Need help with 3.0 issue

[Oatsy]

Alright I'll keep this short and simple.. The other day I badly overheated my 1993 3.0 and when it happened the CEL came on. Since then anytime the engine gets up to operating temperature and enters closed loop the CEL comes on and the engine bogs down to where its not driveable. It will idle fine and drive but as soon as you put any load on the engine it instantly feels like somebody stomps on the brakes. Error codes that get are 21(o2 fault) and 25(A/F lean) I've put in a new o2 sensor and new coolant temp sensor which didn't help. I'm out of ideas. It runs and drive fine until it enters closed loop which is when the light comes on and instant power loss. It acts likes timing is being pulled hard..

 

[77'911]

You might do a compression test. Sounds like it might be using some coolant. Is the truck smoking any, or going through oil?
regards

 

[Oatsy]

No none of that is the problem. It is a sensor or electrical problem. I also see I have a code 42 which is for the vehicle speed sensor. This article I think explains it. MOTOR Magazine Article | MOTOR Information Systems So maybe it actually has nothing to do with the fact that it overheated. Just a coincidence that it occured as it overheated?

"The bad VSS signal can cause some very random symptoms during acceleration and/or steady cruise conditions, including intermittent loss or lack of power, bucking or lugging and hesitation or stalling. If the vehicle has cruise control, the driver may also notice that it intermittently disengages for no obvious reason.

With this particular VSS failure, the symptoms don't appear until the vehicle has been driven for some time at operating temperature, so don't expect anything to go wrong when the vehicle is cold. And although these problems occur most often on trucks, they also can occur on any Toyota with a cable-driven speedometer and a reed-switch type VSS."

 

[77'911]

You might at a minimum do a fuel pressure test and vac leaks. You might clear the codes and see what comes back.
regards

 

[Oatsy]

Bump..
This is not a fuel pressure, compression or vacuum leak issue. Runs fine until it reaches operating temp and enters closed loop...

 

[2ndGen4runner4x4]

Pull the thermostat to keep it from getting up to operating temperature. Then see what happens...
I overheated a Camry 3VZ-FE once and it damaged one of the knock sensors. Had the same syptoms that you are describing.

 

[Oatsy]

That is actually what I thought was causing the problem to begin with because it acts like its pulling a lot of timing under load. But my friends who deal with these 3.0's told me when the knock sensor goes bad/unplugged, the motor won't run. I don't have enough experience with these motors yet to know whether that is the case or not. I'd rather not pull the thermostat though since I live in Vermont and it's a little chilly this time of year lol. I know as long as it doesn't get to operating temp I won't have any problems. If I'm not mistaken the knock sensor is located between the heads? Awesome..

On a side note I took a spare coolant temp sensor and plugged it in and left it hanging behind the motor and it still had the same problem. That would be the sensor that tells the computer to enter closed loop I would think. I'm not sure how Toyota has it set up though. Pretty soon I'm about to install a Megasquirt standalone and say bye to all of Toyota's shenanigans :mad2:

 

[Hyde802]

Hey, Its supposed to be 40 tomorrow! Im not one to hate the cold, but this past week was cccooollld! (Its been between -20 and 5 for the past 10 days)

Have you checked your air intake tube for cracks? Air could be getting in after the MAF..(hense the lean code) What do your plug/wires/coil look like? Youre obviously getting spark if its running, but poor spark if the coil is getting to warm could make it run bad (happened on my old motorcycle, but doesnt really go with the lean code)

 

[Oatsy]

Hey, Its supposed to be 40 tomorrow! Im not one to hate the cold, but this past week was cccooollld! (Its been between -20 and 5 for the past 10 days)

Have you checked your air intake tube for cracks?

Yeah I don't mind winter. I love a little snow bogging and trail riding but yeah this recent cold streak was a bit cold for me. A few of those days it didn't get past 0 out here during the day. As for the intake, thats all good :clap2:

All of the ignition components are in good working order. I'm kinda leaning towards the knock sensor/wiring being the culprit now after doing some reading tonight. I found out that the ECU only takes reading from it during closed loop. I haven't actually looked at it yet but from what I have been reading the wiring for it seems to be a common problem. However, I don't feel like tearing the whole top end apart just to take a look at it so I'll either drill and tap a new hole on the block somewhere or make a mount and install another sensor. I'll take a look at it tomorrow and go from there. The engineers that design these things should also be required to work on them...

 

[mikebontoft]

sorry if thos makes no sense. I just got woken up by idiots and I cant read these baby little keys. iys all fuzzy.

did you have to do new headgaakets when it overheatrd? I suspecr you probably forgot to hook up the knock sensir ir or a ground up there.

hopefully ots not bad becaise its under the lower intake manofold.

 

[Oatsy]

No I haven't done headgaskets yet. The motor needs to be rebuilt or swapped this spring anyways which is why there is no way I'm spending the time digging into it to get to the knock sensor. I'll be making a new spot on the block somewhere to run a new sensor. This motor still has plenty of life in her for a weekend trail rig so I'd like to just get by until spring atleast.