thedanned

But Im not worried about off idle. Maybe Im missing something here.

abecedarian

Well anyhow.

Did you adjust the throttle stop and dashpot so they contact the throttle cam? (please say you didn't)
Have you checked for the throttle cable itself holding the throttle open, not letting it close all the way?

thedanned

Non sequitur. Read post 7. Why shouldnt I have adjusted the stop and dashpot?

abecedarian

Well, the dashpot is okay to adjust if it's malfunctioning, but the throttle stop should not be adjusted.

It would seem to me that if the throttle stop has to be adjusted out to get the TPS reading properly, the throttle wasn't closing all the way to begin with and the TPS needed adjusting instead.

thedanned

The throttle was closing all the way, enough to stick closed. I dont think the throttle stop was adjusted all the way out from the factory. I honestly did not measure the TPS before I adjusted the stop, so I dont know what exactly my starting point was. I assumed it (TPS) was correctly adjusted because it was reading correctly after setting the stop to factory specs. IE my immediate goal wasnt to get the TPS to read correctly, it was to see why the throttle was sticking. So perhaps I need to back the throttle stop all the way out again and read the TPS. But then the throttle blade will be sticking in the bore again.


For the record, on my drive to work today (after backing the idle mix screw out) the idle issue has not subsided and seems to be the same. So I will screw it back to where it was tonight and go from there.

I honestly think that the PO had all these adjusters at their extremes to compensate for something. My theory:

I bought this truck from a hay farmer in southern Colorado. Nice guy, just a little backwards on his repairs. I have been pulling house wiring and wire nuts out of his "mods" sinse I took possession. I found the factory zip tube (flex rubber tube from TB to VAFM) badly cracked and letting in all kinds of unmetered air. He put a K$N cone filter kit on it and I think this is when the zip tube cracked. It was a tight fit and that rubber was brittle. I think he then backed the throttle stop out all the way to try and lower the idle (thats the way it works on carbs, right?!!) only it didnt work. He then found the idle screw and jammed that in all the way, which lowered the idle but he didnt set the throttle stop back. I dont think these throttle blades are meant to sit "flush" or whatever inside the bore, thus the reason for the throttle stop. So a few years of driving like this and the throttle blade wore down enough to get stuck and basically "clearance" itself, hence the gap I described in my first post.

I may be waaaaaayyyyy wrong and reading too far into this, but tomorrow I am going to u pull and I will examine some other TBs. Ill take pics of what I find.


Anyway, I should get back to work...

DupermanDave

Yes. Definitely double check the throttle cable. I had an idle issue that was caused not by the cable holding it open, but the butterfly valve just wasn't seating properly and had lots of play in it. I just got another throttle body on ebay for $15.

thedanned

Throttle cable is free and clear

thedanned

So my trip to U Pull It was a successful one. I was able to get a TB, an extra tow hook and some tail lights! My suspicions were correct with the butterfly being "clearanced" too much. The original TB:







And the new TB:




It may not look like much in the photos, but there is a big difference in the gap between each butterfly. Also, there was light visible on the left side of the TB but it didnt show up in the pic. It was hard to get the light to show at all in the pics. Im sure it would be easy for a photographer, but I aint one of those.

I am now idling at 850, my surge is gone and I am a happy camper. Thank you for all the constructive suggestions! And dont worry Abe, I hooked up my wide band O2 and tuned the idle mix screw to stoich.

Something to take note of:
I checked out 4 different throttle bodies while I was there to see if I could make the butterfly stick in the bore with the throttle stop backed all the way out. I was able to make it stick on all four. So I guess the throttle stop is there for a reason.

thedanned

Man, no "atta boy" or "way to be" from nobody? Thats cold blooded.

DJ99

Um, atta boy! For some reason, I wasn't getting my subscription emails to this thread. That's great. Maybe your PO, farmer guy changed his TB valve? How is is possible that it "shrank".

Anyway, it's good you fixed it.

DupermanDave

That's exactly how mine was. That's what I meant when I said it wasn't seating properly. Hopefully this solves your problem.

thedanned

Thanks! I feel validated now!

I think that having the idle stop screw backed all the way out caused the problem, or "shrinkage". The throttle blade is not designed to shut all the way, there is supposed to be a tiny gap when it is "closed". Being able to close all the way causes it to wedge itself in the bore and stick. I was able to verify this with 4 different throttle bodies at the junk yard. So a few years of it wedging itself every time it closed eventually wore it down. Or wore the bore oversize.

thedanned

Dang, now you tell me! Haha guess I just had to see it for myself.

DupermanDave

It's easier to check the VAFM than to remove the throttle body and and check for a leak. But the throttle body was last on the list. The reason I didn't think this was the reason first off because with my issle it was a floppy idle. It would surge up and down and sometimes just idle high. And it wasn't constant. Your problem sounded constant. Maybe your air leak is more severe than mine.

1996Tacoma

SOrry to bring an old thread back from the dead, but I have the same problem you do. High idle and sometimes surging on applying clutch and brake. I took my throttle body off and cleaned it and noticed a gap between the bore and valve. I have a new IAC on the way, but after reading this im convinced i need a new TB too. Thanks for posting this. My gap actually looks slightly larger than yours..boy i hope this fixes it.