Toyota Tundra Discussion Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
Hey guys,

New here, but I'm posting for a friend. I've searched and searched, Googled my brains out, broke a shop light and still can't figure out what's happening with his truck.

He has a 2000 Toyota Tundra with the 4.7L V8. We took the throttle body off and sprayed it down with Throttle Body Cleaner. Then, in my infinite wisdom, I thought it would be good to clean out the IAC valve. I found out, once I removed those that assembly, that this truck doesn't have an IAC valve, it has a Throttle Position Sensor and a Throttle Position Actuator. So, anyways, those two things were removed.

We put everything back together, and now we have a big problem: the truck now idles at 1500 RPM in Park/Neutral. If we put it in drive, it'll "thunk" a bit as it's put into a gear from a high idle and it shifts pretty hard. Also, the throttle will not rise at all until you're nearly putting the pedal to the floor.

We're both at our wits' ends figuring out what is going on. We've pulled that throttle body assembly off numerous times (I swear we can get it off in 10 seconds now) and reinstalled that TPS many times. At first we thought we had to hold the throttle plates open and somehow manage to keep the TPS spring-disc thing in the "open" position (I assume that's what it is) to install it against the metal tabs inside the throttle body assembly. That did nothing. Even pulling the TPS out and just putting it back in without holding any plates open or the sensor spring-disc thing either, still same issue.

My friend really isn't all that happy since he just bought this truck two days ago (preowned, sold as-is, no warranty).

I'm really hoping someone on here can point us in the right direction. He really loves his truck and wants it running normally again.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #5 (Edited)
@Dan Allen: It seemed he had a misfiring problem, so first we wanted to ensure the throttle body assembly was clean of carbon deposits. I thought it was like a normal IAC so removing it wouldn't have caused a problem.

@AKtrd: I find it weird that after removing it, this issue happened. We made sure no throttle body cleaner or other chemicals got sprayed onto it. Just weird that it would suddenly cause problems. And, on the final time of trying to fix the problem, I did remove the TPS and then reinstalled it without prewinding that disc thing, figuring that that is a part which should be able to be taken off and put back on without having to adjust other things first.

Before he goes out and buys a new TPS, is there a way the voltage can be checked to see if it definitely went kaput? Also, what about the accelerator pedal? Is it normal for it to not open the throttle plate until it goes down a certain distance? Because, I noticed that when tugging back on the throttle cable (on the throttle body assembly), it doesn't open the plate until you pull it back so far and then it hits the "catch" that starts to open up the plate. I've never seen a throttle system like this before; any other car, (mechanical throttle, not drive-by-wire) when you pull on the cable, it immediately opens the throttle plate.
 

·
Registered
Joined
·
359 Posts
You would think that the tps would be ok after just removing it and reinstalling. But that is sometimes all it takes. I'm sure there is a way to test them, I just couldn't tell you how. They are cheap and they do go bad. Have you checked for vacuum leaks by spraying around TB with carb cleaner?
EDIT. Just read the latter half of your last post again. It's late :/ or early........ I would take it apart and stare at until you are 150% certain you assembled it right...


Sent from AutoGuide.com App
 

·
Registered
Joined
·
7 Posts
Discussion Starter #7
@AKtrd: We have not. I WAS wondering if there was a leak around the gasket when we kept removing the throttle body assembly. I never thought to try that out. We were puzzled by how weird the throttle cable and butterfly plates were.

Is it normal for these Tundras to have a throttle plate that does not open until you really push the gas pedal down? You would think it's supposed the move the minute you even barely touch the pedal. That is my other big question.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #9
@AKtrd: I spoke with a service advisor at a Toyota Dealership who said that that throttle body is normal when it comes to that. The initial throttle comes from the TPS. He also said that it's possible that the TPS sensor just decided to go bad right at that time. He mentioned getting some Ohm readings to verify.
 

·
Registered
Joined
·
147 Posts
I don't think the throttle cables adjusted properly. I had to take the freeplay out of the cable on my '01. There should be adjustments near the throttle body. You might also need to "recalibrate" the TPS. Sometimes you need to clear the ECM's memory then before starting the engine turn the ignition "on" then slowly depress the throttle and slowly let it up. This sets the "range" for the TPS. You might've screwed the range up by messing with it last time so hopefully this may work. Adjust the freeplay and set the range and see what happens.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #11
@Icon: Thanks, man, I'll give that a shot. I did take up slack on the throttle cable and that did nothing. The battery was disconnected once and I know how the vehicle has to "relearn" everything but I didn't know about setting the range. If it is just the TPS sensor, that'll be great.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #12
Pressing the pedal down to reset the range didn't do anything. I spoke with a tech from a Toyota dealership and he said the way I described how the throttle plate engages with the butterfly plate is normal.

So, with all this going on, is it possible that it's a TPS sensor problem?
 

·
Premium Member
Joined
·
1,968 Posts
If you have your friend work the pedal and you watch the butterfly, does it seem to move normal? Seems weird that it idles high but takes lots of pedal movement to raise from there. Kind of thinking the butterfly may be lodged or hanging up somehow.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #14
@Drunk: Like I said in my other reply, how the plate moves is normal for that setup. It's considered a safety feature in case something were to happen and you had to limp it home.
 
1 - 14 of 14 Posts
Top