New Auto Corolla - Need advice ..

[Andrew]

New 2006 Australian Corolla with 4 speed Auto. For the first 1000 KM there were no problems. Now, at 1500 KM, when the car is nice and hot, I am experiencing intermittant rough engagement at low speeds or from standing start.

Aircon on. I cannot reproduce the problem on demand.

For example:

- in peak hour traffic, feathering the throttle on/off to maintain 5 KM/H up a hill, car will roughly engage 3 times in a row everytime the accelerator is depressed (ie. thud, thud, thud), then will be OK

- from a standing start going down hill at 1/3 throttle, car will engage roughly then jerk (much like a jerky manual clutch start)

- in overdrive on motorway at 60 - 80 KM/H, slight throttle increase at approx 1500 - 2000 RPM will on occasions cause an obvious "wobble" or vibration

95% of the time everything is fine.

Any ideas appreciated

 

[unDummy]

Check your ATF level.

Depending on weather, could also be overheating ATF or an engine running issue.

New vehicle with warranty should be taken to the dealer.

 

[Andrew]

Sorry, should have added that ATF level is normal

 

[Andrew]

Spoke to Toyota and as I expected, unless I can reproduce the problem on demand, it is a waste of time bringing the car in

However, I am coming to some conclusions about this issue and believe the problem could be caused by overheating ATF (auto trans fluid). Problem arises in the following conditions:

- coming off motorway after running in overdrive (makes trans nice and hot because there is a fair amount of slip in O/D) and get stuck in stop/start traffic (stop/start very hard on ATF, made worse being on a hill and because there is no airflow through radiator which contains ATF cooler)

- I ALWAYS run the aircon which is a dealer-fitted unit not a factory-fitted unit (this worried me when I bought car 5 weeks ago). I am thinking they fit big ones to Australian cars because the heat exchanger sitting in front of the radiator is MASSIVE and is as big as the radiator itself (4 times the size of the one on my old commodore ). According to various cooling sites I visited, the radiator/ATF cooler effciency could be reduced to as little as 75% when the aircon is running

- my symtoms (delayed engagement followed by harsh engagement if the above conditions are met) could be explained by torque converter problems caused by overheating ATF in a transmission that shifts beautifully at all other times (ie. assuming no mechanical problem). Torque converter shudder (I get this in overdrive too) is also a characteristic symptom. Ford trucks have quite a few TSBs on this issue and FORD will fit a free auxiliary ATF cooler for trucks experiencing shudder in overdrive

- the A245E trans has a small ATF reservoir (2.9L) and is quite hard on ATF from what I have read. Other cars that have Aisin-Warner auto transmissions are the same. Also, the OEM ATF cooler in the radiator does very little from what I have read (at most 10% ATF cooling compared to after market coolers which can do as much as 60%)

So, I will have to experiment. It is getting cooler now as winter approaches and I will not use the aircon for a while and will do an ATF change. I will see if the problem reoccurs. If it doesn't, I will assume I have found the reason and will get my trans guy to fit an auxiliary trans cooler (very cheap). In fact, additional trans coolers are so cheap and can protect the ATF so well, you might as well do it anyway.

Of course, I could be wrong as I have a hard time explaining why this would happen in a new Corolla with a reputation for reliability and in a transmission that Toyota say can run forever on the factory fill of T-IV ATF (I could write another thread on this issue alone ....). Toyota don't even sell an auxiliary ATF cooler with their 950KG tow pack for the Corolla. I doubt I would be the only one with this problem however, from what I am told, I could easily be the only one sensitive enough to be worried by it

 

[unDummy]

I would consider an additional ATF cooler.
Driving on the highway in OD doesn't add too much heat to the transmission. Once the TC is locked up, ATF is actually warmed by the radiator. There should be no slip when cruising in OD on the highway. But, the TC will lock/unlock/slip as needed when you exercise the gas pedal.

Stop/go driving will raise ATF temp very quickly. Get an ATF filter kit which uses a quart sized oil filter. That'll, along with the ATF cooler, will increase the sump capacity and prevent ATF thermal issues.

If you have an overdrive button, feel free to disable it at slower city speeds. I find that most new cars shift into OD way too early. Its an unnecessary upshift that usually causes another downshift the second you step on the gas again.

The A/C compressor cycling will also add its abruptness to the drivetrain. This is noticeably on underpowered cars. Make sure that you're not feeling the compressor kicking on/off as your driving. It'll feel just like a transmission shift!

 

[Andrew]

Appreciate the input.

The symptoms are similar to what used to happen in my old V8 when I was low on ATF (it had seal leaks in the end). From a standing start, light throttle then a crunch or a thump. It only happens regularly in stop/start traffic after say 10 mins of crawling along at 5 KM/H. I said enough was enough when the other day, I went from a standing start, and it felt like it spun freely up to approx 2000 - 3000 RPM and engaged with a big lurch and a thump. This is what made me think it is the converter.

If I can skip the stop/start, it doesn't happen. Normally in short runs around on the weekend. Everything is perfect.

Also, on the motorway, I can only ever get up to 70 - 80 KM/H in peak hour traffic which is approx 1500 RPM in O/D. From driving the car, it feels as though the converter locks up at 2000 RPM (you can feel the light thud and it revs quickly to 2000 RPM then stops). So most of the time you are running under converter lockup, I think. The whole time you are lightly pressing the throttle, going from 60 - 80 KM/H, with the converter not locked up most of the time. After about 15 mins of this, you get a little "shudder" when the converter locks up ....

 

[Andrew]

I have spent the last few weeks researching the problem of auto transmission hestitation at low speed or from a standing start that results in intermittant rough engagement or jerky starts. Barring any mechanical faults, I am starting to come to the conclusion that this is an issue with the Toyota ECU/TCU and electronic throttle. The problem seems to be present to some degree across the entire USA Toyota/Lexus model range. I can also find a small numer of Australian complaints. Seems to be worst in newer five speed autos.

The symptoms are low speed hesitation experienced as a delay of anywhere from 1 - 4 sec(four sec on very bad examples rendering them almost undrivable) before the transmission engages harshly or with a jerk. Problem is hard to reproduce and can be experienced when accelerating after slow cornering. Often appears in stop/go traffic.

I have been trawling through thousands of forum posts from owners of USA Lexus and Toyota models and it seems Toyota have been attempting to fix it with ECU rereprogramming. For example, in US Toyota Siennas there is a TSB which reduces the hesitation to 0.7 sec. This would put it in line with what I am experiencing in my new four speed auto Corolla. Annoying but not a safety issue.

I am finding this information enlightening but also extremely disturbing. This may be a systemic problem with Toyota and Lexus auto transmissions. I can't find much info about Corollas apart from occasion complaints of "jerky" auto transmissions but it would seem the symptoms are similar.

 

[MonumentOiler]

I've read other complaints of "thottle lag" in the 100 series landcruisers and other Toyota products. Several went to the dealerships and were told that this was "normal".

IR thermometer on the Transmission when you are having symptoms would quickly identifiy or rule out over-heated fluid.

 

[RogerKlugerAus05]

I have a Kluger/Highlander auto and this car suffers from throttle lag which I agree is annoying and can be alarming when you need to throttle up quickly. I believe it is common with electronic throttles, my brother in law has a Land Rover Discovery with the same problem. I am not reporting this as a fault under warranty as I do not wish the dealer to touch my cars other than servicing under warranty, I will live with it.
Roger

 

[obbop]

"Spoke to Toyota and as I expected, unless I can reproduce the problem on demand, it is a waste of time bringing the car in"

I, the Mighty Obbop, feels thine agony.

Chevy/GMC also shuns warranty work for that reason.

Sadly, a GOOD mechanic can diagnose a problem, starting with the most likely problem-causing culprits.

But, it takes a trained experienced mechanic to diagnose a problem. Seems the dealers reserves those mechanics for customers who are paying for a repair.

Those in the shop for warranty work likely get the rookies or semi-competents.

One of those on-the-radio mechanic guys, a local guy with a well-known local shop that has been in business for years, has a one-hour radio show locally every Saturday.

The guy is knowedgeable!!! He does what he can with over-the-phone diagnosing. Folks will call back at a later date and state if the problem had been fixed and if the advice was wrong, close or dead-on accurate. It surprises me how often his diagnosis is correct. Guess it comes from years of experience, along with having access to a computerized database.

The radio guy/mechanic regularly tells the listeners to find a good mechanic and stay with him. He regularly lambasts the many posing as mechanics who do not possess the skills to actually diagnose a problem. He labels the majority of today's mechanics as mere parts replacers who can't fix a problem unless it jumps out and bites them on the nose.

Even then, the "mechanic" may still not correct the actual problem.

In all fairness, the radio guy/mechanic also blames the complexity of today's vehicles, saying that the complexity does make it harder, in some ways, to diagnose and repair vehicles.

Even though onboard electronics can assist in a diagnosis the radio dude adds that there are times when the info given is wrong or leads the mechanic in the wrong direction. He also added that, at times, the onboard electronics themselves are faulty!!!!

Oh well. Time for the Coot to seek out one of those good mechanics who can diagnose problems since the Chevy dealers I have been to refuse to diagnose, resorting to that tiresome "Can't replicate the problem" refrain.