2008 Ram 1500 5.7 Revs fluctuate when doing 2000 rpm

[kdikert]

I went to a European emission inspection (it's a US car but I have exported it), and they found out that they can not keep a steady 2000 rpm for the emissions test. So while in park, if revving up to 2000 the engine will soon increase to 2500, and then shortly after drop back to 2000. So the rpms fluctuate intermittently while trying to keep the pedal steady. At idle the revs do not fluctuate, at least any that I would notice.

I have not really noticed this, because the increase I revs is somewhat small. So for a layman the truck seems to drive fine, and this can only be observed in park. There have been no warnings or other clear symptoms, I have had the truck for many years, and last year it passed the same emissions test.

There are a few other issues with the truck maybe worth mentioning, but I don't know if they are related. My primary concern is the revs fluctuating, so let's focus on that, but I'll mention these other things as context. 1) I think an exhaust manifold leak is possible, because some of the bolts keeping the manifold heat plate have snapped. However, I'm not picking up any other clear symptoms of an exhaust manifold leak. 2) The engine has trouble warming up to usual temperature, and the temp gauge only rises to 1/4 the way. The gauge acts as if the thermostat is sluggish to open, and then gets stuck open and cools too much. I think the gauge works, because I can feel the heat of the upper radiator hose and cabin heating correlate with what the gauge is reading. I also happened to get some snow stuck in the fan so that it would not rotate, and then it warmed to normal temp, but when I removed the snow the temp quickly cooled down to the lower level. In this incident the radiator went from warm to completely cold when the fan started spinning.

Would anyone have ideas where to start to investigate the revs fluctuating in park, when revving up to 2000?

Ram 1500, year 2008, 5.7 HEMI

 

[kdikert]

Update: I took the truck to the local Ram service. They found out that the gas pedal is very sensitive and difficult to keep in position. There were no other findings or diagnostic codes. They really carefully held the gas pedal in position, and then they got the smog test/inspection to pass. So seems like no problem so far, but I'll see if I can somehow clean the position sensor on the gas pedal.

 

[Mister Luck]

That should have thrown a ( P2104/ P0122 ) soft code, and the technician from the original test should have noted the possibility of the drive by wire sensor, when I read your first post I imagined the intake manifold runners were leaking or if it was tested on a dynamometer the ratio of acceleration was distorted by incorrect tire pressure (Edit) not MDS
I’m curious to how Europe trains their technicians, if it’s the same as CARB standards.
(If I remember correctly cleaning doesn’t work and it can only be replaced )

 

[rzr6-4]

Regarding your temp issue, is the fan always on? I don't remember the exact temp where it kicks on but with the needle 1/4 the way up it should be off.