my poor 4Runner... question on TPS

[channer]

Hi

my 4Runner when warmed up will either idle at 500 or 900 rpms. It doesn't fluctuate when I am at a stoplight... it's either idling at 500 or 900 rpm.

Is this a sign of a bad TPS? or is it something else?

I'm still trying to troubleshoot a stumbling problem that have under load (1700-2200 rpms). I sorta notice my stumbling problem occur more often when the 4Runner idles at 500rpms.

TIA... dave

 

[DailyDrifter]

What year? Clean the maf.

 

[channer]

What year? Clean the maf.

1990 4Runner, v6 3.0l, 5speed, approx 135ks, I've...
- changed plugs, wires, rotor, cap, 02 sensor
- clean egr
- swapped out computer, maf/air flow sensor

so far, no matter what I do... the truck still idles either at a stalling 500rpm or smooth 900 rpm... and that 1700-2000 rpm stumble under load is still there. Still trying to figure if there is a correlation between the two!!!


tia...dave

 

[DailyDrifter]

check the tps with a volt meter. Back probe the middle wire on the TPS. KOEO slowly sweep the tps and see if voltage momentarilly(sp) drops.

 

[GNeric]

Is this the same one you were going to swap the VAF out with a junkyard unit? There could be a worn spot on the used units in the idle and cruise areas. You would need to cut the silicone seal off the plastic cover and look at the black portions that have the resistance built in and see if they are worn. If so, replace with good unit.

 

[gunslinger]

It very well could be a funky TPS. These things are very picky about the settings.
Here's how to check/set the TPS properly:

1. Loosen the two set screws that secure the TPS to the throttle housing. (DO NOT REMOVE THE SCREWS)
2. Connect an Ohmmeter to terminals IDL and E2 of the TPS after removing the connector. (The bottom 2 as you look at the TPS)
3. Insert a 0.62mm (0.024in.) feeler gauge between the throttle stop screw and stop lever.
4. Rotate the TPS counter-clockwise and slowly back clockwise until the Ohmmeter just looses continuity, (infinite ohms).
5. Secure the TPS with the two set screws.
6. Remove the feeler gauge and recheck TPS setting.
7. There should be continuity with a 0.50mm (0.020in.) feeler gauge inserted in the stop. There should be NO continuity with a 0.77mm (0.030in.) feeler gauge inserted in the stop.
8. Remove the Ohmmeter and reconnect the TPS connector.

 

[channer]

Is this the same one you were going to swap the VAF out with a junkyard unit? There could be a worn spot on the used units in the idle and cruise areas. You would need to cut the silicone seal off the plastic cover and look at the black portions that have the resistance built in and see if they are worn. If so, replace with good unit.

GNeric... I've tested with 3 junk yard unit and all three behave the same way!!! Good thing that the wreckers give 3 month warrantee On the 2nd one, I pulled off the plastic cover and saw what you were talking about. I gently tried cleaning with a Q-Tip but that did not help.

Gunslinger/DailyDrifter... I did not get a chance to test the TPS today. Rain all weekend.

Today, I did pickup a complete throttlebody with TPS, another Air sensor, 02, ECM, distributer for $50 today from someone parting out their 4Runner.

Guess what... the truck ran fine today... go figure

thanks again... dave

 

[GNeric]

It ran fine without doing anything to it? It saw you were serious about fixing it and started acting normal for fear of being worked on some more. We get a lot of these at the dealer and customers get frustrated that they can't make it act up for us. We get it to act up a mojority of the time and get them fixed up. GOOD score on the throttle body.

 

[channer]

It ran fine without doing anything to it? It saw you were serious about fixing it and started acting normal for fear of being worked on some more. We get a lot of these at the dealer and customers get frustrated that they can't make it act up for us. We get it to act up a mojority of the time and get them fixed up. GOOD score on the throttle body.

The problem is random. No error codes!!! I just can't figure out when the stumbling will reappear again. Right now... 2 days of smooth driving & counting!!! Last mod was the sparkplugs 3 weeks ago.

I took it to the dealership... it would cost $120 just to put the scope on it and $80 an hour to try and figure it out. I had a good discussion with the technician... he said I did a lot of the trouble-shooting. He said to take it in immediately when the problem happens. Problem is the dealership is not close by.

I found 2 Toyota threads, one mentioned spark plugs, the other timing belt. The technician also mentioned sparkplugs... so I got new plugs, it ran fine for 1 day, and then the stumbling came back!!!

I finally was able to score a complete TB & TPS. I wanted to replace the complete TB & TPS so I would not have to adjust the TPS myself.

I still have to check the TPS but my next change will be the TB when it starts stumbling again

dave

 

[gunslinger]

What plugs did you use? Denso or NGK ONLY in these things.

 

[channer]

What plugs did you use? Denso or NGK ONLY in these things.

Hi

I've put in NGK Platinums, the last 3 times I've changes plugs & wire. When I went to the dealership, the technician suggest regular NKG or Toyota/Denso. So I bought & installed cheap/regular NKGs about 3-4 weeks ago. That was the last change I've made to the truck!!

It ran without any stumbling for the first 3 days... and I thought, PROBLEM SOLVED... but the stumbling came. It's random. I can drive for days without the stumble, and then it re-appears for couple days. This has been going on for the last 2 years... its been stumbling more since the end of summer.

I've been running fine since Saturday!!! GO FIGURE:biggrin:

dave