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DB2 Throttle Pedal Resistance

dbrannon79

dbrannon79

I'm getting there!
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On my 93 I have been letting my youngest son drive it around to get some practice on larger vehicles. one thing he said was how much stiffer the throttle pedal is compared to all the other vehicles we have including my 95 truck. when I first got it on the road I too noticed right away how stiff the pedal was but just dealt with it.

I am curious hearing from others who have driven both trucks with DB2's and DS4's along with other cable driven vehicles to see if it's just me or there is something I need to tend to on this rig.

I did attempt to pull the cruise cable off along with removing the double spring from the IP just to see if that made any difference. the cruise cable didn't seem to change anything but by unclipping the double spring on the IP the pedal was much easier to press but did not return, (that was a given as it needs a spring)

looking at the angle of how the throttle cable goes through the bracket and pulls on the lever on the IP it's at what I call a steep angle meaning that where it's pulling from it looks to me that it would take more force than if it were at a different angle pulling.

I also know that the throttle shaft that is on this DB2 is one for a hummer not for a truck as it has the provisions for the two wire TPS for military applications. not sure if that makes a difference. I do have a throttle shaft made for the truck version of this IP and the side where the cables attach are different. I have never gotten myself enough courage to attempt swapping them out. Afraid I would get stuck with an IP I couldn't get back together LOL.

If I were able to swap out the throttle shaft, I could eliminate the cable driven TPS and use the three wire GM one for the trans controller too.

I know @Will L. has experience with the military versions of the DB2's. this one even had the 24v shutoff solenoid until I swapped the top cover out.

Whats everyone's experience with how much resistance or how hard the throttle pedal should feel on these trucks? for my 17 year old driving it, he tells me he feels like he's flooring it compared to others, he cant use his toes to press the pedal and needs to almost full foot it like the brake pedal. I will admit that it will tire my foot out driving long distances without the cruise control! Thank goodness that does work LOL.
 
dbrannon79 said:
On my 93 I have been letting my youngest son drive it around to get some practice on larger vehicles. one thing he said was how much stiffer the throttle pedal is compared to all the other vehicles we have including my 95 truck.
Click to expand...

Don't Do Drugs, Son! All our other "Drive By Wire" vehicles are NUMB. Some Drugs make you NUMB just like the lack of any feel on electronic throttles.

This here 1993 only lacks "Feel" from a shift cable going to the transmission so you can't feel the edge of when it's going to downshift. You get to feel the throttle input and know when it's at 100%. No 75% pedal travel for 100% and 25% travel of NOTHING past 100% throttle like the electronic versions.

Cable resistance, spring, DB2, resistance are all felt in the pedal. So is the unique momentary "grunt" sound when you slap the throttle to the floor.

Please tell me you have driven a 4 barrel with mechanical secondaries you can feel open by the throttle? Aside of leaning ya back in the seat...

As long as the cables are in good shape, moving well, and the pedal is also moving free ... welcome to "Old School" before Electronic NUMB!
 
You could disconnect the throttle cable at the pump to ensure that the cable moves freely through it's shielding. Other than that, I think you answered your own question with the shaft difference and pull angle.
Or, you could leave it and that would keep your son from straying too far from home, LOL.
 
So- you disconnect the cable from the ip shaft- pull out on the cable. Then go step on the pedal. You should feel almost nothing.
If it is stiff- the cable needs cleaned with brake cleaner then lubed with graphite.

If that doesn’t clear it up, the cable probably needs replaced.

The ip with the springs removed should have very little resistance.

I’ve no input as to swapping those ip parts.
 
I will disconnect it from the IP later tonight and see how free it is. I didn't feel much resistance when I pulled the springs off so I assume it's all about the pull angle with the Humvee throttle shaft. the bracket makes the cable stick straight up from the engine but then when the hood is closed the cable is also pushed over by the hood as well as the cruise cable too. I will clean and lube the cable anyway, I'm sure it needs it.


Yes I have driven several 4bbl old school cars and trucks in my day but don't recall them being as stiff as this one. Once I get it disconnected and re-lubed I will know for sure it's just me and my infinite wisdom that is the problem HAHA
 
Well I didn't get a chance to check or lube the cable tonight. I will try again tomorrow, the wife has other plans for me LOL on top of my older son wanted help replacing the screen on his iphone!
 
Well this evening I got a chance to check the throttle cable. it moves freely and seems perfectly fine. got that out of the way.

I also studied how it was connected to the IP and looked at the 6.2 in relation to the angle, that again was the same. Nothing to see there.

Then I had the intuition to look at the pedal assembly.... well while I was looking it over and pressing it with my hand I quickly realized that the lower piece of the pedal hits the floorboard (carpet) with just a slight push, then to get anymore pedal movement you have to ether press really hard or move your hand (normally your foot) further up to the center of the pedal to get movement which also in turn needs more pressure applied due to the cable resistance but more importantly the bottom of the pedal digs into the floor.

This caused me to go look at the other truck.... I then found out that the pedal position and angle was a little higher from the floor and both the brake and accelerator pedals looked to have the same slant as I eyeballed them. on the 93 the accelerator pedal was more in a up/down angle than the brake pedal also closer to the floor.

Now I know that comparing theses two trucks is not a good comparison since one is drive by wire and the other is cable driven so I took my comparison with a grain of salt. I took some photos standing in the same location outside the door as well as trying to line up the phone camera with the brake pedal to get a better look. Here is what I came up with... both pedals felt the same as far as resistance when pressing in the center with my hand, both pedals also pivot on the steel and are spring loaded. I am assuming the plastic part of the pedal on the 93 has some wear on it where the steel stop is as it springs forward. first I tried wedging a loose coin in between the plastic and the steel stop on the area that rotated. this seemed to help lift the pedal further up from the floor as well as put it's angle more in line with the brake pedal, but I could see the plastic pedal flexing some as I pressed on the bottom and I didn't want it to break.

I ended up using a couple of plastic zip-ties up at the top of the plastic of the pedal strung back to the steel rod underneath making the pedal tilt back the same as it did with using the coin. I only tilted it back maybe 1/2" and it was looking about the same as it looks on the other truck. pressed it a couple of times with my hand at the bottom, no flex and didn't immediately touch the floor.

climbed in and used my foot as I would normally (heel on floor pivoting from brake to go pedal) and it felt much more like my 95 is. I will know more when I leave headed to work in the morning driving, but I am suspecting the pedal assembly is just worn in a bad spot.

Here are the photos I took comparing the two, I couldn't take a photo after using the zip-ties since it was getting dark, but let me know what yall's thoughts are here.

93 standing outside the door
IMG_5471.jpg

95 standing outside the door
IMG_5473.jpg


93 up close and personal
IMG_5472.jpg


95 up close and personal
IMG_5474.jpg
 
keep in mind I did take in to account for the carpet thickness and the fact they both are under the pedals. both cabs can also have slightly different shapes and not the same between the years too. the zip-ties are only a "see if this help" thing and if it does, I think I might try snagging up on the plastic part of a pedal from the local pick a part yard next time I go. I think it's only held on by a retaining clip and a spring, it should just slide right off the shaft of the pedal assembly. Though not sure if that piece will be the same on a gasser truck.
 
Can you see any wear in the pedal causing this? Removing the add on carpet help?

The fix you have concerns me as there are many recalls on vehicles for the floormat jamming the throttle open.

I recall the OEM floormat for these years was pretty thin rubber.

It doesn't hurt to go over a plan for a stuck throttle. This way one avoids panic by having a couple ideas if it does happen.

Option one popping it out of gear: the engine is expendable in this situation.

Option two of turning off the ignition looses PS and PB and can lock the steering wheel done in a panic. It may not work say if the engine is running off it's own oil.
 
I would need to pull the pedal assemble out to check for wear. I'm suspecting there is ether wear or something isn't up to par on the plastic. before i put the zip-ties on the top tilting it back some, if you press on the lower portion, the plastic will flex some as if it could be cracked from the back side. I will try pulling it out as soon as I get a chance.

driving it to work with the zip-ties holding it seemed to help. so I think I'm on the right track here.
 
Honestly I haven't done much on it. the plastic ties are still on the pedal holding the angle on it. I did venture out the the pick a part yard and took a look at several other trucks and how the pedals were. I found that all seem to look identically the same were the bottom of the plastic pedals seem to sit on the floor (carpet) and pivot there and on the metal rod. (gasser pedals look identical to the diesels too) for the newer trucks, the pedals are held above the floor and can be pressed on at the lower portion with you foot same as my 95. so the drive by wire units are shaped different.

I honestly don't think it's a pedal issue but more than likely due to three cables going to the IP. throttle, cruise, and a cable driven TPS. at some point I want to pull the intake off for some other work including valve cover oil leaks. I will then hopefully get rid of the cable driven TPS for the TCU and look into checking the throttle and cruise cables then. for now I just made certain the throttle cable is in good shape not to get stuck at open throttle.
 
I'm leaning on the cable operated TPS for the TCM. it's internally spring loaded. I need to source a humvee TPS or find a way to make the GM one work on this IP and get rid if the cable for it.

the thought occurred to me since both mount the same but have different doodads to make them turn, maybe using some putty steel set stuff and some plastic wrap (keeping the stuff from sticking to the GM TPS) form a sort of adapter to mate the throttle shaft on the IP (has a slot like a flat blade screwdriver) on the GM TPS that uses a driven roll pin on the shaft to turn it.

it doesn't take much force to turn the TPS so it might actually work once that stuff hardens up. I will need to pull the intake first to even get to the mounting on the IP for it. if not, I will have to ether order a humvee TPS or attempt to swap out the throttle shafts on the IP. I have one for the GM style and a GM TPS.

swapping the shafts does not look fun watching the last youtube instructional I found!
 
dbrannon79 said:
I'm leaning on the cable operated TPS for the TCM. it's internally spring loaded. I need to source a humvee TPS or find a way to make the GM one work on this IP and get rid if the cable for it.

the thought occurred to me since both mount the same but have different doodads to make them turn, maybe using some putty steel set stuff and some plastic wrap (keeping the stuff from sticking to the GM TPS) form a sort of adapter to mate the throttle shaft on the IP (has a slot like a flat blade screwdriver) on the GM TPS that uses a driven roll pin on the shaft to turn it.

it doesn't take much force to turn the TPS so it might actually work once that stuff hardens up. I will need to pull the intake first to even get to the mounting on the IP for it. if not, I will have to ether order a humvee TPS or attempt to swap out the throttle shafts on the IP. I have one for the GM style and a GM TPS.

swapping the shafts does not look fun watching the last youtube instructional I found!
Click to expand...
I will have to peek into my bix of SU carbs that I have to see how I set up a GM TPS on that one carb.
I remember it was not too difficult.
 
Here is the humvee tps and how the throttle shaft mates. uses a flat slot similar to a flat screwdriver.
1728355065145.png

And the normal GM tps for the db2.
1728355168143.png


Notice how the GM one uses a roll pin through the shaft to rotate it. it's deeper than it looks in the photo but my thought is to place some plastic cling wrap over that part and stuff some of the hardening putty epoxy in there. while it's still soft mount it on the IP so it makes the slot impression in the putty. let it cure making me a sort of adapter to go between the humvee IP and the GM tps. I won't let the putty harden and stick to the shaft though. something I can still remove from both the shaft and the tps if and when needed.

Just a thought, don't know if that will work or not. just a hillbilly coming up with ideas to use what I have laying around LOL

if it works I can eliminate the extra cable on the throttle. of course also check the other cables plus lube and clean them if needed too.
 
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