Strange idling issue caused by extended WOT on interstate?

[T?@\7]

Lastnight I went to visit a lady friend about 30 miles away, and on my drive to and from her place on the interstate I did have the petal to the floor for extended periods of time, just wanting to stretch her legs a little and 'clean the pipes' so to say.Only got up to 65 lol, sometimes itll do 70, idkwtf. Well once i got off the interstate and nearly home, I notice that the truck is idling around 2000-2100 rpms which is about double of normal. I stopped at 711 to grab some beers and upon restarting the truck it starts normally and idles normally, that is until you TOUCH the throttle. once any gas is given shes right back to the 2k range.
After looking at the mechanisms of the TB it seems to me (im not a mechanic at all) that the little spring that is directly associated to the throttle cable doesnt retract all the way, like its lost is springiness.
Has anyone experienced or heard of this before? I did clean my tb the otherday, but its been running fine since and still does, but just idles oddly high.
Thanks for any input.


Ray

 

[T?@\7]

i found its called a "throttle return spring", and i think autozone MIGHT have a variety bag of spring sizes. They are open for another 1.5 hrs so im gonna cruise over. Im bummed because the truck was JUST running super good, i cleaned the maf and TB and ajusted the idle down just a tad (800-900). WIsh me luck!

 

[T?@\7]

throttle return springs: CHECK

Now I need to find out the length of the stock one, i guess i could just take it off, compress it, and make the new one the same length...... opinions?

 

[fourwd1]

If the return spring is really the problem, almost anything tighter should solve the problem. Then you could fine tune it from there. But it may be as simple as the linkage needing a little lubrication.

 

[T?@\7]

what do you mean by linkage? throttle cable? pardon my ignorance...
and what should i lube it with?

 

[fourwd1]

Basically the cable and any mechanical parts attached to it.
Yours is EFI but I've had my carbed truck get stuck at WOT on the interstate before (OK uphill, problematic downhill). Hosing down the linkages on the carb with WD40 (not the ideal stuff but all I had) solved the problem for a while.

 

[T?@\7]

ok, what is the normal amt of 'play' in the linkage when throttle is closed? I lubed up the end of the linkage (where you can change throttle by hand under the hood) pretty well earlier. The thing is once you open er up, or rev it up pretty high and just let it go ( idk the name of that piece connected to the tb) it snaps back, but back to 2000 rpms. i can then move that circular thing that the throttle linkage connects and ends on, about 1/16" or maybe less and then the idle is back to normal.

 

[T?@\7]

found this pic on pirate

that spring has 22-23 "coils", the one i bought has about 40-45 out of the box.....this gives me an idea of how much to trim i suppose. I need to get some fresh batteries for my headlamp!

 

[fourwd1]

Keep in mind, the diameter of the wire used and the diameter off the coil also affect spring rate. I'll bet the one on the right has more "pull" than the one on the left.
But experiment until you find what works, that's how you learn.

Just keep in mind that something else other than the spring may be the real problem.

 

[T?@\7]

yeah, ive got my fingers crossed that this is the solution... I guess if not then its onto the dashpot or tps?

 

[T?@\7]

I'll bet the one on the right has more "pull" than the one on the left.

i agree, what would be the adverse effects of this? harder to press pedal/ more tension on linkage?

 

[T?@\7]

trimmed the new spring, after a couple attempts, down to basically the same coil length as the stock one. The problem was solved for a couples MILES but shortly thereafter the 2k rpm idle was back. Im gonna shortening it by another prob 2 coils and see where that gets me....

 

[T?@\7]

who knows what about the dashpot

 

[turboSR5]

If you want to rule out the dashpot, either back the screw off until it does not touch the plunger or remove it entirely and go for some test drives.

 

[turboSR5]

One more thing to add is...is yout TB filled with black crap on the backside of the throttle plate? Sometimes this stuff creates a ridge that your throttle plate can't run over to return to closed position. Another thing that have seen more of lately are worn out bushings in the TB. It starts out with random high idle problems but eventually progresses to a constant high idle. Only thing to do about that is a new/er TB or get the shaft some new, bigger bushings.

 

[T?@\7]

thanks for the input, turbo. I noticed in another high idle thread that you had a lot of knowledge and ideas. Ill try that dashpot test, and I cleaned my TB like 4 days ago and MINIMAL amts of black gnar came out, but tbh i didnt look that good at the back side of the plate. Its really hard to see in there let alone be able to work with any precision lol. Ill take another look, thanks again.

Ray