4.8Gl engine jurking on Low RPM's

[Vaatjie]

My patrol is a 2006 4.8GL and here is my problem
1.Trying to keep my RPM between 1100-2000rpm is impossible. You take the rpm slowly up to (for example) 1500rpm and try to keep it there. The engine shuts itself done and goes into idle mode.
2.Driving in the traffic at 60km/h in 3rd or 4th gear the engine will shut down to idle speed, In other words engine brake itself. Now I apply the petrol to accelerate again to maintain 60km/h. This cat and mouse game drives me crazy.
3.Nissan have change the throttle control valve body and spark plugs but the problem is still there. The throttle control valve (butterfly valve in the air intake line) tells the engine that it is in the closed position and therefore shuts the engine to idling speed. This is new and set to 0.46 volts witch is the spec.
Above 2200rpm the problem gone.
Does any body else have the same symptoms or is this normal?

[Wheels]

What error code do you get? Did you see if the camshaft sensor is working. You could also have a CAT (catalic converter ) that is blocking the exhaust flow. I am removing mine some time next week.

[Vaatjie]

Hello wheels
My 2006 patrol was not fitted with a cat, so it can't be that. I'll look into cam sensor.

[tour de frans]

Hallo vaatjie
Jurk jou kar nog,of het jy n andwoord?
Ek mag dalk n andwoord he.
groete Frans

[Gerrit Loubser]

Hi Frans. Please do tell.

[Vaatjie]

Nissan SA has ordered a new computer. This is the most expensive of all the parts that could be change. I have only 3 months off guarentee left and that is why we do it this way. Then they will look at air flow meter and then at cam sensor.
I'll keep you posted.

[JohnBoyZA]

Replacement mechanics at their best!

[Saltman]

Hi Vaatjie

Hou ons asb op hoogte! Ek het darem nog tot die einde van die jaar se warranty oor, maar ek begin die eerste tekens sien op my voertuig ook.
Wanneer die engine op overrun gaan as jy bv teen 'n bult af jou voet van die petrol afhaal dan is dit asof daar 'n solenoid al die petrol toevoer afsny en die enjin slegs teen kompressie hardloop. Trap jy dan weer die petrol, al is dit ook hoe saggies of sensitief dan ruk die enjin. Daar is geen sagte oorgang nie. Klink dit dalk bekend?

[Gerrit Loubser]

Wanneer die engine op overrun gaan as jy bv teen 'n bult af jou voet van die petrol afhaal dan is dit asof daar 'n solenoid al die petrol toevoer afsny en die enjin slegs teen kompressie hardloop. Trap jy dan weer die petrol, al is dit ook hoe saggies of sensitief dan ruk die enjin. Daar is geen sagte oorgang nie.

Saltman, I think that is normal for electronic fuel
injection systems. There is a point where fuel is completely cut off on the overrun.

[tour de frans]

I will keep it short
The throttle control valve body is the throttle boddy.The throttle boddy is controled by your right foot.On the tb(throttle body) is a tps(throttle position sensor)that will tell the ecu what you are doing with the throttle.ie;closed,part or full throttle.When you lift your foot to coast or come to a stop,the ecu will cut the fuel via shutting the injectors for a moment and allow the enjine to idle.The fuel pump always stays on,the fuel pressure regulator regulates the accses fuel back to the tank.(for what its woth;At wot{wide open throttle}there are no vacuum in the enjine,so the fuel pressure regulator lift the fuel pressure +- half bar,to help enrich the fuel mixture.At ct{closed throttle}there is a lot of vacuum that will charge the brake booster and so on,the vacuum on the regulator will less the fuel pressure to help lean the mixture out.There is a air flow meter that messure the air temp and air mass,that will tell the ecu what to do with the injectors and timeing via voltage.)Now when the ecu cut the fuel the car will feel much worse in lower gears than in a high gear.You sould not feel the cut at all.But a big engine will hold a car back much better than a small enjine.Yes you sould not feel the fuel cut.Make sure the sensors talking to the ecu are working and that they are working in sink.I worked on a 4.5 ,the tps was closed but the the butterfly wasnt.the air flow meter is giveing signals to the ecu the ecu see tps closed and the car jurked.Remember dianotic tests only can tell electronic problems and not mechanical.See if the fuel pressure regulator vacuum hose is not broken ie.A ecu dont bom out or give trouble easy,they are very clever.
(sorry vir my engels)
Goete
Frans.