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I just dropped a re-built 2.0L engine in a 07 Sentra(someone forgot about checking oil). It has been one headache after another and this present one has me scratching my head in confusion. I have done the throttle re-learn and it will idle fine for about 30 seconds then it will stumble almost die for 3-4 seconds then catch itself and repeat. The timing of it all is constant, you can set your watch to when it will stumble. Idles at 7-750(30seconds) drops to 500(3-4seconds) then jumps to 1100(2seconds) then back to 7-750. The HO2’s read front 25% the rear reads 9.2% and no fluctuation in rear one at all. Changed rear and it dropped to 7.4% but still no adjustment to compensate for the 25% front. Scanner says lean so have chased down no vacuum leaks to be found. Car drives great off idle but stumbles at idle. Anyone run into this problem before? If so could use some advice.
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[quote=”r8er4ever” post=129395]eventually it will set a P0300 after enough stumbles.[/quote]
Either the random misfire is causing the idle issue or the idle issue is causing the misfire.
Are the plugs new? NGKyes on the plugs. And i think the idle is cause of 0300 because no misfire off idle. The fact that the rear o2 is not trying to compensate for the fronts 25% is strange and don’t know for sure but I doubt 9.4% is max for the rear to be able to adjust.
[quote=”r8er4ever” post=129402]yes on the plugs. And i think the idle is cause of 0300 because no misfire off idle. The fact that the rear o2 is not trying to compensate for the fronts 25% is strange and don’t know for sure but I doubt 9.4% is max for the rear to be able to adjust.[/quote]
The rear o2 does not adjust fuel trim. The front one does. Try this test.
unplug the MAF and start the car. don’t give it any gas. see if the car
idles better. with a scanner see what ltft does should be -25% with MAF
unplugged.Well after much effort(including removal of intake 3 times) got it solved.Turns out the bottom injector o-rings that came in the gasket set from the engine re-builders, were not thick enough to create a good seal. Seal was strong enough to prevent detection by my smoke machine(1-7P.S.I.) but under full intake vacuum would allow leakage and then under boost would allow a seal. And of course only on cyl 2 and 3(which are hidden under the intake plenum). Changed all 4 with dealer o-rings and car idles like new :woohoo: :woohoo: :woohoo:
THANKS ALL :cheer:
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