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The car thread
The car thread
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Old 9th August 2018, 11:59 PM   #551
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by daqvin_carter View Post
On my 1991 Toyota Previa,
Aka, Toyota Tarago here. I used to jam an LED into the socket to read out my 'Morse code'.
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Old 10th August 2018, 12:46 AM   #552
VenusFly is online now VenusFly  Australia
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The car thread
Okay what did I learn this morning?


The AFM is faulty. I checked its value with a digital multimeter and the value would never be stable and would constantly change in value by anywhere as little as 0.5 an ohm or 5 ohms in as little as a few seconds without even touching the AFM. I might've caused it by probably leaving the lid off of it for too long (and the contact somehow corroded), or maybe it was like that the whole time and the reason why the seller sold the car was because of a problem with it.


Anyway, its a good thing that I bought the spare AFM because I checked the resistance on the AFM contact brush and it was constantly varying by a few ohms. It was EXTREMELY sensitive to touch and every time that I placed my test leads onto the AFM terminals the value would change. There is our intermittent fault I think.

Even breathing on the AFM would change the resistance value read on the contact brush, not kidding. So obviously for a potentiometer that is a bad thing to be happening. Anyway I tried fixing it first by using isopropyl alcohol and some cotton buds and cleaning the contact surface, no change. I then tried using supercheap auto electrical contact cleaner, no change. I then bought out the Deoxit Fader F5, and that changed things a bit, the value went down to about 270 ohms and the value was a bit more stable but it still wasn't 100% stable. So I still look forward to the replacement AFM to arrive in the mail to at the very least completely count it out as a source of problems.


With the Deoxity Fader F5 I simply cut off a strip of A4 paper and stuck it underneath the contact brush and then run the brush backwards and forwards over the piece of A4 paper.


However I don't think that the problems stop there, I still think that the O2 sensor is bad as the tailpipe is still pumping out the fuel, but at least now the idle is slightly smoother than before.


After I have a rest I'm going to go back down and do the LED diagnostic test, I've been reading the paperwork that I printed out and its as simple as bridging two contacts and inserting a LED globe.
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Last edited by VenusFly; 10th August 2018 at 12:53 AM.
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Old 10th August 2018, 01:05 AM   #553
Tubelab_com is offline Tubelab_com  United States
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Quote:
the Toyota Vienta Grande VCV10 model "Widebody" (1993-1997), is down here in Australia rebadged as the Holden Apollo
There were three GM / Toyota vehicles made and sold in the US. There was a joint ventures factory in California called NUMMI, New United Motors Manufacturing. It ran from the mid 80's until the government takeover of GM around 2009. It died along with the Pontiac, Saturn and Hummer brands, as well as Saab and a few other GM owned casualties. The factory was bought at the fire sale, refit and now cranks out Tesla's electric cars.

They made a vehicle called the Toyota Corolla when it came out one door, and it had several GM names over the years as it came out the other door. They were called Chevrolet Novas, Chevrolet Prism, and Geo Prism. None ever sold anywhere the number of cars as the identical Toyota branded car.

The factory also made the Toyota Matrix / Pontiac Vibe. Both sold reasonably well. Some Toyota HiLux pickup trucks were made there. They were renamed the Toyota Tacoma, a name still used here today as is the Corolla.

Quote:
Hence the reason why I own a FWD car today, I'm too scared of the power and ferocity of RWD
They both have their advantages and disadvantages. It comes down to what you are used to. I have driven cars of both flavors with far more power that the tires could put to the pavement. I preferred RWD on the drag strip, and FWD on the autocross track. I had no preference on the street, but it does take some time to get used to what you can get away with in a new vehicle of either persuasion. The more power it has, the longer the learning curve for any new ride.
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Old 10th August 2018, 01:08 AM   #554
Max Headroom is online now Max Headroom  Australia
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Bluetooth OBD dongles are $10.00 on Ebay.....worked on my Camry V6.


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Old 10th August 2018, 01:14 AM   #555
phase is offline phase  United States
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Gm is evil I believe, had OBDII first, onstar, then a rolling terminator from what you’ve described...

What next?

Those Prisms were a great bargain, when people looking for a corolla would regularly overlook them in the classified ad.

I’ll bet the O2 sensor is just fine after the mixture is corrected, and allowed to burn off any contaminates. The O2 sensors are the first thing to show as “bad” with on board diagnostics.

Last edited by phase; 10th August 2018 at 01:26 AM.
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Old 10th August 2018, 02:22 AM   #556
VenusFly is online now VenusFly  Australia
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The car thread
The diagnostic test didn't throw any codes whatsoever. As far as the ECU is concerned everything is hunky dory. There is a test mode and a normal diagnostic mode on this car and I ran both tests and it didn't store any codes whatsoever.


However I also unplugged the front bank O2 sensor and it didn't change the tone or rpm of the engine at all.


Doing this also didn't throw any codes.


I'm going to run through the service manuals O2 sensor tests this afternoon.


Uploadfiles.io - 3vzfe.pdf


^ Here is a copy of the service manual by the way.
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Last edited by VenusFly; 10th August 2018 at 02:35 AM.
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Old 10th August 2018, 03:42 AM   #557
VenusFly is online now VenusFly  Australia
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The car thread
Front bank O2 sensor is fine. Its producing voltage when I start the car, up to 0.9v. It also disappears quickly as soon as I turn the engine off.

Strangely however the O2 sensor settles at 0.8v, it should be at 0.5v....

I'm looking at you mr AFM.

I might be able to do a test on the rear bank O2 sensor tomorrow but not today.


EDIT: AHA! EUREKA!
The engine coolant water temperature sensor is out of specification!!!

Its reading 3.0k ohms when in fact it should be within 1.48k - 1.58 k ohms! (When tested at 80c, I did warm the car up earlier.)

Which means, if the computer thinks the car is still trying to warm up it will continue to dump fuel into the engine to warm it up. THIS IS WHAT THE PREVIOUS OWNER WAS COVERING UP with the butchered and hollowed out thermostat!!!

I think I've found my problem folks!!!

A faulty coolant temperature sensor!

And my problem appeared at about just the same time that I replaced the thermostat and did the big 3 wiring upgrade...


I can't be 100% sure it is the coolant temp sensor but it looks like it might be it. I was wondering to myself why the car was taking a while to warm up according to the thermostat reading inside of the car when I was running it today.


I'll pull the sensor out tomorrow and do a test on it.
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Last edited by VenusFly; 10th August 2018 at 04:03 AM.
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Old 10th August 2018, 05:21 AM   #558
VenusFly is online now VenusFly  Australia
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The car thread
Quote:
Originally Posted by VenusFly View Post
I was wondering to myself why the car was taking a while to warm up according to the thermostat reading inside of the car when I was running it today.

Irrelevant to the test data as this engine has two temperature sensors, one for the thermostat on the dash which is located up on the intake maniifold and one for the EFI computer/ECU which is located down on the thermostat housing.


So what did we learn today? Well a reading of 3.0k Ohms on a Engine Coolant Temperature sensor is a bad thing because these sensors are NTC type and therefore reduce in resistance as the temperature rises. But the engine is all warmed up and has been running for a while and the coolant is at least 40 degrees centigrade. So why is the 3.0k Ohm not lower? Because the sensor is faulty.


This makes complete sense too in the sense that the computer is dumping fuel into the cylinders even though the engine is warm.


And this guy says so:
YouTube
YouTube
YouTube
And... don't touch AFM's. Don't ever touch the insides of an AFM, Don't even look in their general direction, and especially never ever take the cover off.
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Last edited by VenusFly; 10th August 2018 at 05:30 AM.
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Old 10th August 2018, 09:32 AM   #559
VenusFly is online now VenusFly  Australia
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The car thread
yep.


I've confirmed my findings this afternoon. The engine coolant temperature sensor is DEFINITLEY faulty.


It is reading with the ohm meter at 2.955 kOhms when the engine coolant housing is sitting at 47-50 degrees centigrade. As measured with my awesome little multimeter.


According to the charts below the ECT sensor should be measuring 0.6 kOhms.
Attached Images
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File Type: jpg 154-diyaudio.jpg (26.4 KB, 58 views)
File Type: jpg a-bad-engine-coolant-sensor-keeps-you-in-suspensor.jpg (98.6 KB, 52 views)
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Last edited by VenusFly; 10th August 2018 at 09:44 AM.
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Old 12th August 2018, 02:49 PM   #560
VenusFly is online now VenusFly  Australia
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The car thread
I now suspect the rear bank O2 sensor. Today I'm going to go and confirm my findings by testing both as indicated by the service manual.


Its possible that it could've unplugged or the wire could've broken when I was back there working on the rear bank and moving things around.


Today/Yesterday I unplugged the rear bank injector connector on cylinder #1 and nothing changed in the tone of the engine. Not entirely sure what that means. But I did the same to the 3 front injectors and the engine tone changed/engine almost conked out.


It might be possible that the front bank O2 sensor is faulty. Who knows.
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Last edited by VenusFly; 12th August 2018 at 03:04 PM.
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