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Loss of engine power

Posted: Fri Jul 24, 2020 3:39 am
by vi1012
Good day all, I own a 2013 dmax, 2.5l,4jk1 engine.
I am having power loss issues, low power, sluggish acceleration. The turbo was leaking oil, I got that repaired, but same issue. Two mechs scanned the vehicle before and after the turbo repair, and both were not getting a boost pressure reading.
Through out this issue, I discovered the van would run better with the MAF unplugged, but the MAF is reading good. I was told that put the ECM into a default fuel mode thus the performance, but I pulled the hose off the turbo and felt a significant pusk when I rev .. I honestly think I am feeling boost...
One other tidbit, I cannot find the MAP sensor. It is not on top the throttle body as schematics depict. And I have found 4jk1 engine pics without a sensor on that position. So maybe the sensor is elsewhere??

Looking for any ideas!!

Thank you all!!

Re: Loss of engine power

Posted: Fri Jul 24, 2020 8:50 pm
by mydmax
As far as I know the 4jk1 has a boost sensor and it IS in the intake airflow. My digital manual shows it in what looks like a plastic moulded intake section and it has two screws, one either side and awaiting loom plug. If the turbo has been spewing oil the sensor may have been choked with OILY carbon and not indicating correctly to the ECU. As a result the turbo may not be putting out much pressure and little real boost pressure.

Re: Loss of engine power

Posted: Fri Jul 24, 2020 11:13 pm
by vi1012
So this is a pic of an engine I found for sale. This is exactly what my engine looks like. I know the diagram you are talking about, the MAP should be on that black plastic piece on the right, attached to that flat spot, but as you can see, no MAP... and if this is an engine for sale, mine can't be a one off...

Re: Loss of engine power

Posted: Sat Jul 25, 2020 1:33 pm
by mydmax
Yes I see that area and it is where you expected it to be too. I am unsure what they do for boost control sensing. Is there a 3 wire device bolted to the firewall with a hose going to inlet manifold? Petrol engines used that system just wondered it this particular engine does.

DO you know if your engine has a VGT, ie, Variable Vane turbo and is the boost control chamber on the turbo correct and supplied with good hose, no leaks, from the vacuum control system? Mine is 4JJ1 but if the turbo boost control chamber hose has a split or is blocked or the mechanism is not free the turbo won't make much pressure. Alternatively, is the fuel system filters passing sufficient fuel to make power if boost is ok?