Strange hesitation on 1SZ-FE

[Astronaut]

Disconnected the MAF cable (and IAT) and drove for a while (10-15km) without them - I did not notice a noticeable difference in the engine behavior, just as I did not receive any "check engine" errors

[Astronaut]

Disconnected Battery (ECU reset) and again driven 10-15 km with MAF+IAT cable taken off. 
No "check engine" lights. Zero errors via OBD2.  How it is possible?

[Astronaut]

Let's continue my blog))
I haven't changed the ECU yet (waiting for soldering iron for eeprom), but once again I did a ECU "reset" by removing the Battery for a while.

For the first 15-20 minutes, the car drives normally and there are no hesitations, but then, when the brains "learned", hesitations are appear again.

[flash22]

intermittent MAF/IAT, aftermarket MAFs can be wildly out of tolerance, remove the plug and make sure the pins haven't spread apart give them a good clean with a contact cleaner spray

[Astronaut]

17 hours ago, flash22 said:

ftermarket MAFs can be wildly out of tolerance,

As I mentioned above, I think I have the factory MAF,  and data from it seems to be adequate (from 1 to 30 g/s). + normally responds according to throttle opening.

The IAT shows a little more than it actually is, but I also found a lot of information that on many cars the IAT can show +5...+10C from the actual temperature, due to heat from the engine.

The only thing I'm interested in - is when I remove the socket on a warm running engine, does the engine have to stop immediately?

Because my engine makes a short "stutter" like seems to be about to stall, but then it quickly levels off and continues to run. Do you think this is normal?

[Astronaut]

18 hours ago, flash22 said:

intermittent MAF/IAT

and quite low RPM on idle also can be cause if bad MAF? 
I have 590-600 RPM on 1sz-fe, but normal are 640-650?

[flash22]

did you take off the idle control valve from the TB to clean it?

[Astronaut]

3 hours ago, flash22 said:

did you take off the idle control valve from the TB to clean it?

Yes, cleaned everything from the first days - IACV, throttle body, PCV, vapor solenoid etc.

[Astronaut]

With a decrease in weather temperatures, the symptoms intensified.

when actively moving from a stop sign, traffic lights, the engine almost does not respond to pressing the gas pedal for 1-2 seconds, then we have few jerks, and after that the revs pick up sharply and after 1600-1800 the engine is going, as it should be.

 

 

spent another couple of hours looking for information on various forums.

the main reasons for someone who solved a similar problem - there was clogging of the fuel system and MAF,
MAF which gave data, but not those that correspond to reality.
for example, 3.4 g/s enters the engine, but the MAF shows 2.5 g/s to the ECU.

if  I can imagine something similar with the MAF, 
then with the fuel system... it is not very clear - if the fuel filter is clogged, or the fuel pump is weak - why does the car drive quite dynamically at 2000-7000 RPMs?

[Astronaut]

oh, and I forgot to add - if  I press the gas very smoothly, then nothing strange is noticeable at all,
the engine picks up RPMs normally, and the car speeds up without any problems, zero hesitations.

[flash22]

undo the fuel cap and see if it still does it

[Astronaut]

17 hours ago, flash22 said:

undo the fuel cap and see if it still does it

still does(

[flash22]

Replace the TPS

[Astronaut]

38 minutes ago, flash22 said:

Replace the TPS

But when engine is cold, there is no symptoms, only on warm.

 

[Astronaut]

Whole throttle body was changed (with TPS and IACV). 

During the replacement, the Battery was disconnected (ECU reset).

There were no symptoms for the first 10-15 km.Then everything went back. So - zero changes. When the gas pressed sharply - the engine chokes and wants to stall (600->1500 RPM), but after 1-2 seconds - revs up sharply and everything work normally.

[flash22]

that is classic OCV getting stuck it may be fine when cold but out of spec when hot

[Astronaut]

23 hours ago, flash22 said:

that is classic OCV getting stuck it may be fine when cold but out of spec when hot

I took it out and checked it - it clicked when applying 12 volts, and it was also perfectly clean (just in engine oil), it also runs freely and without obstacles during a manual-mechanical (screwdriver) test. + It has normal resistance in Omh

[Astronaut]

ECU (from 1.3 (but the "same" 89661-0D211)) was replaced (+ immo-eeprom resoldering).

35km was done today - no hesitations, the car is unrecognizable, out of habit - I even squealed with the tyres at traffic lights a couple of times))

let's watch further..

[Astronaut]

+50 km, zero hesitations. Сar starts instantly, and I also noticed an increase in power at all revs, now I have a feeling that I am not driving on 1.0L, but at least 1.3 :)). +the average fuel consumption in the city (according to the the dashboard) - decreased from 8.0L to 7.2L

[Astronaut]

+200km, runs great. So it was ECU (incorrect software probably). it is surprising that 2 previous owners for 160,000 km were fine with all this.

The repair, together with the purchase of unnecessary things, cost about $50. Thanx to everybody for the help.