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

Only because I have had a weird problem that didn't make sense. I took the fuel tank out and on the pickup filter there was a jelly like substance with wings coming off it. As I would pull up to wait at traffic the engine would go into limp mode and of what I could see the small area that wasn't covered in jelly would get one of the jelly wings stuck to it and block the pickup slightly.
Apparently this diesel jelly substance is common , I'd never heard of it before but 3 mechanics I know knew about it and the guy up the street from me said that his mate worked on planes and said they use an additive in the planes to stop it.
 
Shayne, I see the value of your marine diesel biocide to prevent the 'gunk' forming, but how does it work on 'gunk' already in there. Is it just a preventative in a clean tank, and presumably needs regular dosing ?
 
The bug is a live organism set to multiply , kill it and it will get trapped in your fuel filter as it has been doing for a long time before the problem got severe enough to cause problems .

I reckon its caused by water in refuelling tanks and a reoccurring nightmare for boats hence we order fuel filters 10 at a time .

Wynn's dry fuel turns water in your fuel to jelly which allows a normal filter to trap it .
 
I worked on a Narrow boat some years back that had Diesel Bug.... Inaccessible fuel Tanks Built in to the Frame work didnt help, I had to cut a hole in the side of the Boat To gain Access, The mess inside was shocking as was the Fuel lines and filters....... Strange like Strands of cotton fibre is the only way to describe what was inside the Tank and Lines........ Messy job to say the least... Welded the Hole back up when id done, And job was a good 'un'...... Filling up from Diesel Bowsers doesnt help.......... But in all my years Farming i never Once came across the Problem in Tractors..... But have Known HGV'S with the Problem... :confusion-shrug:
 
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He never came back here or the other forum, after saying it was going to Toyota.
Presume they must have fixed it mate, then removed his wallet !
 
Good evening team - hoping everyone is well!!!

Apologies for the delay, it’s been hectic here in Brisbane the past few weeks.

As expected, the wrestling with Toyota has taken many weeks and to be honest has been rather pointless.
After taking the workshop manager for a 1 hour drive to thoroughly go through the history and surging issues on the road - I thought we might make some progress.
Unfortunately it rained a fair bit, caused some major flooding and the workshop shut for a week or so. I finally got a call nearly two and a half weeks later to say that they’d managed to get a code (small surprise since it hasn’t thrown a code for the last 12 months). Somehow technician ouldn’t ‘recall’ the code, but was related to fuel primer and filter $390.
Not surprisingly it made no difference at all - very much a case of some unnecessary work, sell some parts and get it out the door.
They also wouldn’t share their Techstream data with me. I had hoped this might be a reasonable request???

So nothing to show from Toyo. And they took a piece of my wallet!!!!
@karl2000 - you nailed it!!!

So…..where to now.
I found a pretty good little technical paper from Denso on the fuel injection system:
https://www.service-engine.com.ua/webroot/pdf/TOYOTA LAND CRUISER (2).PDF

On page two it shows a really handy little schematic of some key inputs that the ECU relies on to make informed decisions about fuel delivery. Couple of screenshots included as well.

After reading this, I am realizing that my troubles are so consistent, easily repeatable and somewhat dependent on specific revs AND a particular load state being achieved i.e uphill - it’s possible that the ECU (or one of these specific inputs) has a role here.

So now off to check each one of these ECU inputs - inspection, clean and where possible some further review on my poor version of techstream.
 

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So now off to check each one of these ECU inputs - inspection, clean and where possible some further review on my poor version of techstream.

Please let us know if you find any clues!

I see you are in Oz - are you anywhere near Fourby4Diesel?
 
So, I finally took my Prado with same/similar issue to Adelaide Hills Toyota Mt Barker. After test driving and some diagnosis, they found rail pressure to be good, MAP sensor good, but the MAF Sensor to be dirty. After cleaning the MAF sensor the issue has appeared to have gone. They charged $75 for their time.
Prior to taking to them, I had replaced the EGR valve, removed and cleaned the Intake manifold, and replaced the MAP sensor filter.
 
Interesting, I've never cleaned mine. Where is it located?
 
In the event of not having the proper gear, as per Karl, I used switch cleaner with a cotton bud.
Not a lot came off mine, so didnt make any difference.
Be very gentle this is a fragile item easily damaged
 
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.

A93FA558-6336-42DF-B741-1C7B86CD5D66.jpeg


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.
 
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