Car Engine (1Az-Fse) Running Rich On Fuel

[Vlado P.]

hello,

i have been having this problem with my avensis for a while, but have finally decided to find the cause and hopefully fix it....

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 scanned the ECU for error codes, and no faults are detected. the car engine is running smoothly, there are no vibrations in the cabin or under the hood.

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?!?!

fuel trim is also within +- 10%.

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????

since everything i have tried so far appears to be normal, i'm slowly running out of ideas where to look for the problem.

i would greatly appreciate any ideas as to how to solve my problem!

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.

[Devon Aygo]

PM your chassis number as there are two bulletins from Toyota:

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 )

The other a recall surrounding a pipe and valve on the hight pressure fuel pump which can result in a fuel leak.

[Vlado P.]

chassis number sent by PM...

thanks!

[waqar_lionheart]

Hi,

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.

also try and put some fuel treatment in a run the car, these things work magic (sometimes :) )

regards,

waqar

[Vlado P.]

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.

Back to the topic, i'll wait and see what will happen Friday morning, and then decide further.

I am sure that even if they replace the parts, this won't restore the power, and make the car run leaner.

I can replace the air filter, however a month ago i tried driving the car without air filter, and there was no noticeable difference in performance.

Just out of curiosity, how did you determine which injectors were leaking?

[waqar_lionheart]

mine were a bit more obvious than other people. These were leaking internally and petrol oozing out of power supply.

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.

Regards,

Waqar

[Konrad C]

Remember the 2.0l vvti has direct injection, so any issues with them will be a little different to the 1.8 vvti. The 2.0 vvti has higher pressures.

When Toyota put their diagnostic on the car (like techstream), they could see why the car is not running properly. I know diagnostics have been done, but Toyota should be thorough.

Hope all turns out well.

[Vlado P.]

i would try bg44k, however it's not available where i live, and it seems it is going to be difficult to find someone who will ship it, as well.

in the meantime i ordered one of those chinese clones of mongoose diagnostic cable, comes with techstream, so as soon as it arrives i will try and extract some more useful data, then is currently possible with the OBDII scanner. it will probably take more than a month to arrive though...

i will ask friday morning if they are willing to do a more extensive diagnostic on the fuel system, although i highly doubt it, considering my past experiences with their diagnostic practices.

[Vlado P.]

well, i took my car to the dealer's today, they had a quick look and according to some internal documentation came up with the stance that only the fuel pipe is eligible for replacement. allegedly, they had this confirmed with toyota as well. i remain suspicious!

anyways, the pipe is to be ordered from toyota and sometime early september i should be contacted to bring the car in for the pipe replacement. we will see if this will eliminate the gasoline odor coming from under the hood.

in the meantime i ordered a bottle of redline SI-1 from eBay (since i wasn't able to get bg44k for a reasonable price), and as soon as the pipe is replaced i will pour the SI-1 in the tank, and see whether there will be some sort of improvement. based on what my sparks look like, i'm sure there is a lot of carbon build up in the cylinders. does anyone know whether redline SI-1 is supposed to clean the cat converter too?

[Pauljah]

Vlado P, when I read your problems with this engine I thought you were describing my car. Just today I visited a repair shop and the mechanic feels sure my injectors need to be replaced. These things aren't cheap so I would really like more confirmation before spending big bucks---any thoughts here?

[Vlado P.]

well, i took the car for a service last weekend, and they had the fuel pipe replaced as declared in the bulletin. this turned out to be a small serpentine-like pipe, feeding the fuel pump with gasoline. this does not seem to make any difference (and i wasn't expecting it would), but at least i have some peace of mind that the pipe wont burst on the road.

immediately after, i poured a bottle of redline SI-1 (which was quite difficult to obtain) and filled the car with a little more than 3/5th of the tank (i didn't want to dilute the redline too much by filling the car to the top). it might be subjective, or it might be coincidence but the car seems to be running better and has more power, and i haven't even driven 20-30 km. as soon as i use up all of the gasoline in the tank i will remove 1-2 spark plugs and see if the redline additive has managed to remove some carbon from them.

i was kinda hoping to scan the car and perform some techstream tests, however the cable i received is not working so i will be requesting a replacement. this will take another month or so :((

Pauljah, i am quite skeptical that your injectors need replacing. i haven't heard of a case where all four injectors went bad at the same time. if your car has lost power you might try checking the catalytic converter, it might be getting clogged. i am planning to do the same, although i don't think i will find anyone qualified in my area so i will have to improvise something...

[frankie406]

Have you checked your evap/canister?

[Pete W]

Mine's the same, and it's been a bit iffy since i bought it in 2004. Have had the recalls from Toyota with no difference. Scan came up with 02 sensors, so i changed all 4, no difference. Then came up with throttle body, so had that cleaned, no difference. Disconnected Battery to reset, no difference. then it came up with cat no working properly, but with these having twin cats, i couldn't afford to change them, so have basicilly left it. Just clocked up 230,000 miles, and it still pulls ok, apart from the odd seemingly missfire. What can you check on the evap/ canister, not tried that yet.

[Vlado P.]

nope, haven't checked the evap canister yet, but i'm primarily concerned by the car running rich...or so it seems. it could be normal for this type of engine, but first i want to perform all available techstream tests. if i can get a cable that works...

[frankie406]

Have you cleaned the maf sensor with cleaner for it?and is it proper spark plugs your using?

[Vlado P.]

cleaning the MAF sensor is planned, however i still haven't cleaned it since i can't find a cleaner. apparently, those cleaners that were previously available aren't allowed to be imported any more, something to do with containing substances banned by our ministry of environmental protection.

the spark plugs are the factory ones, so they are original

[frankie406]

When did you replace your plugs?

[syncview]

Can you tell us LTFT and STFT values?

have you received your toyota cable yet?

if you have a generic OBDII scanner that would show you lots of data including LTFT and STFT values..

to the guy having problems with the injectors: don't you have access to an ultrasonic injector cleaning facility, most of the time it ends up really cheap and you have like-new injectors.

[Vlado P.]

i haven't replaced the plugs at all, however the car has only 73000 km and they are supposed to be good up to 100000 km.

last time i scanned (about a month ago) short and long term fuel trim values were in the range +- 4%. as far as i know anything up to 10% is normal???

in what solvent do they clean the injectors?

[syncview]

Remove a plug and check it's condition

Check the current fuel trim values that you have a problem now

[Pauljah]

Can you tell us LTFT and STFT values?

have you received your toyota cable yet?

if you have a generic OBDII scanner that would show you lots of data including LTFT and STFT values..

to the guy having problems with the injectors: don't you have access to an ultrasonic injector cleaning facility, most of the time it ends up really cheap and you have like-new injectors.

[Pauljah]

No there is no ultrasonic injector machines here. I am buying new ones snf plan to also clean the cat converter. My rav is a Japanese edition with only 1 cat converter.

[Vlado P.]

ok, after some changes in the situation it is time to update the topic...

as i previously mentioned i had used a bottle of redline SI-1, and this product definitely cleaned something, since after using up the tank of gas, i removed a couple of the spark plugs and the main electrode was now clean. the rest of the spark plug was still fouled in carbon build-up, but at least one of the three electrodes was clean (i'm guessing because it was most exposed to the redline fumes). this lead me to believe that redline did clean my injectors, if there was anything to clean.

in the meantime i also received a working techstream cable, so i had the car scanned and no faults showed up. i had performed several of the active tests available in the software, and from what i can tell, everything seems to be working normal. there is even a catalyst efficiency test, and the test passed with flying colors (the numbers were far from the threshold values). i'm not sure whether these numbers relate to the catalysts being clogged up or not, but it seems that the cats are working fine as well.

i still haven't cleaned the MAF, but the good news is that after a long search i did find and order a can of CRC cleaner, so this will be done as soon as the cleaner arrives.

one thing did turn up for the WORSE though! namely, these problems i have had with the car stuttering once or twice when cold, have exacerbated, into a different symptom.

namely, now when the car is not cold, but not properly warmed up either (half warm), the car stutters, jerks and completely loses power if i step harder on the pedal. it is as if it's choking, until the engine reaches higher rpm (>2500), after which it will suddenly pull like rocket. if i drive the car i higher rpm, this problem is not noticeable as much, but the lack of power can still be felt.

while idling (~800 rpm), if i floor the gas pedal the car first stutters/chokes a bit (and shaking from the engine can be felt all over the car), then revs up with no problem. if i press the pedal gently, then the car revs up without this choking and there are no vibrations. when the car is cold (idling at 1600-1800 rpm), and when it has properly warmed up these problems are not present.

somebody suggested that there might be a faulty temperature sensor???, although i'm doubtful, since the temp indicator works the same as it always has. but what can cause a problem when the car is half-warm???

couple weeks ago the car did flash a check engine light (scanning revealed error from the B2S2 oxygen sensor), but this error disappeared immediately after unplugging and plugging of the sensor connector. i'm thinking this was something to do with oxidation of the contacts or moisture in the air due to the winter. i have scanned several times since, and the error has not reappeared!

to be honest, i don't have any more ideas what could be the problem. i will definitely clean the MAF, i was also thinking of changing the spark plugs with Iridium tough VKB20, but i don't think that the plugs are the problem, and everybody i have spoken to, also thinks that the plugs are not the culprit.

i am open to any constructive suggestions, since this is really starting to be a problem.

regards,

vlado

[syncview]

sorry i haven't followed this thread

but have you checked if the fuel pressure is OK?

can you show us picture of the spark plugs

[Vlado P.]

the fuel pressure seems to be OK - 8 MPa according to techstream, and varies from 6-10 MPa when using the active test function for fuel pressure.

i don't have a picture of the spark plugs, but their bottom face is all carbon fouled