ran a search
95 3.0 with 100K.
idle surges especially when cold, from 1000-1400rpm, give or take. not all the time. *seems to go away when in gear (a/t)
i removed and cleaned the thottle body and IAC valve, bled the coolant(there was barely anything in the TB hoses), checked tps. 3/5 resistances checked out ok, didnt check the other 2 since i dont have feeler guages.
VAF is good. fuel filter has never been changed, but ruling it out, since the problem should get worse under high rpm, which it doesnt. couldnt find a cracked hose, ruling that out since the problem goes away when in gear. all wearable ignition parts are pretty new.

when i disconnect the tps, i get a higher idle but the hunting idle goes away. since the tps is good, im thinking ECT, though i couldnt reach it.

i plan on checking ect and egr next. was hoping someone who has been on this board for a while can give some ideas. i read about the brake switch a while ago, and remember it only relating to the 4cyl

thanks for any help

 

I had this at one time too. I noticed that it went away after replacing the O2 sensor. Of course, I had a lean code for it. I also had my HG recall shortly after that too. I know that I don't have the fluctuating during warm-up anymore.

Why would the O2 sensor affect the cold idle? I really don't know. But out of all the things that I did, that is the only one that I can think of that made the difference.

Here's what I've done:
Plugs
Wires
Rotor
Cap
Fuel Filter
O2 sensor
Water pump
Timing belt
Knock sensor wire
TPS

All of this stuff was done in about a period of a month. So take your pick. It must have been one of those things.

 

Hey Hellas, welcome to the board!
I had this same problem in my 3.0. One day, while changing my oil, I decided to change the PCV valve (a bit of a pain) and adjust my idle to the specified 800 RPM. I haven't had the problem since. The PCV valve is on top of the pass. side valve cover, under the intake. You may need to remove a bracket in order to reach it. Once I got the hose off of mine, It was stuck so tightly that I had to improvize to get it out. Here's what you do: grip the base of the PCV valve with a set of vise-grips. If you can't get enough leverage on it, hook the jaws with a battery tie-down (the long, threaded rod with a hook on one end that you clamp down your battery with), put a REAL nut (not the wingnut) and washer on the tie-down with a long, closed end wrench below the washer. Now place a deep socket or sparkplug socket on it's side on top of the intake and lever the wrench on it to pull up on the battery tie-down that is hooked to the jaws of the vise-grip that is clamped to the PCV valve. I hope this helps. It worked for me! Oh yeah, the idle adjustment screw is on top of the Throttle Body, facing the front of the engine bay and has a flat head slot on it. -Chris

 

It was the TPS and plugs for me...02 sensor helped but the initial change was noted when the TPS was completely cleaned. MUCH better performance!

Good luck!

Fink

 

Or you could save yourself the trouble and not have worry about the rubber grommet by paying the dealer $40 to do it. That's what I did.

 

It really isn't that much trouble, and it only cost me a couple of bucks at Advance auto parts. I also had recently adjusted my TPS. That helped it run smoother, but didn't help my fluctuating idle. I'll take my leftover 38 bucks (poor colege student) and take my g/f out for some live music and a few beers. at the jazzhaus, here in Lawrence.

 

CRogge,

I know it's a bit of topic, but have you adjusted the TPS yourself or has someone done it for you?? I'm asking cuz I've been trying to adjust it myself, but the results are nothing to be proud of! :pat:
And what the PCV valve is responsible for??? What are the sypmtoms of it going south???
I have a lot of problems with my 3.slow (if you check all my posts you'll see what I'm talking about) and I'm sure that the problem is with one or two sensors tops! So, I'm trying to figure out which one it is.

P.S. My check engine light is NOT on and I don't have any codes.

Thanks

 

Hi, Hellas, when you disconnected the TPS the ECM went into a limp mode. Limp mode is based on speed and air flow, not on the TPS data. ECM is using the AFM and a speed sensor data to make decisions. Disconnected the TPS told the ECM to run without it. The TPS could be bad you would never know until you tested the other 2 pins for variable resistance.

I am not saying the problem is the TPS. But, trying to illustrate why disconnecting the TPS and having high idle but, no surging didn't help determine if the TPS was at fault.

Have you checked the ECM codes? Just a suggestion.

 

Changing the O2 sensor also helped my rough idle.

 

Lesha30, I adjusted it myself. if you use sections of rubber hose to hold your test leads on the terminals, make sure they are not conductive! I was using regular vacuum hose and the carbon in it was giving me false readings. I wass really confused until I realized that when I squeezed a piece of hose between my terminals and it measured at about 1000 Ohms, I think. You don't really "need" feeler gauges to adjust it, I didn't have any. Just get it as close to spec as you can and then drive it to see how it is. If it feels like it bucks in 1st gear at low speed between idle and light throttle, you need to adjust it again. It helps a lot to have ont of those 90 degree bent screwdrivers to loosen and tighten the screws. Keep trying, you'll get it! It took me a few tries, but I think I've got it now. I hope this helps! -Chris

 

thanks for the responses and the welcome

the pcv valve and o2s is actually pretty new. and its not due for any major work

amusement - yeah, thats why im thinking (hoping) its the ect. its a sensor, that when disconnected puts the ecm into limp mode. what else can do that besides the tps and ect? iat checked out good

the reason im not soo concerned about the tps, is because the feeler guages measure resistance when the thottle is slightly open, and my problem occurs when the throttle is completely closed.

i was also thinking a leaking egr valve (flow, when it shouldnt flow)

i thought for sure people around here would know the problem, i guess its not too common. i plan on getting to the ect sometime

 

Idle problems are uncharacteristic of Toyota's after 88. Cold or hot starts are known but, are easily fixed because of relays corroding in winter salt or just over time. Note: Toyota redesigned and moved relays after 88 and again after 95.5

Wrangling in fuel/air, timing and compression aren't see easy in the fuel injection age. There's no quick "hey, I know what that is" solution. It takes a systematic approach to troubleshoot the problem.

If it were me troubleshooting this problem I would pull any codes off of the ECM. I would run real time sensor readings from the computer to isolate what is working if there weren't any codes. This would identify what is working, marginal, and what isn't working. Having a code reader is a blessing, and having a Toyota service manual is divine.

 

can obd1 store codes without a cel?
it would be great if an idiot light popped up
(oh, the service manual lists tps, ect, egr, fpr among the top things to check for idle/surging complaints)
thanks for your help

 

I had a cracked throttle body(don't know how that happened) - replaced it and the problem went away.

 

i have a 89 lifted 4x4 and mine was doing that then i blew a fuse in my efi replaced it and now my fuel pump dosent work and i have to trip my starter im going nuts trying to figure out what it could be im thinking ignition switch

 

8 year old post resurrection...
Assuming that you have a 3.0 since that is what this original post was working with.
Check COR. Test info here:
http://www.ncttora.com/FSM/1990-1995...e/circuito.pdf
Download your own copy of the FSM using the link in my signature for more testing information.

 

thanks for the info relays good for some reson my self testing unit stoped working i think its my ignition