem might be?

i really do not think it is your tps. when you got the 0.76 was that at WOT ( wide open throttle). did you try adjusting it before buying a new one? tps controls 4th gear and o/d as well as converter lock up. i really think you have a fuel problem:humm:

Thanks for the response.. I had ruled out a fuel problem. I changed the filter and it seems to have plenty of power and fuel delivery until the point where it cuts off and rpms drop.

the .76 number is what it should read at engine off/ key on but the reading I have at that is .70 leading to the idea that the tps has atleast some issue indicated.

did you check it with the key on and throttle all the way forward. you can knock out the metal mounting pins on the tps and rotate it counter clockwise for more voltage. if that does not work you can drill those holes out to rotate the tps even more for increase in voltage. i did all this but mine was shot. a bad tps will constantly be hunting for gears and lock and unlock the converter. i would try this before spending the money on that spendy piece of plastic as your issues don't seem to be tps related from the sounds of it. i really think it is your gov. springs!:humm:

ok, I will try that before installing the new tps . I went ahead and ordered it from advance auto since I had a $40 off coupon. they usually have good promotions plus their return policy is really good.

and thx for the vote on it being gov springs. I will be looking into replacing them.

I talked to Mark at tstproducts.com who said he had never heard of governor springs wearing out. He suggested I look at the overflow valve which is a common cause of low power and/or other fuel problems.

I took the OFV out and it looked fine, but before reassembly I stretched the spring as he recommended and the truck now runs like new - even idles much better. I will be replacing the unit with a new one. I wanted give an update for anybody having a similar problem in the future. thx to all

that is good info thanks.gov. springs don't wear out they just lose tension. glad you got it resolved:jump: