micowen

stalling issue

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Hi all,

I have an '06 yrs ncp91r yaris and for approx. 6 months now its been having an issue with holding rpm at idle. I'll explain as best I can.

While the engine is cold or still warming up, no issue. If the car keeps moving, no issue. After a bit of a drive for at least 20km the car starts having real issues with either idling at a set of lights or being stuck in very slow traffic. 

First of all, the rpm at idle will fluctuate between 750 and 500 rpm. Once it gets sick of this game, which is very quick it tries to stall, which coincides with the thermo fan kicking in. Giving the accelerator pedal a nudge to bring the rpm back up again and holding it there will stop it from stalling, but will be real sluggish when I take off again. If it does stall, then the engine kicks over again with no issue for half a minute, then the problem starts again unless I'm in motion. In the six months that it's been having the issue it has only thrown the one code which was P0172 "mixture too rich".

The mass airflow sensor is clean, throttle body has been cleaned also, new spark plugs, oil and filters. As far as I can tell I'm looking at the idle air control, coolant temperature sensor and o2 sensors.

I have bought myself an ancel scan tool, which is really cool, and it shows no codes, but did show a fault with o2 sensor 2. Doing the test it shows 7 or 8 values that it tests. Although I have absolutely no idea what they mean, the values $86 and $87 are a fail while everything else is a pass. I'll post pics of the fails. 

I did the scan tests on absolutely everything when the engine was cold but the power on, then again while the engine was running but warming up, then again when the engine had been for a drive for approx. 20 minutes.

Without codes being thrown, does this show definitely that bank 1 sensor 2 is up the crapper?

$86.jpg

$87.jpg

$bank 1 sensor 2.jpg

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Just gave the girlfriend's '06 Yaris YRS a bit of a service last Sunday. Cleaned the MAF sensor, the throttle body and the air filter. Al appeared to be ok but the vehicle started running very roughly and threw up a CEL. Scan tool showed a P0172 code which I have since cleared. Yaris was idly very roughly and would not rev, just coughing and spluttering.  Initial thoughts was that I had stuffed up the MAF sensor and possibly the spark plugs need replacing. Next thought is that the air filter and the ignition coils need to be replaced.

I have ordered MAF sensor, plugs and air filters via eBay.

Another suspect is a vacum line which could do with a clamp. After cleaning the MAF sensor again and giving the Yaris a few test drives around the block, it is drivable but could idle more smoothly. I will give an update in a few weeks time.

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As an update, I did previously clean and re-gap the spark plugs. MAF sensor and spark plugs have now been delivered; air filters have yet to be received. 

MAF sensor got fitted Saturday morning and Yaris was back to normal.

After a test drive and further driving this morning, decided not necessary to replace spark plugs until say Xmas. 

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On 4/5/2020 at 10:46 AM, campbeam said:

As an update, I did previously clean and re-gap the spark plugs. MAF sensor and spark plugs have now been delivered; air filters have yet to be received. 

MAF sensor got fitted Saturday morning and Yaris was back to normal.

After a test drive and further driving this morning, decided not necessary to replace spark plugs until say Xmas. 

Its annoying how those little things can cause so much grief.

Bring back the old days when the only electronics in a car was the headlights.

My old 1956 Morris Minor barely had those, and the windscreen wipers changed speed with the engine revs.

But you could repair just about anything in 10 min with parts from the wreckers.

Just because it had a top speed of 70 k/hr and all the pulling power of a sick cat, it was still great.

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19 hours ago, Valkie2 said:

Its annoying how those little things can cause so much grief.

Absolutely so especially when it seemed to be running quite OK before I decided to clean the throttle body and the MAF sensor. I remember the old days of setting the points gap and cleaning the distributor cap. Electronic ignition is a blessing. Shame about all this pollution gear introduced in the 90's and still causing issues with the valves. Guess one of the reasons I like the Yaris is that there is plenty of room to work under the bonnet and it performs well on city streets.

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2 hours ago, campbeam said:

Absolutely so especially when it seemed to be running quite OK before I decided to clean the throttle body and the MAF sensor. I remember the old days of setting the points gap and cleaning the distributor cap. Electronic ignition is a blessing. Shame about all this pollution gear introduced in the 90's and still causing issues with the valves. Guess one of the reasons I like the Yaris is that there is plenty of room to work under the bonnet and it performs well on city streets.

You think petrol cars have issues.

The wonderful old diesels are gradually being choked to death by their own exhaust because of the "pollution" gear they have introduced.

Once upon a time, diesels ran forever had no real problems and were quite good on fuel, as well as pulling like a malley bull.

Now they have PCV to recirculate the fumes, oil, water and crap that is floating around in the crankcase back through the intake and engine.

Because diesels breath a bit heavier, this mess coats the sides of the intake and gives the EGR carbon a nice little place to stick to.

EGR, was designed to take a percentage of the exhaust and again re-circulate it back through the engine. This is to "cool" the exhaust gasses as it cannot burn (having already been burnt) and stops the engine from having such a hot combustion, in theory, this reduces the NOX gasses that do so much damage to people.

But this recirculated exhaust gas has lots of carbon from the burn, this carbon sticks to the walls of the intake, so liberally coated in Crankcase fumes and over time clogs the thing like a KFC eating fat mans heart.

Then, just to make sure that a once reliable and long lasting engine will require more expensive repairs, they add a DPF, (Diesel Particulate Filter) a lazy patch to capture particulates from the exhaust and burn it off into oblivion in an additional waste of fuel called a "regeneration" process.

Of course this little joy has a tendency to clog up if the vehicle isn't driven in a very specific and special manner, or if the wrong oil is used, or if you get a bad dose of fuel, or......etc.....

Toyota has a class action pending because of this little gem. 

The once reliable old diesel workhorse is now a temperamental, breakdown prone and less reliable toy than it has ever been.

My biggest mistake was to buy a modern diesel to tow my caravan, I should have purchased a pre-DPF diesel, I might just do so anyway and get rid of the one I have.

Technology is good when designed well, well made and is robust.

Unfortunately, when talking cars, its never designed well, usually cheaply made and as robust as your grandmothers crystal wine glasses.

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