Gerabox A750F taking long time to change gear

[JOMATA Lurker Find all posts View Profile Close JOMATA]

Hello, new here, from Dili, East Timor

I own an australian market 2009 KDJ120R, 1KD-FTV turbo diesel engine, A750F gear box. 153,000 Km.

3 Years ago I changed the gearbox fluid using a gearbox fluid changing machine. It used almost 20 litres of Toyota ATF fluid. the old fluid was dark but didn't seem too bad.

Begining of this year, engine started blowing oil from the back of the valve cover. The mechanics here in Timor declared that it was worn out piston rings. However, there was no blue smoke coming out of the tail pipe, only black smoke in heavy acceleration.

Sudenlly, I started hearing a loud whining when accelerating, loos of power noticeable on hill climbing and gearshifting at higher RPM. Until the car sudenlly went into limp mode.

Ordered genuine new Turbo and new injectors from abroad, installed everything, with my newly acquired scanner cleared all errors and inputed the compensation codes and all seemed fine.

But not really.

Engine starts normally, no more black smoke at all even when trying to accelerate hard, but RPM are slugish to increase and gearshifting, even on a flat road, happens at 2400rpm or above, if pressing the accelerator up to 3200RPM and takes forever.

Scanner shows no DTC in any system.

What could be causing:
1. Slow revving up? Engines seems lacking torque.
2. Slugish gearshifitng? Need ATF changing and gearbox filter cleaning?
3. Could it be any problem with the Transmission Range Sensor although not showing in the scanner?

Any help is most welcome

Best
Joćo Tavares

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Hi Joćo,

The A750 Gearbox manual says that a shift point too high or low fault/poor acceleration can be caused by in order of likelihood poor operation of the SLT Solenoid, SL1 Solenoid or Valve body assembly. The SLT solenoid operation is linked to various engine sensor readings like the intake air volume, throttle position and vehicle speed etc so if you have your foot down due to lack of power it will hold gears.

But I would start with seeing what is causing the engine lack of power first before looking at the gearbox (other than confirming you trans fluid levels are still OK).

Simple things which cause Lack of Power but not throw a code can be checked like:

• Air cleaner is clean and no blockages or air leaks in inlet hoses etc.
• Clean MAF Sensor and clean or replace MAP Sensor filter (It would be worth taking a reading with your Scantool of what your MAF and MAP readings are and compare pre and post clean to see if there is a difference).
  • MAF Normal reading Idling: 5 to 12 g/sec. Running without load (2000 rpm): 15 to 35 g/sec.
  • MAP Normal reading Idling: 94 to 104 kPa (depending on barometric pressure) Engine running at 3000 rpm: 100 to 150 kPa)
• Check the target and actual fuel pressure and SCV readings
  • Target 30000 to 160000 kPa when engine running
  • Actual Idling: 30000 to 40000 kPa (close to target value)
  • Target Pump SCV Current Idling: 923 to 1123 mA
• Check you don't have clogged catalytic converter in the exhaust due to the high soot load when you had the black smoke

These are only a start point but worth checking before you go any further.

[JOMATA Lurker Find all posts View Profile Close JOMATA]

Thank you very much for your very informative response.

I will check those values.

Is there any source of information on what the normal range of values for the sensores readings should on this engine?

I cleaned the MAF with compressed air and used WD40 Contact Cleaner, (no MAF spray cleaner available in Timor). It didn't look too dirty to start with, and now looks like new. Reading is 0,8g/sec engine off and about 14g/sec while on idle.

I'll check the other sensores values against your numbers.

Any "normal values" for the gear box solenoids?

Once again, thank you very much.

Best
Joćo

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

No problems I will try to help with what I can but I make no claims to being an expert and hopefully some of the more experience guys will correct or add as necessary.

For information sources you can try searching online or Toyota Aust have a service on https://toyotamanuals.com.au/ you can pay for which gives you access to all the required info which can be downloaded or printed to PDF to use as needed. You can buy access by the day/week/month/year (I used the $39 AUD week access to get the info I needed for my Prado).

The MAF readings are marginally higher than specified but I would see if there is anything else wrong before bothering to relook at it.

The gearbox only reports ON/OFF status for the solenoids so you need to connect additional test equipment to see if the pressures are OK so not something easy to do. ( SLT should be OFF when accelerator depressed and ON when accelerator released)

But check that you are seeing the input shaft (NT) speed (should be similar to engine revs), output shaft (SP2) speed (similar to vehicle speed) and both A/T Oil Temps as if these sensors are not working it can cause the Trans ECU to alter shift points or not change into some gears - but should potentially have thrown a code if not working so?.

[JOMATA Lurker Find all posts View Profile Close JOMATA]

Hi PTommo59

Many thanks for your great help.

Guess what, the MAP filter had oil inside had been mounted upside down and it was cracked.

I got a second hand replacement in good conditions while I wait for the new one to arrive (about 1 month).

Meanwhile the scanner readings were as follows:

Simple things which cause Lack of Power but not throw a code can be checked like:

• Air cleaner is clean and no blockages or air leaks in inlet hoses etc.
• Clean MAF Sensor and clean or replace MAP Sensor filter (It would be worth taking a reading with your Scantool of what your MAF and MAP readings are and compare pre and post clean to see if there is a difference).
  • MAF Normal reading Idling: 5 to 12 g/sec. Running without load (2000 rpm): 15 to 35 g/sec.
  • My reading: 8 g/sec idle - 25,5g/Sec at 2000 RPM
  • MAP Normal reading Idling: 94 to 104 kPa (depending on barometric pressure) Engine running at 3000 rpm: 100 to 150 kPa)
  • My reading: 80kPA idle - 83kPA at 3000 RPM
• Check the target and actual fuel pressure and SCV readings
  • Target 30000 to 160000 kPa when engine running
  • Actual Idling: 30000 to 40000 kPa (close to target value)
  • Target Pump SCV Current Idling: 923 to 1123 mA
• My readings:
• Common Rail Pressure Sensor #2 - 32300 - 33800 kPA at Idle
• Fuel Pressure: 2300 - 33800 kPA at Idle
• Target Pump SCV Current Idling: 1246mA

Will revert with the results once I get the car back.

Best regards
Joćo Tavares

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Looks like you have serious issues with the MAP sensor readings as they are way too low and you don't seem to be getting any boost from the turbo (This will definitely cause your loss of power issue).

It could be that the sensor has been damaged by oil or contaminants from the faulty filter or previous install when that was put in backwards or a air leak somewhere in the inlet side.

Check you MAP Sensor reading against the Ambient/Barometric Pressure reading with ignition on. They should be close to the same, if not may be time for a new sensor as well as the filter.

Also see what your Target Booster Pressure/Boost Pressure Deviation/VN Turbo Command and Actual VN Position are doing as you should see the turbo trying to get the MAP reading up to the Target Boost Pressure.

The SCV current is reading high so it could be a bit sticky but if it is still keeping rail pressures close to target not a major issue atm (are you readings above just the two pressure sensors or is one the target?)

[JOMATA Lurker Find all posts View Profile Close JOMATA]

Thank you for your great help.

Yes, it looks like I need a new MAP sensor along with the new filter. Taking care of that as we speak and also will check if all the rubber hoses connecting the various sensors are in good order.

Also see what your Target Booster Pressure/Boost Pressure Deviation/VN Turbo Command and Actual VN Position are doing as you should see the turbo trying to get the MAP reading up to the Target Boost Pressure.

What would be normal readings for these streaming values?

I still feel that the problem lies with the MAP sensor, because after replacing the filter with that used one (although been cleaned with carburator cleaner, the little oil residue was cleaned, the filter was blown with compressed air till dry and it looked in good condition), although the MAP readings only improved marginally, the engine is now performing much better acceleration and gear shifting has improved. Still not as before.

• My readings:
• Common Rail Pressure Sensor #2 - 32300 - 33800 kPA at Idle
• Fuel Pressure: 32300 - 33800 kPA at Idle
• I think common rail pressure and fuel pressure are just different readings of the same sensor, aren't they?
• Target value is 35,000 kPA

What I have noticed as well is that it takes longer to start in the morning and seems like the starter generates higher RPM like if there was no fuel reaching the injectors for 2 or 3 seconds. Then it starts normally..
When engine is hot it starts absolutely normal.
Also a MAP related issue?

Best regards
Joćo

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Shame the MAP sensor can't be just cleaned but I don't think it can so better off with a new one.

The start issue is more likely on the fuel side.

When did you last replace the fuel filters? Seeing as you are already doing a lot of work may be worth replacing the rear and front filters and confirm there are no leaks. Then look at the SCV (I believe if they are only sticky you can clean and refit (some videos online about that). Then retest to see if your fuel pressures are closer to target and the SCV Current comes back to normal range.

[JOMATA Lurker Find all posts View Profile Close JOMATA]

Thank you again. your help has been unvaluable.

The fuel tanks (yes, being an australian market it comes with two tanks), were removed and cleaned two months ago. They were filthy with some black gunk. The fuel sensor and the filter were all cleaned.

The fuel/water separator in the engine bay was replaced 2,000Km ago and was checked when they cleaned the tanks. Seemed to be good.

So thi starting issue, which only started after the turbo and injectors replacement, could it be either some fuel leak in the high pressure fuel lines to the injectors, or, the sticky SCV?

Yes, I've seen a few videos on replacing the SCV. Actually even mentioned that id it is the short SCV it should be replaced by the newer longer SCV.

Not an easy spot to work on that SCV.

Best regards
Joćo

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

OK so filters are out which is good. The only thing people have mentioned is air leaks at the water separator if you don't put seal in correctly or tighten ring properly. But I wouldn't relook at that until the SCV issue is fixed and you are still having problems with cold start.

I'd say the starting issue post injector change is just a coincidence and most likely when the sticky SCV became more noticeable as it would have been masked by the other turbo/injector issues.

I'd say that If your high pressure lines were leaking you would most likely have picked it up visually or got a code due to unable to get to required pressures plus the oil levels in the sump would have been increasing as the leak would be inside the rocker cover and draining into the sump.

Is yours the short version? I did also see the videos say that these are prone to issues and should be swapped out for the newer long version at first opportunity.

Lucky for me haven't had to play in the SCV area as had both of my Hilux and Prado from new and changed over at 9yrs/195K prior to any major problems.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

It might be interesting for you to monitor the Target and Actual Fuel Pressures plus SCV current when you are cold and warm starting to see if there is a difference in how long they take to stabilize and the engine start. If there is a major difference then it most likely confirms what we are thinking about it being sticky particularly when engine is cold.

[JOMATA Lurker Find all posts View Profile Close JOMATA]

I just looked at it. Mine has the short version. I think I have to add a new one to the current order of a new MAP and filter.

Attached are some screen shots from the scanner.

Regards
Joćo

[JOMATA Lurker Find all posts View Profile Close JOMATA]

Some more.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

From the pics

• Definitely the MAP sensor is reading way too low so hopefully the replacement will sort that issue.
• Were those fuel pressure figures for when it starts OK or cold and hard/slow to start? As the comparison will be what gives you more idea if this is the likely cold start issue.
• The Turbo pic is missing the actual Turbo VN position so not really telling us much but the minimum angle seems high as manual says Normal should be around 7% but not certain if the low MAP reading may be affecting it.

May be interesting for you to graph MAP / Commanded Boost Pressure / Boost Pressure Error / Turbo VN Position (noting that your max out position is around 99%) if you want to see it working to get things to the correct level or not achieving this. Its only for interest as you will need to do the MAP and filter replacement to see if things have improved.

[JOMATA Lurker Find all posts View Profile Close JOMATA]

The fuel pressure pics were from when the engine was starting ok.

Should I take the same pics when it is cold and taking long to start?

As for the turbo, thise are the only readings I get from my scanner. I am really new at this, so maybe I need to dig deeper into the scanner.

Thansk a lot.
Joćo