isuzu 4JX1 very very poor acceleration

[jebo]

hi all,
maybe somebody can share some ideas about this issue?

i have done an injector sleeve (2001 4jx1, A/T) job for a customer that came in as non running/no start car (diesel in the radiator, oil mixed with diesel).
after doing the sleeve, draining of all fluids including fuel return hose, cleaning of fuel tanks, etc...
the car started normally, engine idles smooth, no smokes.
but when i tried to step on accelerator (A/T in park), engine revs up sooooo very slow........(ECT @ 60 deg) will take about 8 to 10 secs to reach 3000rpm.
(ECT @70+ deg.) it gets better, can rev to 3k in a couple of secs.
tried to drive the car and still very poor acceleration.
(ECT @ 90) getting better but still not normal when compared the the other jack in my shop.
all these things happen without a single misfire. it just runs very poor.
runs like it is like pulling a 10 wheeler truck.
engine also starts QUICKLY even in morning starts.

things i have done and checked:
-injector sleeve works
-re-programmed the injector and ORPS (tech2)
-removed and cleaned RPCV
-check intake/exhaust camshaft timing marks
-check cam TDC timing
-oil changed with specified grade
-no MIL
-rail pressure is according to "desired oil rail pressure" (tech2)
-checked MAP 160+/-kpa@2500rpm


things i have "desperately" done:
-swap with other known good ECU
-swap with a known good oil rail w/injectors
-swap with known good APS
-removed the catalytic

things i haven't done but wanted to do. :)
-CHANGE ENGINE! ....LOL


maybe i just overlooked something?
any inputs is greatly appreciated.

thanks much!!!

[Dzltec]

The oil should be a 5w30 or lighter depending on your position.
Basics: was it like this before it stopped? Fit another fuel source to the fuel filter. Make sure the map sensor hole is clean at the inlet manifold, make sure the wastegate and egr are shut. with the koeo what is the rail pressure, it should be .1mpa. These can spin cam gears on the cam, the correct way to check cam timing is to pull the rocker cover off, look at the back of the cams, there are slots, these need to be parrallel with the rocker cover gasket face when at tdc.
Fit a clear line to the return line from the rear of the cylinder head, is there air in it?
Is there any smoke when this happens?

Thats enough to really start thinking after you have done the above.

Andy

[nicamarcos]

The oil should be a 5w30 or lighter depending on your position.

++++1, i think that there jebo have the problem :)

[jebo]

The oil should be a 5w30 or lighter depending on your position. Basics: was it like this before it stopped? Fit another fuel source to the fuel filter. Make sure the map sensor hole is clean at the inlet manifold, make sure the wastegate and egr are shut. with the koeo what is the rail pressure, it should be .1mpa. These can spin cam gears on the cam, the correct way to check cam timing is to pull the rocker cover off, look at the back of the cams, there are slots, these need to be parrallel with the rocker cover gasket face when at tdc.
Fit a clear line to the return line from the rear of the cylinder head, is there air in it?
Is there any smoke when this happens?

Thats enough to really start thinking after you have done the above.

Andy


hi andy,
The car came in as non-running with injector sleeve problem.

yes, oil is 5w30, changed all (3)filters, MAP vacuum passages,
checked and it reads 150kpa+/- @ 2500rpm, egr passage
blocked to insure it stays closed, manifold removed and cleaned,
KOEO pressure -0.0 mpa., very clear exhaust no
smoke whatsoever(seems like running lean), double checked cam timing.
haven't done this "Fit another fuel source", will do it today.
if still no improvements, i will do the x'mission removal.

hmmm i have already worked on several 4jx1's but this one is really unique!:smokin:
been working on and off with this car for over a month now!

as i have said, the only thing i haven't done was swaping the engine with a known good running engine.:idea:

thanks much for the inputs! really appreciate it.
will report back of the results.


edit: attached CSV file of data i collected.

[Poptest]

Try this:

1) Check/adjust pedal position sensor.

2) Check/adjust intake air throttle valve

[jebo]

Try this:
1) Check/adjust pedal position sensor.
2) Check/adjust intake air throttle valve

hi Poptest,
i am confused with the proper setting of the ITP sensor.
manual says hold down by hand the intake valve to fully close position and throttle position should read .27volts (tech2).
please correct me if i'm wrong. i assume then that fully open valve should read more/less 5volts?

but mine reads the way around.
4.something volts @full close and less than 1volt @full open.
should i assume the manual is correct and that maybe somebody had rewired the sensor previously since car was non-running when it came in?

thanks!

[Poptest]

hi Poptest,
i am confused with the proper setting of the ITP sensor.
manual says hold down by hand the intake valve to fully close position and throttle position should read .27volts (tech2).
please correct me if i'm wrong. i assume then that fully open valve should read more/less 5volts?

but mine reads the way around.
4.something volts @full close and less than 1volt @full open.
should i assume the manual is correct and that maybe somebody had rewired the sensor previously since car was non-running when it came in?

thanks!

I don't have a workshop manual at hand but will try to verify.

And since you earlier mentioned that your jack had a fuel to oil mixing problem, I suggest you turn the crank manually to check for possible bearing to crank seizure. This could be a cause for slow acceleration.

[jebo]

hi all,

i just wanted to share the things i did to my issued 4JX1.
this is not a FIX, but just a work around.
i concluded that the engine is really running too lean because exhaust never emits smoke.
what i did was i made a small circuit to adjust the MAP reading.
this circuit adds 20kpa(adjustable) to the original map output so the ECU would think that engine needed more fuel.
now engine seems to run normal, pulls away quickly and a little smoke on WOT.
test drive it for 20km., and all is fine.

thanks to all.