1az-fe Engine Problems

[Pascua Gomer]

Browsinga forum on the (New Zealand) Automobile Association website whilst researching options for a new car for a family member, I noticed repeated advice to avoid the D-4 petrol engines because of carbon build-up causing problems such as rough idling. The recommendation to owners of the engine was to use 98 Octane fuel to minimise the problem. (Example here)

The only reference to such a problem that I was able to find on the web, other than the original NZ AA forum, was an item about the first generation (2001-2005) Premio on the Kenya Toyota Club homepage

I don't really see what switching to 98 oct fuel will do.Putting higher octane fuel in will only help if either you alter the the timing to make use of the extra knock resistance or it's knocking already.

The only thing I can think is perhaps the engine is in a different state of tune in NZ,perhaps for emissions reasons or the quality of the fuel over there as I've never heard anything like i over here.

I don't think our petrol is inferior to that elsewhere in the world, though until recent years I believe our diesel used to be somewhat inferior to European diesel and caused grief with some high-end Euro diesel cars here.

Another New Zealander here with the same car and the same engine who also became similarly concerned when I read the comments on the NZ AA website.

In my experience (and my own opinion), running BP Ultimate 98 RON for 3 consecutive tank fulls in the car made the engine less smooth overall -- rougher acceleration, rougher idle, rumbling when cruising along at 50km/h at low RPM (Auto transmission), 10% worse mileage (all 3 tank fulls), in fact, I felt that the engine actually ran better on that initial fill of BP Regular 91 RON (when I first got the car) strangely enough!

Switched to using Caltex Techron Premium and Z ZX Premium (Both 95 RON) and the engine performed much more smoothly overall and this is what I've been filling the tank up with ever since I got the car almost a year ago. Haven't noticed any problems (yet), engine is still running smoothly. As far as I've been able to decipher, 95 is the recommended RON for this engine.

The fact is though, more and more of these gasoline direct injection motors are appearing on the NZ market such as SkyActiv, Ecoboost, SIDI. I've known 3 other people who drive the NZ New 2003-2008 Avensis wagons with the same 1AZ-FSE D4 engine and they have put about 200,000km on the car and said they were unaware of such problems.

Not sure if anyone has any experience with this, but there are comments around the place that spraying some Upper engine cleaner every now and again through the air intake, might be able to reduce (but not eliminate of course) the carbon build up enough so that it doesn't cause a problem?

I did get a bit worried when idle suddenly became quite rumbly but have concluded that it only happens from time to time when the aircon compressor is running - as if the computer isn't asking for quite enough power from engine and it is labouring a little as a result. Haven't been able to tie that down to a particular fuel being in use. I will try to be a bit more systematic about observing engine behaviour and fuel economy and report back if I can see a real pattern. I get the feeling that even within brands you can get quite a lot of variation in quality from different outlets at different times, if so that doesn't make it any easier to be scientific about it.

All cars get carbon build up on their throttle bodies, it is because of the exhaust gas reciculator valve and the usage of the crank case vapour in the combustion chamber. The throttle body connects the air filter line(tube) to the inlet manifold. But attached to this is a rebreather that introduces the crank case gases to the inlet. The carbon collects around the circumfrance of the throttle body, when you take the inlet pipe off it might look clean and nice, but take the throttle body off completely and look at from the back, you should be able to see light between the housing and the butterfly valve. When this is clogged up the ideling is affected because the ECU has to open and close the vale continously to allow the engine to breath. The job is simple to do, just need the right tools and some throttle body cleaner, carb cleaner is to aggresive. When the piece is removed beware, you will lose some coolant, yes the engine has coolant flowing through the throttle body, it is to keep the ideling smooth and the metal at a constant temprature. After you have cleaned and replaced the throttle body the ideling wil be high, around 2200 rpm, dont take the car to the shop saying it is busted, the ECU will addapt the ideling to the new flow of air, the engine can breathe again. Drive it around for a couple of hours and repeat the next day, the computer needs both hot and cold readings to reset its fueling. If however after three days it still runs like a meth head, take it to the shop and tell them what was done to the car. The ECU might just need some direction. I am sure that somewhere on youtube is video detailing how do all this. I did it because my car was heavy on fuel and idled like a pig. REMEMBER NOT TO STICK YOUR FINGERS IN THE THROTTLE BODY UNLESS IT IS DISCONNECTED FROM THE ELETRONICS, YOU WILL LOSE YOUR DIGETS.

The problem with D-4 is real. I have experienced the same issues trying to fix they get complicated until replacement of the engine. Carbon build up, excess fuel consumption, lack of power, stalling when accelerating are rampant. So the way to go is to fix new engine the sooner. The more you try to work on the engine, the troubles keeps shifting from fuel rail to ignition errors.

It depends on the location/territory/country and the grade of fuel available. Also notice the measuring standards. Same goes for the ZZ series and the later ZR series which replaced the AZ and ZZ engines when the T27/T270 cars and other models that were updated.

I have a 2007 avensis 1azfse had a 2005 2azfse when was younger and ive heard horror storys a issues about the avensis. Mainly the earlyer ones. Head studs lifting head gaskets trans issues etc. The 2.4 have oil usage issues to do with the pistion rings the 2.0 is pretty good and do high ks without to much problems as long as maintain. When i first got mine i cleaned the egr valve cleaned carbon build up in throttl body cleaned air flow meter serviced trans irdium plugs etc and ive had zero issues. I do run a bottle of cat/egr cleaner in gas tank every 20.000ks but there pretty bullet proof! Had couple of mates who have got 400.00ks out of a moter in 2 of theres! Also DONT RUN GULL 98 the added **** to the 98 frys the lines injectors etc can run Mobil 98 and bp98 as far as i know

the problem is, as it seems, that the engine is running rich, which results in significant carbon build up on the spark plugs, and in the tail pipe. also, in the last 6 months the car has had a noticeable drop in power, accelerating is much more difficult, and often the car will stutter/***** once or twice while accelerating and then the jerking will disappear (although i'm not sure if this is related to the car running rich).

i have also monitored the output of the 4 oxygen sensors, and the first two (banks 1 & 2, sensor 1) seem to be working fine, with sinusoidal variation in voltage ranging from just under 0.1V to just above 0.8V, which is in accordance with the toyota service manual.

i will test the other two tomorrow (the post-cat ones), since their output is more specific, and the toyota recommended test is a bit more lengthly, but based on first impression, the seem to be functioning normal as well. besides, from what i understand, they have no role in the regulation of A/F mixture?!?!

i have also tried disconnecting the MAF sensor, and except for the error codes for the missing sensor there was no noticeable difference in the way the engine ran...i'm not sure what to make of this????

p.s. immediately after starting the car there is a brief period where smell of gasoline fumes that seem to be coming from the engine can be smelled, and i'm under growing suspicion that the catalytic converter may be clogged, although as i have mentioned, the ECU doesn't show any fault codes.

One covering poor drivabilty when cold including engine jerking, which requires a reprogramming of the engine ECU to alter injection timing and knock control ( can affect all pre 2006 facelift 2.0 models )

I run a 1.8 2001 vvti gs. I have exactly the same symptoms except I found that my injector 1 and 2 are leaking. I have sourced some from a breakers and I ll let you know how i get on. my fuel trim went up to 0.9 and fluctuated between 0.3-0.9. I am pretty sure thats high. However, I think before any damage can be done if it can not lean a rich condition it ll come up with error bank 1 too rich or bank 2 too rich and put the car in limp mode and to come out of which you only need to restart the car. I think you should start off with a cheap fix i.e. change your air filter and then look at other bits.

Well, as Devon was kind enough to inform me about a couple of service bulletins, one of which concerns the fuel system (fuel pipe and parts from the fuel pump) i took the car to the dealer today and made an appointment for a checkup Friday morning.

According to the bulletin, they are supposed to replace the concerned parts, although this won't happen, since they never get tired of trying to play me for a fool. I'm never buying toyota again because of the local dealer.

Check your power supply as well please. Also I want to tell you that if your injectors are not leaking but slightly clogged up, this will definitely effect spray pattern and will cause the car to run rich as inefficient burning would cause more fuel to be injected and sensors go a bit silly trying to adjust fuel trim between lean and rich lean and rich lean and rich ... if you catch my drift.

personally i wouldnt think that you have leaking injectors from what you are describing as overly rich causes massively crappy idle. If thats not the case, enjoy it and treat it to something like bg44k.

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