Drivability problem driving me crazy for 1 year

Hi guys,
I have Toyota Avensis Verso 2002 vvti 2.0l engine.
I have changed major parts like all 4 oxygen sensors upstream and downstream, catalytic converter, plugs, coils, throttle body and what have you.

I have passed inspection 2 times straight now with the results below

1st inspection HC: 2 (100), CO: 0.1 (0.5), CO: 2500RPM 0.1 (0.3), Lambda: 1.01 (0.97-1.03)
2nd inspection HC: 42 (200), CO: 0.0 (0.3), CO: 2500RPM 0.0 (0.2), lambda: 1.02 (0.97-1.03)

The engine revs fine with very good compression. Fuel trims look good but I guess may become perfect if I can nail down my drivability issue, and fuel consumption looks perfect...factory says my car should do 32.4MPG and I’m doing 33.62MPG at 8.4l/100km or around 625km for 49 liters of fuel especially after I did wheel balancing and alignment I gained more MPG moving from 560km/49ltrs to 625 or 670km/49ltrs.

My car is very sluggish and feels like it’s doing a heavy job to move and this heats up my catalytic converter thereyby throwing the CAT codes. I cleared the codes and went in for inspection and passed.
I have narrowed down 3 suspects which are MAF, clogged muffler and EVAP vsv, as for the Evap vsv my suspicion on that is because I noticed some pressure when I try to open my gas cap to fuel my tank but when I put the nozzle to fill up my tank it works perfectly fine without me holding the nozzle.

This car I noticed was originally registered in UPPSALA northern coldest part of Sweden and I could see the rust coloration on some part of the car’s body compared to car’s from southern parts. Also when I bought the car it had 4 bad oxygen sensors which I suspect may have affected the exhaust system from CAT, resonator to Muffler. I have changed CAT and I seem convinced that’s not where the problem lies. In the morning when engine is cold I start the engine and I can’t feel much heat of exhaust gas coming out from the tailpipe when I put my hand but after 30mins of driving I could feel feel it.

I need you guys to help me because all the big dealers and workshops here don’t even have a vacuum gauge to use in doing a back pressure test, I have on my own taken out one of the upstream A/F sensor and used my obd2 to check exhaust gas and it passed all tests, but once I plugged in the A/F sensor again it failed.
I have cleaned MAF just as scannerdanner advice me sometime last year I think and so far so good.
STFT bank1: -0.78, +1.56, +3.56 in that Range same for STFTbank2
LTFT bank1: -4.72 almost the same for LTFT bank2. Although I passed inspection but on the two occasions they wrote same remarks that OBD2 self test not performed, I want to believe this remark means one of the monitors was not completed, correct me if I’m wrong. I have the Chinese Toyota techstream that I have hooked up myself and everything looks fine....all the monitors were completed except CAT monitor, and then EVAP vsv was showing off and when I tried to turn it on with the techstream STFT goes up, so I’m assuming that’s how they engineered that to work for the PCM to turn it off and on itself when needed.
I tried to do volumetric efficiency test....on gear2 at 3000RPM 99.61 engine load, IAT 140 Fahrenheit, MAF 57.23grams/sec
Shouldn’t MAF gets to over 100grams/sec with this test.
Technical manual says my IAT should be the same as ambient temperature. What do they mean by this, temperature reading showing on the car radio inside the car or temperature in the engine bay. It was showing 100 Fahrenheit on the car radio inside the car. At idle my IAT is 138.2 Fahrenheit before the test. Will a higher or lower IAT reading give drivability issues and also make me have a rich condition and could a clogged muffler affect IAT reading and also cause rich condition. I am attaching the A/F sensors readings.
The condensed water flushed out of my tail pipe last year which makes me believe this drivability is the muffler and also why I gave information that the first owner was living in a very snowy northern Sweden where the salt water to clear it must have rusted the internal of the muffler and also bad oxygen sensors may have contributed. The external of the muffler looks good, I have gone under two other cars and it’s same look with my muffler but you could see a big map outside the muffler like water inside showing the map shape outside. The aftermarket muffler is very pricey here with 25% vat, can I drill a hole in the muffler to allow water to escape and back pressure to have some outlet? For over a year I have never seen one droplet of water coming out from my tailpipe which is weird, so water must be gathering somewhere in the muffler.
Cars should be engineered with no inter-dependencies. I need to know if my IAT and MAF readings are good and if a clogged muffler could affect the entire system from oxygen sensors, CAT, MAF etc.

There is a lot in your post so these are just my first reaction, generally if the exhaust is blocked you will feel the difference in the way the engine revs by removing the upstream O2 sensor without the need for a gauge --- an anti-social rough and ready test.

As to the intake air temperature generally the IAT is only the same as the ambient temperature after the car has been parked without the engine running for enough hours for the engine to cool to ambient. Ambient temperature is the outside air temperature. At other times with engine running the iAT reads somewhere between ambient and coolant temperature --- highest at idle rpm.

Thanks Andy for helping me solve the IAT part, you were so spot on.
At cold start my IAT was exactly the same as my ambient temperature and when driving on highway they are also the same, the only time IAT goes higher than ambient temperature is when you slow down or you are parked because natural breeze is not blowing into the engine. Just like you said that was what happened when my IAT was reading 60 degrees Celsius, I was parked at that time and you are also right it should read between ambient and engine temperature.

Thanks for your help.

After thinking it over wondering if it could be a VVTi issue I think that would explain the general lack of power without a major effect on fuel consumption. I don't how much data and which bi-directional tests your scan tool can do on VVTi system ?


That is a very large amount of condensate in the muffler but unless the car is loosing coolant it would not concern me.

I have never had to top up my coolant. I have now yanked off my muffler and the situation is still the same.
I have the resonator as the next point of call, but since the exhaust system is so difficult to work with, I am thinking of making my MAF the next step after the muffler. Some background info on the MAF...after I bought the car scannerdanner gave me suggestions as to cleaning my MAF and after 3 times cleaning I went down in fuel trim from -21 to what I have today.
The car is suffering from hesitation and loss of power, the hesitation is very noticeable on cold start.
Can a clogged exhaust affect MAF performance and reading. When I’m on top speed on the highway, what grams should my MAF be reading considering my engine is 150horsepower.
Can a vacuum leak cause hesitation and loss of power in a rich condition.
Since my MAF is not throwing any codes, could you help me with a 100% fast method of testing my MAF functionality.
KOEO I did my TPS test and got 80% and I think that’s around 4.5v or something. 64%-98% is Toyota factory recommendation.

A figure you can use is at 5000 rpm the MAF sensor should report about 40grams per second for each liter of engine displacement on narurally aspired engines.

A clogged exhaust system will affect the MAF reading. If the exhaust gases can't get out then fresh air can't get in, that easy.

You say the car feels "sluggish " , can you floor the car and measure the acceleration from 0 to 50 or from 0 to 100 km/h?

The thing that is puzzling me is the fuel consumption is okay I drive a car of similar size and engine size perhaps slightly heavier and in mixed urban driving 32mpg is about typical. As the fuel consumption is okay it eliminates mechanical friction from the brakes or other causes. A Volumetric Efficiency test could show something. I am also wondering if the TPS showing 80% is enough throttle opening, you never get 100% but 80% is a bit on the low side.

Rubble from the cat in the muffler would restrict flow but there is no mention of the old cat being being smashed up.

In last year inspection they said one of my back tyres was gripping due to mechanical rust and I have changed my brake drum/pad and I saw them checking all tyres movement on a jack at the inspection I did a week ago and everything passed.
If I have mechanical grip in my tyres, should that affect my CAT?
My CAT is heating up due to lack of air I believe, otherwise if my injectors are dumping excess fuel in the CAT I should have low MPG.
I also believe my TPS and MAF are not loading to full capacity due to the fact the MAF can’t expel air out from the exhaust system.
The reason I’m suspecting my exhaust I’m attaching in the images. I have odb2 WiFi and techstream, but before I created some form of air outlet in my exhaust system by pulling out one of the A/F upstream sensors and now my muffler, my OBD2 exhaust gas sensor results showed failed in 4 out of the 8 tests, but everything passed when I pulled out my A/F upstream sensor, and failed again when I put the sensor back...immediately I yanked my muffler off to release some exhaust back pressure the 8 tests showed passed again.
I will contact OBDCarDoctor to explain to give me more details on the parameters as they were not shown fully for lack of space I guess, or I use my iPad instead to get the full (Exhaust gas sensor bank 1 - sens...)
Atleast I have ruled out it’s not my muffler, money saved.
I’m suspecting creating an outlet for back pressure is enough to make the exhaust pass but then the restriction that affects drivability still lies somewhere in the exhaust system and most like after the CAT and before the Muffler (resonator).
This is exactly the drivability problem I had before changing my CAT, and now I have removed my muffler and still problem persists, that leaves the last culprit in the system which is the resonator or the rest of the exhaust system minus CAT and Muffler.
The first set of attachments will be for the failed 8 tests of the exhaust and the next will be when it passed, if anyone can help me figure out the information and label the parameters properly for me.

These are the passed results and also I’m attaching Toyota engine operating condition.
Although the drivability problem is still there.
For all I know my MAF is not producing what it should be producing in grams at WOT. I read somewhere MAF should give 80% of engine horse power, my engine is 150hp and my MAF should give 120grams/sec but I’m getting far less.

Which is the best and fastest diagnostic route between a MAF and exhaust. Otherwise I go and find someone who can borrow me a MAF because if I buy they won’t accept a return for electrical parts.

Peak torque on your engine is at 4,000 rpm, peak power is 148 at 5,700 RPM to look at volumetric efficiency you should capture the data at 4,000 to 4,400 rpm

I am attaching data for engine load, tps, MAF reading and dashboard when I was on the highway at 90km/h around 60mph
And the next data I am uploading was acquired when I was parked, I rev the engine to around 7000rpm and you can tell me if the tps and MAF readings are correct.

Appreciate your help a lot. The mechanics here don’t do vehicle diagnostics apart from changing ball bearings and stuffs.

TPS and MAF at 7000rpm when in the parking lot.

I suggest you do a test drive and record the relevant parameters with your techstream in graph mode....
I would like to see tps, maf, rpm, engine load, fuel trims.

Have you put a vacuum gauge to the intake in order to confirm a plugged exhaust?
That's pretty straight forward...

Like I said all the dealers and big mechanic workshops here don’t have a back pressure gauge, I’ve been to 8 of them. I am going through a very painful diagnosis myself and I will be very happy once I find the drivability fault.

I have gathered all the data you need but I will be sending first in meter graph. I ordered an aftermarket MAF sensor with 1yr warranty which means I can return it. After installing the new MAF everything remains exactly the same as if I had my old MAF, no changes whatsoever infact my old MAF was showing LTFT around -7, STFT around 2.34, the new MAF LTFT -11, STFT 0.43.

I will attach 4 images.
1. All the parameters at Idle RPM
2. All the parameters at 1500 RPM
3. All the parameters at 2500 RPM
4. The specific data you requested at meter graph mode captured at 4437RPM. I will try and send you the line graph mode later.
My next message will be about what I found out doing an active test of injector volume and A/F control injector volume using the techstream. Could you pls help me and look into calibration update, I have this number showing on the techstream for engine and ECT 34404100. Otherwise I find someone with an OEM MAF to borrow.
Thanks for your time.

As for the injector volume test and A/F control , the results didn’t match techstream expected results.
I did test for IAC duty, purge VSV and VVT control (bank 1) and they all came out fine with the expected results specified on techstream.

But when I did injector volume test, at 3000RPM it just permanently stayed at -0.04% instead of switching from 24.72% to -12.5% incrementally and same thing happened when I did A/F control test the injector volume remained at -0.04% permanently instead of switching instantly from 25% to -12.5%. Can this affect TPS and MAF reading output, since I believe my TPS at full torque of 4400RPM should have read 80% as against the 38% I got and MAF should be around 120grams/sec at same RPM as against 49.01grams/sec I got.

Some more info and also little clarity needed. I did not shake the old CAT to know if it had any rustling sound of broken pieces that would have gone into the exhaust system, I was a total novice in that. I’ve thrown that CAT away.
Before taking off the muffler, I passed inspection but then with a comment that onboard diagnosis system self test not performed and it seems it’s because the CAT monitor was incomplete or failed. The CAT monitor has been failing for more than a year and it took me just 2 drive cycle to make it pass now after muffler removal.
After I took of the muffler, techstream is showing all monitors are complete and passed but of course i’m still having loss of power.
As I was watching the live data, of course my wideband A/F upstream sensors is still out of stoichiometry with low voltage of around 3.24v instead of 3.3v (running rich).
My question is on my downstream sensor, since CAT monitor passed the downstream o2 sensors have stable voltages of 0.7-0.8v for a minute or so and immediately just drop to 0.035 when radiator fans kick in and back to normal again within 3-5 seconds.
Will a rich condition affect voltage readings of downstream sensors also even though the job of the downstream sensor is to monitor the efficiency of the CAT which it has done successfully but still drops in voltage. Is the behavior of my downstream o2 sensor normal considering all the information I’ve given out so far. I’m just trying to separate facts from fiction. All the big mechanic workshops here claimed car is fine when infact it’s not considering -11 LTFT and my driveability problems. This is a rogue operation for me, one shop even quoted me new CAT and new ECU. Atleast now I know I can’t trust their words since my CAT monitor has passed.
CAT monitor....completed and passed
O2 sensor monitor....completed and passed
O2 sensor heater monitor..,,completed and passed

Can someone tell me if my problem is on the Air side or Fuel side or both so I can streamline this diagnosis. Is this a calibration problem I need to perform after changing my CAT, where can I find TSB for this car.
Which is the best method to eliminate 100% a downstream 02 sensor problem. I’m totally not concerned about the upstream sensors as they are brand new OEM from Toyota dealership. The downstream were bought used at 60,000km.

Once again I ask you to record a test drive under varying driving conditions and post this techstream file here so anyone can open it with techsstream to analyze the data.
The pictures you posted are very limited and there is no under load data.
Did you ever do the volumetric efficiency test Andy suggested?

It would help us if you took screen shotds.

How to take screenshots in Windows

www.howtogeek.com/226280/how-to-take-screenshots-in-windows-10/

getgreenshot.org/

Thanks Andy, Screenshots would be very perfect as anyone without techstream can view what’s happening. I will take as many interval screenshots under varying conditions and load from gear 1 to gear 5 (20km-90km).
I understand an expert can use my fuel trims information and behavior to diagnose the problem also.
I have now taken away my resonator and muffler and nothing has changed. I still have loss of power.

My long term fuel trims on both banks remain around -11 (negative 11) at idle, but when I’m on the highway with my leg fully on the gas pedal, my LTFT drops to -1.56 and once I take my leg off the gas pedal it goes back to -11. STFT remains 0.78 - 1.56 on both banks.
This behavior in a STFT would mean vacuum leak I guess, but for a LTFT to drop under load can anyone make out what’s happening.

Andy from this thread below mirroring the same problem I’m experiencing you mentioned that o2 sensor may be lying. I am tilting towards my downstream o2 sensors because they are the ones I bought used and I remember after watching a video on YouTube having negative LTFT due to downstream sensors switched to the other, I switched my downstream connector cables and there was so much white smoke coming from the exhaust like raw fuel getting into the exhaust or something, but funny thing is on gear 1 at some point in my test drive the car was flying like it just came out of the factory, like something blocking the throat just suddenly release, unfortunately CEL P0420 and P0430 came on again. I had to switch the connectors back. I will do a swap of my downstream sensors by taking the sensors out and not just the connectors swap and see what happens. I bought an oxygen sensor FROM a 2003 Verso with same part number at 60,000km, now I’m wondering how can a 2003 car have 60,000km (km and not mile), then it probably means the sensors have been replaced and nobody knows if the replacements were OEM or aftermarket. I bought the sensor in 2017 and that means it came from a 14yr old car, even if the car did 10,000km/year that’s 140,000km in 14yrs. We do an average of 15,000-25,000km/year here.
I’m willing to take this up with the part dealer and file a report if they can’t be honest enough to display right part history.
After going through one of the old threads on this forum, I am beginning to be more than convinced I need an OEM MAF sensor, simply because my first fix on my car to drive down my STFT from +25 to what I have today was cleaning the MAF sensor, I am of the opinion cleaning of MAF sensor works maybe 50% of the time. My MAF reading is acting funny under load in the parking or while driving, sometimes 54g/sec at WOT and sometimes 92g/sec. my MAF should read above 120grams/sec even though it checked out fine at idle and under load without driving following Toyota technical information, but Toyota didn’t go further to tell us how the MAF should behave under load on the highway. Most likely the aftermarket MAF I installed did not do a better job also. I have seen far too many internet posts of problems with fuel trims with people throwing in other parts and at the end the fix was an OEM MAF, even some people ran into problems using aftermarket MAF.
If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. A faulty MAF can give high negative or positive LTFT I suppose.

www.scannerdanner.com/forum/post-your-re...-codes.html?start=17

www.scannerdanner.com/forum/post-your-re...ve-ltft-at-idle.html

You might want to try to disconnect the 2 precat A/F sensors or even better the 2 postcard oxygen sensors as well.

That way both banks will stay open loop and fuel control would not be skewed by misreporting sensors.