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Surging / hesitation at 2100rpm (and it’s killing me!!!).

I had exactly the same problem , changed plugs, coils, filters , catalytic converters and still the same surging. I found the problem, carbon build up around the valve seat. I valve bounced it and the car ran perfect for alittle while than started surging only slightly. I used fuel and oil additives to clean carbon build up . Fixed the problem, car run like new
 
HI folks
I can tell that MY LC120 (173HP manual gear) has always had low performance around 2100-2200 RPM (it is like this since I have it, 145k Kms, now it has 243k kms).
having studied symptoms and researched i am suspecting it should be solved by TNF52/12 fix... but no luck in getting it done here in Italy
 
TNF52/12 fix?
this seems to be a TNF52/12 ECU Update. I dont know anything about car mechanics but out of curiosity looked at this in google and there seems to be many prados that had staling, hesitation issues and this ECU update seemed to solve the issue.
 
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this seems to be a TNF52/12 ECU Update. I dont know anything about car mechanics but out of curiosity looked at this in google and there seems to be many prados that had staling, hesitation issues and this ECU update seemed to solve the issue.

Ah I see... bloody computers again
 
AussieArthur who started this thread eventually solved his with a new maf sensor, after months of pizzing about and with poor input from Toyota and a lot of expense, thanks to TONYC11.
Read from page 1, result on page 2.
 
SURGING FINALLY SOLVED!!!!!

After getting to the point of having very few remaining options, and convincing myself it was an ECU issue - I went back through the listing of ECU inputs that I found in the schematic below (I included the full extract in a previous post).

Using Techstream I re-checked that each of these items was providing stable inputs and reasonably relevant measurements. Except I couldn’t test crank angle or cylinder recognition - largely assumed these to be fairly major inputs that would definitely throw multiple codes and would cause more significant symptoms.

View attachment 322941

All the readings seemed spot on. And I was really only left with the intake airflow. Readings from the sensor have been hard to monitor properly as there is constant fluctuations. I’d previously discounted this sensor because it gets cleaned frequently and I guess the logic had been that if the sensor was faulty, then the car would have problems running across all rev ranges.

So as a last resort I tracked a second hand MAF sensor down from the wreckers ($50) and plugged it in.

BLOODY STOKED!! Car now runs perfectly.

TONYC11 - from the uk forum nailed it with his inputs. Bloody genius who gave me the push I needed to go back over these inputs and to not discount the MAF sensor.

@Fry1988 - really glad you got the solve on this one too. Does somewhat show that the MAF can still largely function, albeit with dead bands that affect specific rpm ranges. Mine was cleaned frequently, but just no longer functioning in specific ranges.

And - a really big thanks to everyone else on the site who chimed in in this thread to help - particularly @Tractionman @karl2000 , to name a few.
SURGING FINALLY SOLVED!!!!!

After getting to the point of having very few remaining options, and convincing myself it was an ECU issue - I went back through the listing of ECU inputs that I found in the schematic below (I included the full extract in a previous post).

Using Techstream I re-checked that each of these items was providing stable inputs and reasonably relevant measurements. Except I couldn’t test crank angle or cylinder recognition - largely assumed these to be fairly major inputs that would definitely throw multiple codes and would cause more significant symptoms.

View attachment 322941

All the readings seemed spot on. And I was really only left with the intake airflow. Readings from the sensor have been hard to monitor properly as there is constant fluctuations. I’d previously discounted this sensor because it gets cleaned frequently and I guess the logic had been that if the sensor was faulty, then the car would have problems running across all rev ranges.

So as a last resort I tracked a second hand MAF sensor down from the wreckers ($50) and plugged it in.

BLOODY STOKED!! Car now runs perfectly.

TONYC11 - from the uk forum nailed it with his inputs. Bloody genius who gave me the push I needed to go back over these inputs and to not discount the MAF sensor.

@Fry1988 - really glad you got the solve on this one too. Does somewhat show that the MAF can still largely function, albeit with dead bands that affect specific rpm ranges. Mine was cleaned frequently, but just no longer functioning in specific ranges.

And - a really big thanks to everyone else on the site who chimed in in this thread to help - particularly @Tractionman @karl2000 , to name a few.
Thanks to this thread initiated by AussiArthur and to others who have contributed I was able to resolve SAME problem with my Prado (50th anniversary 3400 V6 petrol, manual) that had become increasingly sluggish and had an annoying and mystifying shudder at around 1900 rpm when under load. With my patient local mechanic who has serviced the car since new (now has 314000 km) we cleaned injectors, replaced plugs & coils, de-clogged exhaust without much improvement and without getting rid of the 1900rpm shudders. After reading this thread, we thought we’d try replacing MAF sensor as we were running out of potential solutions.

BINGO!!

This 22 year old car now chews up hills that had become hard slogs. It can breathe freely again!!
Like AussieArthur, I’m BLOODY STOKED!!!
Many thanks to you all
 
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