sup guys i have Montero 3,5l sohc petrrol 190k miles recently lots of work done many stuff replaced etc. however i have a problem now m my car starts but it hesitates big time i press pedal all the way and it takes about 2sec before cars drives and on top of that it lacks power Only errors i get are p0170 p0173 which actually manifest with fuel economy before for long time i was getting p0300 but replaced front left o2 sensor and the error is gone

when i look on o2 sensor graphs there are some discrepancies like after the engine warms up it says voltage on all of them is less than 0.1v see first photo before warm up and second after

later it seems they pick up and work fine what i noticed is big difference between what throttle and maf says like with throttle wide open reaction is instant but at the same time maf says it doesn't get enough air until it kicks in (maf was cleand and replaced i tried with two - same effect) when in idle this situation doesn't appear and when in reverse lag is much smaller see next photo - first spike when in drive second idle

on the next photo you'll see spikes drive, reverse, drive, reverse, drive, idle

now because i have access to scrap yard where each week i find some pajero/montero i had checked or replaced following : -injectors - cleaned and checked all spray fine mist resistance pretty same 14,4-14,5ohm -coils tested and replaced tried 3different sets all same results same reads -ignition cables checked fine no cracks burns etc, resistance ok -spark plugs quite new around 3k miles done when i took them out you could see mix was to rich but that was before i replaced manifold and throttle body gaskets for new -map cleaned and replaced -maf cleaned and replaced -fuel pressure regulator replaced -in tank fuel filter replaced -egr valve replaced -vacuum lines checked some replaced -3 out of 4 o2 sensors replaced -new manifold and throttle gaskets

i can't find any vacuum leaks also there were some previously but car did drive fine, there is small exhaust leak on egr tube but will fix that soon fuel pump is odd as it doesn't prime when i turn the key to acc but when i crank the engine it does start and pressure on idle 38psi and on drive 47psi is exactly as in the manual and when i hit the gas pedal i see pressure goes immediately via gauge installed on the feed hose engine runs little rough kind a like it skips to fire also on start engine goes high on revs for tens of seconds than drop about 100-200revs down and holds for tens of seconds than gets back to higher and again drops down so it takes around 4-5min before it settles at about 700-800revs I had run out of ideas i believe those graphs are some clue but I'm not that experienced to tell i hope someone would tell me what could be the reason ? maybe ecu ?

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Scotty Kilmer
Scotty Kilmer

Editor

first, those Mits are garbage at that age. And using junk yard used parts can make analysis worse as you don't know if those used parts are good either. BUT, often ecus go bad on those, have a pro like me diagnose it in person with his equipment hooked up