PunkAssRed11

Okay so I have a '92 V6 (unfortunately) automatic 4Runner and just recently when she warms up on my drive to work, about 35 minutes, it wants to die when I come to a stop or will barely idle at around 200 RPMs. THEN to make things even more interesting, I drove to town today which is like barely 7 miles from my house and she started overheating. I have coolant and the radiator is evenly hot on top and bottom, I have no thermostat because I've gone through 6 (I'm not even kidding) and she runs hot if there is one. The water pump is less than a year old, the oil level is fine - it is just running like crap. I am completely at a loss and I kinda need my daily driver in working order. Any ideas?

vital22re

iTrader: (2)

Make sure your cam timing is right and your fan clutch is good.

MudHippy

Well, the good news is, it's not really overheating. But it appears to be because the water by-pass outlet line to the No.1 water by-pass pipe is partially clogged. Which is causing superheated coolant to back up near the ECTS(Engine Coolant Temperature Sensor). The ECTS is then registering the high coolant temperature as it should be. And due to the lack of sufficient coolant flow through the No.1 water by-pass pipe, the coolant isn't able to circulate to/through the radiator and loose any of that heat in an efficient manner.

Then with the ECM seeing that condition as an actual engine overheat based on the signal from the ECTS, it's doing whatever it can to lower the power output of the engine in attempts to lessen the heat build-up. Which would include retarding the ignition timing(or rather not allowing for it to advance) and cutting the fuel supply as much as it possibly can(by shortening injector opening durations). Consequentially, lowering the idle speed in the process. Which is contradictory as a higher, or even normal, idle speed would actually help to cool the engine by providing a higher coolant flow rate though the cooling system. But, being a primative ECM, that's somewhat of an inherent flaw in its design. Meaning, it's limited in what it can do in those situations. The limited factor being an inability to adjust engine idle speed to keep it near normal specs, while also running the programming to help alleviate an emergency overheat condition. Basically, to try and stop the overheating from becoming worse, it decides(as it's been programmed to) that it's "better" to try and cut back on power output at all rpm. Than to not cut power output at all. Since it doesn't have the "brains", and/or the control of other idle speed control mechanisms, to do both things simultaneously.

So...now what? You can try and fix the partial coolant blockage in the water by-pass outlet line to the No.1 water by-pass pipe, or wherever it happens to be between the water pump and the ECTS(such as somewhere within the No.1 water by-pass pipe). Or you, or someone else acting on your behalf, can decide that what I'm saying doesn't make enough sense. Then try and figure out what else to do about it.

PS, the lack of a thermostat being installed isn't actually doing you very much good(if any). That's if any of what I've stated proves to be true. And BTW cam timing isn't adjustable, so you can rule that out. Also, it's not any more likely to be the fan clutch than the thermostat IMO. Both would be very near to 0% likely as to being the cause of the issue, again IMO. Why? Because the most likely way that the fan clutch would fail would be for it to lock up. Thereby potentially causing an overcooling condition(not an overheating one). And all you're doing by removing the thermostat is trying to force more coolant through the/a partial blockage in the cooling system by removing any restriction caused by it's presence(if you even figured that much out).

EDIT: It could be, now that I've had time to reevaluate potentialities, that the ECTS is malfunctioning. CHECK FOR CODES, before doing ANYTHING. That should be enough to tell you if that's the case. And it should be done FIRST THING regardless. Damn, that was a lot of typing for nothing if it turns out the ECTS is the cause. Oh well, maybe somebody reading it can gain some insight on their problem in the future, should that somebody not be you. And I still have one more ace up my sleeve at this point too. But I'm saving that until it would be required. Actually, it's less of an ace, and more of a face card.