Low Power on a 90ps Transit MK6
Low boost & P0404 & P0149 DTC’s
Hi Richard, you are on the right track, manifold absolute pressure sensor being the right so called PID to query.
Verify your base reading on idle, which should be current atmospheric pressure. It varies between maybe 980 & 1038 millibar, so rounds up to 1 bar. This should peak by 60-70 % under load , or 50% statioanry when revving up. Yours is lower than it should be by a fair amount . As long as base ( idle ) reading is correct, 1 bar ish , then you can take your peak reading as true. This can be due to a sticking turbo wastegate mechanism, intake leak, or faulty / clogged boost ( MAP) sensor. Either there is a leak of ( pressurised) air , or the turbo isnt making high enough pressure to start with. It can also be because the ECU is not requesting the fuel needed to create full power & therefore full boost ,or it’s requesting it from the fuel pump, but the pump or injectors are not able to deliver it, you usually get fault codes with these ECU/fuel pump related issues though & you have only the P0149, so if that code clears & does not return, it’s best to make the tests below.
Wastegate – you can move the actuating rod ( away from the “Pot” with swan neckpliers, the spring is stiff & access tricky but it should move maybe 1/2 inch ( a guess ) & spring back into place
Intake leaks – 1st check rear lower area of intake manifold, you can often find oily deposits, if you put your paw there. They split on the seams, which arent obvious with manifold in place.
MAP sensor – 2.4l engines -2 distinct type – its either mounted on the exit side of the intercooler or on the bulkhead ,the bulkhead mounted one takes its reading from the EGR valve body usually via a spigot & black silicon pipe leading to it . Testing requires a Mityvac or similar to apply pressure directly to the sensor & verify that the applied pressure corresponds with what the diagnostic tool is seeing , in the meantime inspect /clean & make sure spigot is clear , & pipe is in good order, if you have the bulkhead mounted type.
The P0149 in the absense of knocking & super low power is only an issue is its permanant, so clear it & see if it returns after some driving.
P0404 ( EGR) is a failing EGR or one that has a blanking plate & ( on TDDI MK6 Transits) , normally does not cause any issue or power loss unless it’s stuck open , if it was you usually get obvious running & starting issues like smoke or poor starting so in cases of low boost can usually be ignored.
Thanks for the detailed breakdown – really helpful! I’ve been chasing a similar low boost issue on my 90ps MK6 and was starting to go in circles. Especially appreciate the note about Forscan showing absolute pressure – that clears up a lot of confusion around the readings I’ve been getting. Also didn’t realize the wastegate rod could be manually checked like that. Gonna try a few of these tests before diving into replacing parts. Cheers again for sharing your experience – it’s a goldmine for Transit owners like me!