Nissan Navara D40 2007 Auto having poor fuel economy and low in power after engine rebuild

[Ziad]

Hi Gurus,

Some guidelines are requested from your experience, I recently got my Nav engine rebuild which also included replacing the Turbo with a new one, new BCS (boost control solenoid), servicing of SCV (suction control valve), MAF (mass air flow) sensor, additionally all vacuum hoses are checked to be OK, Turbo actuator does gets lifted once engine starts (though does not oscillate like in the old Turbo did !), New Air filter and a new Nissan genuine fuel/diesel filter installed.

It starts well in the morning but once you accelerate from idle, it does not accelerates well as was earlier (before engine rebuild) rather damps down and if you release the push on the accelerator a bit, it gets better but still you don't feel the turbo boost as was before.

It's fuel consumption has dropped to approx 7/8 km/litre from around 10/11 earlier with no or very less kick in the boost.

I have OBD adaptor and Torque (pro) app which does show boost up to 15/16 PSI at about 3500 RPM but you still don't feel the pull while accelerating hard rather sluggish with high vibrations..

One important observation which is different now from the pre engine rebuild status is the "Calculated Engine Load in %" in the "Torque" app which earlier doesn't or very seldom crossed 50/60% even running on 120 km/hr speeds which is now hiking to 95/100% even if the vehicle is accelerated from the Idle position or even revving while standing idle.. apparently air/fuel mixture is not right or its running in a "retarded" timings..

No or very less smoke is observed even with hard throttling..

Please your guidance is requested.

Thanks

Ziad

 

[tweak'e]

i would check the injectors are set into the ecu correctly (ie they reinstalled them on different cylinders).
also check compression.
check no blockages in the intake, no loose pipes, blocked up air filter etc.
also try it with engine breather disconnected (and air intake side sealed off). not uncommon to get large amounts of blowby on reco engine until rings bed in.

i would have to check the book but an old engine reco trick is to fit the biggest head gasket, which gives it lower compression and makes it run like crap.

 

[tweak'e]

to add, i only have the book for early D40 and it lists 6 sizes for head gaskets. the size indicator is external on the oil filter side of the engine, a number of notches which may be in two places on the tab (count them together).

 

[Ziad]

Great inputs... just to update, injectors were mapped back in the ECU post recon, intercooler was serviced then new clamps were installed so not much on the leak side, fuel rail is generating around 4-5k psi at idle and 21-23k psi in running condition..
any way on checking the compression?

 

[tweak'e]

any way on checking the compression?

get a diesel mech to run a compression test.
you could do it yourself but last time i looked diesel compression testers are a bit expensive.

 

[Ziad]

Ok thanks for the help..

 

[Ziad]

Guys,

One question, is there a way to tighten Head bolts without removing the camshaft, or with removing only camshaft's holding brackets? I fear that could be due to head bolts not properly torqued as per recommendations when the engine was rebuild..

Thanks

Ziad

 

[[email protected]]

you would have a compression leak and blow the water out of radiator, and also oil leaks and coolant leak around the outside of head gasket. as mentioned before ,measure the compression.. any one tried a cheap compression tester does come with metric fittings

 

[tweak'e]

Guys,

One question, is there a way to tighten Head bolts without removing the camshaft, or with removing only camshaft's holding brackets? I fear that could be due to head bolts not properly torqued as per recommendations when the engine was rebuild..

Thanks

Ziad

not sure.
but you can't just tighten the head bolts. it would mean replacing the bolts.
also i highly doubt that even if head bolts are loose it will make no difference to power output. loose bolts will make head gasket leak.

 

[Ziad]

Hi tweak'e,

Thanks for your opinion/reply, actually in an another forum, with the same query, i had received a reply which stated that same symptoms and poor fuel economy was observed when he had the head replaced which later on burnt the head gas kit and the cause he stated was loose head bolts.. so i got skeptical since I also had the engine rebuild where this lag of acceleration and poor fuel economy qas not there prior to it.. so looked into having an opinion..

Thanks

Ziad

 

[[email protected]]

i have checked head bolts before , with some reccomendations where you say torque to 30lb then finish off with a dial app where you then tighten to 3/4 of a turn its possible if one is careless to have some bolts with less torque than others. First time i did this i had to work out where the torque setting should have been by picking on one bolt which i had marked as being the one which i carefully got the dial spot on,went back to it ,used torque wrench and gradually adjusting untill tool clicked ,i then set it back 5 ft ib checked all the bolts and did find a couple undertorqued. I then did the round again with + 5 lb. you must do the circular pattern. so find the torque of one bolt set wrench back 5 ft ib do rounds then up 5 lbs do the round again. I did come across what you suspect on a tractor which had been recode , if i rember there was coolant leak first time it was used and driven back to shed,without overheating. it actually also had an air leak in fuel system, as usual one thinks its fixed with first issue but there is also a secondary problem

 

[Kzin]

I have OBD adaptor and Torque (pro) app which does show boost up to 15/16 PSI at about 3500 RPM but you still don't feel the pull while accelerating hard rather sluggish with high vibrations..

that seems a bit low

Try doing the pedal dance, to do a fuel system reset. Any changed Fuel related components require it, so Turbo, SCV, MAF, Boost control valve etc.

 

[Ziad]

i have checked head bolts before , with some reccomendations where you say torque to 30lb then finish off with a dial app where you then tighten to 3/4 of a turn its possible if one is careless to have some bolts with less torque than others. First time i did this i had to work out where the torque setting should have been by picking on one bolt which i had marked as being the one which i carefully got the dial spot on,went back to it ,used torque wrench and gradually adjusting untill tool clicked ,i then set it back 5 ft ib checked all the bolts and did find a couple undertorqued. I then did the round again with + 5 lb. you must do the circular pattern. so find the torque of one bolt set wrench back 5 ft ib do rounds then up 5 lbs do the round again. I did come across what you suspect on a tractor which had been recode , if i rember there was coolant leak first time it was used and driven back to shed,without overheating. it actually also had an air leak in fuel system, as usual one thinks its fixed with first issue but there is also a secondary problem

Hi Izzibri,

Great inputs, so it's possible.. will check the bolts and the procedure.. but one thing, in D40, camshaft runs over some headbolts, how'd you managed it?

Thanks

Ziad

 

[Ziad]

Try doing the pedal dance, to do a fuel system reset. Any changed Fuel related components require it, so Turbo, SCV, MAF, Boost control valve etc.

Hi Kzin,

Did lots of efforts but couldn't trigger the ECU reset via the pedal dance procedure.. though does it by battery terminals disconnect way.. no difference..! Did the SCV service, new fuel filter also, new BCS, new Turbo, MAF cleaned as well...

Thanks

Ziad

 

[[email protected]]

Ziad i havnt worked on the d40 head dont know if you can fit (how to use crow foot tork wrench ) youtube.. or because of the torque required a ring spanner one (plug in tools for torque wrench) the issue with these is that it can change the distance between centre of bolt to grip position .you need a FORMULAR to work out where to place your grip ,the special designed handles have groves in them so you change you grip position.

They are too expensive to buy and a good way to snap a bolt if you make a mistake

 

[Ziad]

Ziad i havnt worked on the d40 head dont know if you can fit (how to use crow foot tork wrench ) youtube.. or because of the torque required a ring spanner one (plug in tools for torque wrench) the issue with these is that it can change the distance between centre of bolt to grip position .you need a FORMULAR to work out where to place your grip ,the special designed handles have groves in them so you change you grip position.

They are too expensive to buy and a good way to snap a bolt if you make a mistake

Ok thanks mate..

Ziad