It seems that whenever I figure out one problem, another one is always waiting for me.

Having solved 2 idle issues, thanks in large part to all your replies , I am trying to figure out the last (hopefully) idle issue.

The idle, whether in park or in gear, is extremely low. It is lower than it should be when the engine is cold, and when it warms up, it drops to 400 RPM or sometimes even lower, to the point of almost stalling.

Now, that in itself is not so interesting. BUT, what IS interesting is that, when I use idle adjusting screw, it raises the idle.. for a while only. After some time driving it, maybe a day or two, the idle returns to extremely low. It did it to me twice. Interestingly, it makes no difference whether engine is in park or in drive, the idle is essentially the same.

The first time, after doing TPS adjustments, I set the idle to proper speed (750 or 800 RPM) and set timing. A couple days later, the idle was at 500 RPM or lower, no fluctuations. Just steady low idle. I had no time to mess with it so I just cranked up the idle adjustment screw to bring it to about 800 RPM. Well, behold, in a day or two it ends up down at 400 RPM again.

Having someone else drive my car, I did not want to take chances of it stalling if the problem got worse, so I cranked up the idle screw again, bringing RPM to about 900 RPM. That did it.. for a day or two. Now, the idle has returned to about 400 RPM. It even gets lower when the engine is hot.

The only correlation I was able to find is that the idle seems lower when the engine is very warm, like after prolonged hard driving. But, it is low througout the temp range, so I know that it is affected even when cold.

Considering all the work I did with the vehicle, the only theory I have is that, since the idle self adjusts to a lower value, that could be the ECU. That means the ECU is adjusting some parameter based on some sensor input, and that input must be incorrect. Besides the idle, the truck runs beautifly.. almost perfect.. as perfect as a 3VZE engine with lots of miles can run. As long as I keep my foot on the gas, everything is perfect. The thing purrs like a kitten and runs like a champ (if that can be used to describe this engine)That in itself eliminates whole bunch of possibilities, like bad spark, bad timing, low fuel pressure, plugged cat, etc.. I really dont have any complaints about the engine performance (except I would really like 3.4L in there instead )

Other things to consider:

TPS within specs and adjusted
Throttle body cleaned
Idle adjusting screw cleaned
Seafoam application a while back, no change in behaviour
MAF (afm) within specs, and it appears air temp sensor is too
No cracks in the air induction system, that I can find anyways
Air Box Extreme Mod with K&N filter.. but I had it for a long time this way with no issues


---> ---->
So... anyone have any thoughts on where to start looking ? Thanks a lot for all the ideas you can send my way!

 

I would check the leads coming off the distibutor. The signal generator may be out of spec and causing the ecu to adjust all the time. Unfortunatley you have to get a new distributor to solve this problem. Check the code as well to see if anything pops up. Also, has rad sealer ever been used in the vehicle? The coolant line that runs through the throttle body on mine was clogged shut and was causing wierd idle problems. Just some thoughts and good luck with it.

 

Great thoughts.. I forgot to mention that there are no codes in the system. But the OBD in these older trucks is next to useless, based on my experience.. it tells you when there is a problem just about only when the truck will not run, and then wouldn't you know it anyways ?

I have no idea about radiator sealer, I have never used it but maybe the previous owner... I will look into that. I will also try to troubleshoot the signal generator and see what comes up. Thanks, and keep them ideas coming.

 

My truck did the same thing for a long time, so here's what I did to correct the problem: 1st I took the idle screw completely out and I cleaned it real good and also the t-body, this worked for a week or so and then when she warmed up, 400 - 500 rpm idle, so I turned the idle up to approx. 1500 rpm's and I back the idle screw that opens the throttle plate down and adjusted the idle here to get it back to 850 rpm's and finally I pulled the efi fuse and ran her. It's been months now and I haven't had a problem yet!! When you back off the idle screw for the t-plate be careful if you go to far your t-plate will stick giving you a hard accelerator pedal! Make sure after you do this you recheck your TPS!
Good Luck!
Harry

 

Oh yeah,
Also, check that the pcv valve is working properly. It will force oil into the intake and can clog the IAC portion of the intake (on the side on the intake under the TPS. It has a cover that can be removed very carefully). This fills up with oil and the gasket can go bad or just clog up the works.

Just another thought.

 

Forerunner,
Did you ever figure out what caused your idle probs? :pat:

 

You 2nd gen guys should have an idle air valve (not positive)....
...if so take that out and clean it as well (this is what really controls the idle on a 3rd gen....ie the self adjusting part)

 

Hi i just got open an account with yotatec and i dont know how to post yet but anyways i have a idling problem with my 95 4runner its a v6 5speed. everytime after it warms up the idle stays at about 500 rpm and go up and down sometimes feel like its going to stall but doest and never goes past 1000rpm. any body know are have any ideas whats going on? thanx