Chronicles of a High Idle Post Tune-up

Hi all,

Former lurker here and new Taco owner. From searching, I know a lot of people have had this problem. I also know that a myriad of solutions have been found for different trucks. I figured I'd relate my own experience so if I find a solution it might help others out.

What we're working with–
Year: 2001
Model: Taco TRD 4X4 SR5 5 spd X-Cab
Engine: 5VZ-FE
Miles: 234,xxx
Mods (from previous owner): K&N CAI, silly throttle body spacer

What I did 9 days ago (all OEM replacement parts/filters)–
-Replace valve cover gaskets, cam plugs, bolt washers, spark plug grommets, clean half moons (all per online write-ups for fix leaking covers, did the same things on my 4runner last year with no issues)
-Replace plenum gaskets
-Replace PCV & grommet
-Replaced plugs & wires (dielectric & anti-seize)
-Tossed silly throttle body spacer
-Adjusted throttle cable to compensate for absent spacer
-Clean MAF sensor (MAFS cleaner)
-Clean plenums (brake cleaner)
-Clean throttle body (carb cleaner, followed by a little brake cleaner on metal components after I got impatient)
-Clean and oil K&N (actually did this a week before everything else)
-Seafoam in crank & tank (also a week before)
-Replace fuel filter (10 minutes after symptoms appeared)
-Change oil (10 minutes after symptoms appeared)
-THOROUGHLY cleaned IAC (w/ brake cleaner, 5 hours after symptoms appeared)
-Checked every vacuum hose 1.0X10^98 times

Symptoms:
-Hard warm start, actually improved after the tune-up but is still present to some degree
-Idles at 1300-1500 cold at startup (normal I think?)
-Idles at 950-1250 when warm (not-so-normal)
-Idle was initially extremely rough at 600 post operation, but I pulled the FI relay and it smoothed out, just high
-When I drop the hammer at a low RPM, the truck stutters and the drivetrain sounds like it's exploding

Analysis:
-The butterfly has a bit of space between it and the throttle body, so this is probably allowing uncompensated air through providing a lean idle and high RPM
-The initial hard warm start indicates a possible ECT sensor gone bad, which could also provide an unnecessarily high idle and possible hesitation if it thinks it's still cold
-The clunk/stutter is probably a drivetrain in need of lube. Any persisting hesitation will be masked until I rule this out

Plan:
-Lube the drivetrain this week
-Change all 3 diff fluids and tranny fluid next month and see if hesitation/clunk persists
-Possibly replace ECT sensor next month
-If ECT sensor doesn't fix it, replace TPS
-If TPS doesn't fix it, find a replacement butterfly if they exist or get a junk yard throttle body.

I sincerely apologize for the lengthiness of my maiden post, but please feel free to ask questions/offer suggestions. This is a hybrid help me and write-up thread. Thanks for a great forum.

 

234k has the 02 sensor ever been changed?

 

Valid question. The only service record I have at my disposal is a 150,000 timing belt. I think the O2 sensor is worth considering, but my mileage isn't bad (15.6 on the first tank full with lots of WOT since I was testing the engine).

I should also have noted in my original post that there are no CEL's.

 

I think the 02 sensor only lasts about 130k but I could be wrong.

 

Noted. I'll add that to my To-Do list.

 

This is a good call as my O2 sensors died around 80K. They high idle is typical after a mass air and TB cleaning but it typically goes away after a few miles and a couple of days.

Defiantly sounds like you are getting unmetered air into the intake somewhere.

 

Mine idled high after doing plugs, MAF, etc. Resetting the ECU fixed it.

 

Sorry to hijack this, but what writeups did you find most helpful? I've got a 98 4Runner that I'm about to do this on.

 

I'd read through the whole thread. There's some valuable tips and tricks.

 

By resetting the ECU do you mean pulling the EFI relay, disconnecting the battery, or something else?

 

I pulled the EFI relay. Can't remember how long. 15-30 minutes maybe?

 

Gotcha. I did this with my 4Runner and it worked fine. I had the relay out of the Taco for quite a while but no dice.

 

Anybody know what this dampener thingy does? I just noticed it's keeping my butterfly ever so slightly cracked. I'd think that the TPS would catch this and adjust accordingly...maybe it is and that's why the idle is smooth but high.

I've been hesitant to adjust it because it still has the factory seal paint on it, so it must have been right at some point.

 

No dice on the damper thingy. I depressed it all the way so the throttle assembly wasn't touching it and the butterfly still didn't close all the way. Same story with the stop screw at the top. There's something else that holds the throttle open.

I illustrated this in the pics. In the first one, you can see a gap in several places as I depress only the spring. In the 2nd pic, I'm also pulling the throttle assembly until it closes all the way (about 8 lbs pressure if I had to guess).

Is there any sort of motor on the TPS side of the throttle body? What else might hold butterfly open just 1/32"? My linkages all have enough slack in them.

Bonus: the last 2 pics are why you should always clean your IAC on a 200,000+ motor.

Edit: forgot to mention, this is all relevant because I discovered today that the motor idles beautifully at 600-750 if you rotate the throttle body that extra 1/32" illustrated in the pic.

 

http://www.yotatech.com/f2/auto-vs-manual-transmission-throttle-body-3-4-a-191672/

This gentleman seemed to track his high idle down to the same problem, but I think he just replaced his throttle body. Not the route I'm looking for, as I'd like to solve the actual issue here for myself and others with this problem.

Random update: after careful observation, I have noticed a pulsating stutter usually between 3K and 4K WOT, but after 4K it takes off like a raped ape. There's still a stumble anytime I drop the hammer as opposed to rolling onto the throttle.

 

I had similar idle problems with 4Runner. After cleaning the throttle body my idle problems became worse and I also had the problem of the butterfly valve not closing all the way. I had a local shop shim the shaft so that the butterfly valve wasn't hanging up on the side of the throttle body. They also added an extra spring to help pull the valve closed. After that very seldom would my idle would be high. I ended up buying a used throttle body off of ebay. The ebay one was from an automatic so I swapped the linkage setup off my original throttle body onto it. I have only been driving it a few days since swapping throttle body's, but so far it idles perfect.

 

I just discovered how cheap these guys were on eBay. So the linkages swapped ok? Because there are no 4X4 MT V6 throttle bodies on eBay right now.

Before I commit to this route, I'm going to swap the TB from my wife's 4Runner onto my truck this weekend and confirm that that fixes the problem.

 

The linkages swapped over fine on mine. However I have a different setup than what you have pictured. On mine the damper sits lower on the the throttle body and is sitting more horizontal. The damper also directly contacts a tab on linkage assembly, I don't have the vertical rod like yours.

 

Hmm, well at least I'll get a trial run with my 4Runner's first before I spend the money. My 4Runner is a 99 and it doesn't have a damper at all. Maybe that's a manual only feature? I included a pic of the 99's just for anyone who might be curious. By the looks of things, the linkages should work out. I may not even need to change them out, I think I can just leave the tranny linkage space empty.

 

The damper is on manuals only. Just below the throttle cable where the two tabs make contact is where the damper is on mine. I ran mine for a couple days before switching the linkages over. It will work just fine, but the linkage setup for the automatic has a lighter spring pressure because it normally has the trans kick-down cable helping pull the throttle closed.