O. L. T.

iTrader: (17)

Distributor wires rubbing on the serpentine belt.

O. L. T.

iTrader: (17)

The TPS works. When I turn it up it runs my idle through the roof, when I turn it down it does the roller coaster, it therefore works. I changed the MAF and my RPM's came down a lot and the car smoothed out and runs perfect, but I've changed that MAF before and not been happy with the results so we'll see how it goes once it has been driven tomorrow for a good distance.

chiken

You still want to make sure that correctly. If it is not seeing closed throttle then your computer wont be sending the iac the correct idle parameters because it thinks you are giving it a little or a lot of throttle. The hunting is a lot of time because of this. It thinks you are wanting to accelerate so its trying but then it doesnt see the correct feedback from other components that are supposed
To satisfy those conditions and it goes in a loop trying to get to those conditions.

Ali SC3

iTrader: (10)

I agree with chiken, your tps is working, but its out of adjustment. all toyota ecu's start to do that up down dance when the tps is out of adjustment. If you try and fix this by opening the plate more, it actually creates more problems because by turning the plate you are moving the tps to a more friendly position (good), but there is alot more air entering than there is supossed to be (very bad). that 3k idle is your correct idle position according to the ecu which it does not probably understand well, and the very low one is a limp idle that its basically just trying to keep it from stalling out.

the only way to break the loop, is to close the throttle plate a little at a time, and adjust the tps as necessary to keep it from stalling out when you do this (in the direction that gave you the 3k idle). you should be able to get it down to 1k (800 would be better) at least with the tps set in the direction thats currently giving you a 3k idle (not sure which way it turns on the 400). once you get it down into the ballpark and it isn't trying to stall out anymore, the ecu can do the small adjustments for you.

I recognize the sound because on my car if I turn my tps a little too much to the right, its acts exactly like that except my up is 1200 rpm's and my down is like 400 rpm's and things start to get shaky. If I cracked my throttle plate open a little bit more, it would be exactly like yours, and it will do it even if you disconnect your idle valve connector which means the ecu is adjusting things like crazy. my personal theory is that the tps is tied into the decel fuel cut workings, and when the IDL doesn't trigger perfectly this is what happens. Notice when your rpm's get to their peak it sounds like the ecu just cuts the fuel off for a second for no reason, because above a certain rpm it looks to see if you have let off the gas to cut fuel, then it does and you then dip into the lower rpm's (under 2k) where the ecu does not cut fuel because its only designed to work at cruise, and since you have alot of air coming in it climbs back again. So I guess you can say it is air/fuel related but it is caused by the TPS. the fix is easy though close the plate up some and turn the tps all the way to the side that keeps the engine running, then turn it back very slowly till it stalls. once you find the stalling point, then move it back to a little before that point, and tighten it down. reset the ecu for good measure and enjoy.

O. L. T.

iTrader: (17)

I'm listening to both of you, I'm just saying I set my TPS according to the settings on here just to make sure it wasn't it, even though I've ran this way for YEARS with no issue, and it's not changing anything. The MAF has made the biggest difference thus far.

There is no middle ground on this TPS, it's either roller coaster or skyrocket. I've backed the idle screw down to null and no joy.

chiken

Setting the tps with voltage readings per the transmission section is the fastest and easiest way but not as accurate as the resistance/feeler gauge process. You pretty much measure the voltage at two pins and adjust the tps until it reads 0 volts at closed throttle and then should jump to 1 volt just off throttle. Its a quick 30 second check/adjustment. I can post the process and pins if you would like when i get home.

Like i said, i think you should try to set all base settings to factory spec and go from there, it may fix it and it may just make it easier to diagnose.

Your MAF could have fix a lot if the temp sensor on the old ones (i think you said you replaced it once before) a bad intake air temp sensor usually located in the MAF housing can cause very rich conditions and exaggerate other problems that may be occurring. So yes your MAF may have fixed part of your problem but like you said, its intermittent.

Ali SC3

iTrader: (10)

So originally when you had the problem the high side was a normal idle, and the low side would stall out when it happened randomly. If the TPS was in the correct position when this was happening (skyrocket position) and the throttle plate mostly closed like stock, I would have to think it may be a problem with the IACV. if you have never cleaned it that is worth a shot, sometimes they stick from carbon around the passages and sometimes the rod on the IACV istelf will be rough when you try and turn it for it to move in and out, it should turn very easily, and a few shots of wd40 frees them right up again in most cases.

O. L. T.

iTrader: (17)

I'm sure I have the TPS correct, but if you get the numbers I'll take a look at them. She drove the Lexus yesterday and said it was still doing it. For whatever reason I corrected it for a little bit. It seems to happen AFTER the high idle cam kicks off.

Ali SC3

iTrader: (10)

thats the idle air control valve adjusting, there is no fast cam. Its on the very front of the 1uz intake, a round black plastic thing with a large connector held on with 3 or so screws. if you pull that off off and find a bunch of crud in there thats the problem, it controls fast idle and regular idle. If you find yourself stripping those screws, attack them with pressure pliers from the side and they usually break free right away.

chiken

From the Transmission TPS settings in the service manula.

1-turn ignition switch on. (do not press brake pedal at any time)

2-check voltage between terminal TT and E1 of the DLC2 connector. I checked mine at this one inside, it may work outside as well just pulling on the cable but I used the pedal just to see how much play there was before it sensed throttle. You should see almost zero voltage at closed throttle, it won't be exactly zero but it will be under 1 volt. Then as you gradually press down it should increase by 1 volt increments. So if you check the voltage at closed throttle and it's not zero, then adjust it until it is closed to zero and goes to 1 volt when you just tap the throttle. I loosened the screws enough to hold the TPS while I played with the throttle but enough to make adjustments so I didn't have to keep loosening the screws.

Like I said, if you don't have less than 1 volt at closed throttle, your computer thinks that you are giving it gas and it will be sending conflicting outputs to your IAC valve. If your IAC valve is dirty then it will just make the situation worse.

MooJohn

I fought this forever, testing everything and finding nothing. I finally replaced the IAC after cleaning & lubing it and that fixed the idle issue for good. This was after a ECU capacitor repair as well -- needed that anyway.

The trick to the TPS is that it is two sensors in one. The most important part is the idle switch. It is binary, and that's what you want to trigger just before the throttle is fully closed. The instructions say to use a feeler gauge to get this exact but I admit to eyeballing it.

The variable-voltage sensor that tells the CPU how much throttle you're giving it won't cause this situation. It is used for fueling and demand calculations, not idle.

You can plug a 4-pin computer power plug into the TPS sensor to test the pins without splicing factory wires. I just cut one off a dead power supply and then you can test resistances and the idle switch quickly.

O. L. T.

iTrader: (17)

I'll check it. I've looked at a picture for tonight instead of going out.

Thanks all. I'll look at everything in the AM.

O. L. T.

iTrader: (17)

I cleaned that spot, it was a LITTLE dirty, but nothing crazy. Didn't change the fact. I can touch the little air push rod with the rubber boot behind the TPS and kill the engine or raise the rpm through the roof and that made me wonder if it is not electrical how do you know when it is bad?

Also, this is most important to note, I have a check engine light that is off when cold and immediately starts coming on very dim and increases over the next 1.5 minutes until the car has some warmth to it then it is at full brightness. Since this light came on I have had this issue. It's a sensor. Adjusting the TPS and throttle plate from here to hell and back don't seem to put me in the right spot. The TPS is working and responding to changes. This dim engine light issue that gets brighter as the car warms up is whatever the issue is.

Also below is the pic of the before and after on that part which made no difference in the way it runs.

chiken

The check engine light seems very strange. It shouldn't be dim or bright. It should just be on or off, maybe something to do with the ecu rebuild or poor connection with the bulb. The fact that it comes on after a couple minutes probably means its something like you think, a sensor or something that the ecu checks once its out of cold start mode and looks for feedback like an O2 sensor heater or something. You said you cant pull codes anymore?

O. L. T.

iTrader: (17)

I need to spend a full day with this thing and really get to know it's moods. What I do know is the check engine light is variable as I have documented it before here.

https://www.clublexus.com/forums/per...ssue-ever.html

Tonight I did a lot of things so IDK what was the fix, but the light went off and the car runs properly. I'm sure tomorrow it will be back up to it's old tricks again and I can continue to figure out what the deal is.