454 Sticky Throttle is a death trap

[PlatonicSolid]

What about bad engine mounts letting it shift when placed in gear putting throttle and cable in a bind?

Creative, but not likely since I can replicate it when idling in park.

 

[PlatonicSolid]

Check for any vacume leaks? They are known to cause high idle problems.

I wouldn't expect to be able to kick it back down to normal idle if it was a vacuum leak.

 

[1998_K1500_Sub]

That's an old truck with IIRC a primative ECU and a low serial baud rate. All the same...

Can you put a scan tool on it and see what the ECU's doing with the IAC?

I've got an old version of DIACOM that supposedly works on the older ECUs. I've only used it on a 1991 Beretta and various 1995 vehicles.

 

[sewlow]

The inconsistencies with your wipers is more than likely not inside the column. 93.725% of the time, caused by a faulty pulse board inside the wiper motor.
The boards develop cracks, creating interrupted circuits.
Take a look at how the wiper motor twists & torques around as it goes through it's motions and the cause becomes obvious.
A known problem with these trucks.
There is a factory recall on the board. Whether that's still in effect is a good question. No harm in asking the local dealer.
If not, Dorman makes a replacement. $35.00 or so. Amazon/Ebay. The local jobber is probably a couple of bucks more.
If Dorman makes the part, y'know that it's a common prob.
If you have the patience & the stuff to do, re-soldering the cracked circuits is also an option.
Re-n-Re of the board = 10-15 minute job. 3 screws. 1 plug.
No need to remove the wiper motor from the truck.

 

[Schurkey]

It has many issues that I can live with since it's just a utility vehicle for me (radio and clock no longer function,

Both run by the same fuse? Verify ALL fuses.

intermittent wiper control only works sometimes,

Usually bad solder joints (about six, the larger ones NOT covered in plastic-y goo. Re-flow the solder, fixed.) on the wiper module. Easy fix. Common as dirt. There's write-ups on this site.

brake warning light is usually ON - had 2 different mechanics try to fix this and both failed, but brakes work fine)

Red "Brake" light has three sources for turning it on. Park brake lever/switch --common problem is park brake cables get sticky/seized, pedal doesn't return to proper position.

One of the two hydraulic circuits in the master cylinder has failed. "Safety switch" in the combination valve turns Brake light on.

ABS is unhappy. Turns Brake light on.

Symptom: Throttle sticks high. I'm going 40 MPH on flat road without stepping on gas. Have to put in neutral while driving and kick it to return to normal idle. If I only tap the gas it will stick at even higher idle. After initial warm up in the driveway, everything is fine = settles to normal low idle. Once I start driving it settles at higher idle until I kick it down (stop sign approaching - put in neutral - kick it down - stop at sign. Repeat constantly during journey = it's basically undriveable)

I can reproduce this at the throttle body. Makes me want to put a spring on the throttle to pull it back. Throttle moves smoothly with engine off, thus i believe throttle cable is fine.

1. Clean throttle body and IAC passage with aerosol throttle-body cleaner.
2. Remove ALL cables from throttle lever--throttle cable, cruise cable, transmission TV cable. See if it's still sticky.
3. Somewhat common for the throttle body to wear out, the throttle shaft isn't riding inside round holes, they've worn egg-shaped. Under vacuum, throttle blades jam in the throttle bores. Easiest to replace throttle body, but they can be repaired as said.
4. Connect scan tool, verify operation of IAC.

Possibly related:
O2 sensor code 44 (using flashy light method) - Don't have a code reader, but would like to get one (guidance on what to get appreciated)

There's many possible solutions. My choice is a used-but-usable PROFESSIONAL-GRADE scan tool. (Snap-On Solus Pro, $350 to my door via eBay.) Others prefer the software-plus-cable for connecting a laptop computer, due to very low cost. There are many brands/models of consumer-grade tools on Amazon and other retailers.

Exhaust leak at flange after O2 sensor - Just noticed that yesterday

New "donut", at least that's what it was on my 5.7L. Not fun, especially if the fasteners on the exhaust manifold are rusted--and they always are. I reinstall brass nuts so they don't corrode to the studs.

Best Guess at next step:
Figure out how to fix the exhaust flange leak in hopes that maybe O2 sensor is causing throttle issue.
If that doesn't work - replace IAC

The leaking exhaust flange has nothing to do with the sticking throttle. There's a potential that it's causing false O2 sensor readings, but that's not going to affect idle speed.

Don't replace the IAC until AFTER you've proven it's faulty. Diagnose before replacement.

 

[1998_K1500_Sub]

The inconsistencies with your wipers is more than likely not inside the column. 93.725% of the time, caused by a faulty pulse board inside the wiper motor.
They board develop cracks, creating interrupted circuits.

Agreed. From what little I've seen, the solder joints are the problem, they go open circuit or become intermittent.

I've re-dressed the solder joints with an iron and a dab of solder, and had success.

Inspect the joints closely, visually. Defects are often visible, esp. on the larger connections which might be under strain (where wires and terminals soldered to the board). Smaller connections (resistors, ICs and the like) are not as problematic.

 

[PlatonicSolid]

Wow - Thank you all for the thorough responses!

Here are a couple videos:

The Truck

Throttle response with truck not running

Throttle response running

 

[PlatonicSolid]

2. Remove ALL cables from throttle lever--throttle cable, cruise cable, transmission TV cable. See if it's still sticky.

... sticky throttle cable.

I was convinced it wasn't the throttle cable since there was no resistance with engine off. I was wrong - removed cable an it works just fine.

Here's another video:

Throttle response running without throttle cable

Now I can go through all the other items mentioned - after I find a replacement cable.

Thank you!

OK - I just put the cable back on and now it works fine with the cable.

 

[sewlow]

Sometimes, all the cable needs is a little lubrication on the locomotion. It's probably never been lubed since the day it rolled off of the assembly line.
I bought one of these for my bikes. Works on vehicles, too. For the price, it's worth a try. Cheaper than the price of a new cable.
Several manufacturers, most with names I've never heard of, with prices up to $30.
Get what you pay for I guess, although this one works fine.
Probably all made by just one 3rd. world Co. anyways.
But...It's a cheap tool that works! Imagine that.
Some reviewers complain that they leak & get lube everywhere. Never had that problem.
Could be the ham-f!sted operator's inability to google a youtube vid.

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[PlatonicSolid]

Sometimes, all the cable needs is a little lubrication on the locomotion. It's probably never been lubed since the day it rolled off of the assembly line.
I bought one of these for my bikes. Works on vehicles, too. For the price, it's worth a try. Cheaper than the price of a new cable.

New cable was only $18 and I broke the old one removing it anyway, but good to know this lube toy exists.