scope103

1994 6cyl (3VZE) 4wd

After reading the marvelous success stories by those who have carefully examined their Throttle Position Sensors, I decided to do the same, with the help of the FSM (Factory Service Manual). Now I am much more confused ...

I think I need to know what the dashpot is supposed to do.

Here are the clues:
1. The truck runs perfectly (which may be enough to just stop right here).
2. The TPS IDL-E2 reads infinity at throttle closed (should read less than 2.3k ohms). (I'm only 80% sure on this test; the connector is very hard to reach)
3. When running, the throttle opener (at the top of the photo) correctly retracts about 5mm, but the throttle does not follow it. The throttle is sitting on the throttle stop screw (not visible in this photo). Idle is dead-on at 800rpm. When vacuum is removed from the throttle opener while engine at 2000rpm, the idle will drop to 800 rpm when throttle released (should be 900-1800rpm, so the throttle opener is not "opening" the throttle).
4. The dashpot (bottom of photo) is fully extended with throttle closed, but does not extend farther when the throttle is opened. Should it? Therefore, the dashpot does not hold the throttle open for the one second it should take to gently close. The dashpot does not want to compress further (with finger pressure) either.
5. When the "special service tool" (paperclip) shorts the TE1 to E1 points on the diagnostic connector to set the timing, the idle speed does NOT change when the tool is removed. Should it? Could this be a hint that the truck doesn't "think" it is at idle because of a bad TPS setting?
6. The Air Valve (idle adjustment) has very little effect on idle speed.

My WAG (wild-ass guess) is that long ago the dashpot failed "extended," holding the idle too high. Rather than fix the dashpot, someone carefully reset the dashpot adj screw, or the idle speed, or the TPS, or the throttle stop screw, or all of them.

Your insight will be appreciated.

94 Yota 4Rrunner

well first off i hate the dashpot myslef, i noticed that it holds it open a bit sometimes so i took it off lol and just left the long screw there.

also the the test u did on ur TPS is right, as long as u measured the top 2 terminals, it should have continuity, and when u open the throttle it should read infinant. in respect to the throttle opener, first set ur TPS once done and set with the .020 feel guage and .030 guage, set the throttle opener to the point just after the meter reads infaniant on the top 2 terminals, this should give u a base line to tinker

hope this somewhat helps

fastpakr

I'm on the fence about just making this as a new thread, but it covers a lot of the same topics so I'll bump this. A friend left his (new to him) '90 4Runner with me for a few days because I wanted to troubleshoot a few of the issues he was having. The primary issue was a significant lack of power.

While trying to check the base timing I discovered that it did not change at all when shorting the pins at the diagnostic connector. Based on searching, a likely cause was a misadjusted TPS. As I'd planned to clean up the throttle body anyway, I went ahead and pulled the whole unit. I've since discovered that the dashpot is not extending when the throttle is opened. Not too concerned about that as it should just be an emissions issue rather than a real drivability problem.

I'm more concerned about the discrepancy between this throttle body assembly and the one described in the repair manual PDF's and pictured above. This one has no vacuum throttle opener at all. It looks in the photos above like it should be sandwiched between the TB casting and the TPS. Was the design changed over the years or has it been removed? I'll take a picture if that's necessary, but I'm hoping that somebody just knows the answer off the top of their head. It also looks in the photograph like there are four lines going to the top of the TB. The unit I'm staring at only has three (R, E, and P from left to right).

Anybody know what's going on? Thanks in advance.

Jay351

I dont have one of those either...

fastpakr

Interesting. Well that leaves me all sorts of confused. Need to make sure all the idle adjustments are set right, but all the documentation seems to be geared towards a slightly different TB. Do you know where each of the adjustments are on yours? I assume the one on the engine side, top front of the TB is the warm adjustment (just under the two vacuum lines that come across the top). Not sure about the cold idle and a/c idle up screws. Any help you guys can offer would be tremendously helpful. I've been searching through the threads here and can't find an explanation that makes sense to what I'm seeing.
Thanks in advance. I'm pretty comfortable with a Ranger, but a little new to Toyota trucks.

Sparkimus

According to the FSM, only trucks with an automatic transmission have the throttle opener.

xxJDxx

This is the problem I'm having. When i stop my 4runner will occasionally idle around 1100 rpm, with a slight backfire and rough idle. Its the throttle staying open slightly. If i go and manually push it closed it returns to normal idle.

Is this the DP holding the throttle open slightly??? I've been messing with the adjustment screw for weeks trying to solve this problem....

OutlawMike

Well, I have an '89 V6 Auto, and I do not have a throttle opener. Maybe they added them to autos after a certain year, but my first gen does not have one and my '89 FSM does not show one.

JamesD

I'm thinking more like automatics with California emissions. Mine is a 94 4Runner stick and it does not have it. My 89 V6 auto did not have it either.

James

OutlawMike

Mine is a California rig. Must be something they added for the second gens at some point. Mine is the last year of the first gen rigs.

Blue Toy

I know it’s been a while but mine is doing the same so I’m wondering what you found on yours and the fix. Tia!