Cruising and letting off gas, it causes a wierd rpm drop?

[Nyyankees3511]

I noticed just yesterday when i was cruising at around 40, with the rpms at 2000, with a little acceleration and i let go of the gas the rpms drop and then the needle immediately goes up 1 bar. Say it goes down to 900 and then goes right up to 1000. What could it be?

[Jackass-Jeff]

that's normal... if it's an excessive drop then you may want to clean the throttle body. WHen you let off the accelerator, it tries to drop to idle (lowest RPM w/o running lean at the pace the engine can go at)... so ya... it's normal unless you think it's excessive from what it normally does in your car.

[JAYDEE23]

yeah these cars are a bit odd..sometime cruising about 40-50 and yopu let off the gas it returns to idel other times it doesnt..my throttle body has been cleaned and never goes below800-1000 so i guess this is normal

although i dont like the way the tranny re-engages after the large rpm drop..you cant hit the gas to hard or you will get a slight "knock" (cant think of a good descrptive word for this sound) when the tranny is re-emgaging

[Jetfixer]

I noticed this too, and it seemed to be more pronounced after I cleaned the throttle body. So after much research, I found out that this engine has a fuel cutoff when you close the throttle. Basically the engine is allowed to die until it drops to around 1200 rpm. I'm sure that this is done for fuel mileage and emissions. There's even a test for it in the service manual...

4. INSPECT FUEL CUT OFF PRM
(a) Increase the engine speed to at least 3,500 rpm.
(b) Use a sound scope to check for injector operating noise.
(c) Check that when the throttle lever is released, injector operation
noise stops momentarily and then resumes.
HINT:
Measure with the A/C OFF.
Fuel return rpm: 1,200 rpm

[WTF??]

hahaha this guy, Nyyankees3511, is funny!!!! from starting to shutting off to idle... and now to cruising.... he notices EVERYTHING!!!
not a bad thing to ask, but thats normal as well

[Nyyankees3511]

HAHAHAH WTF ur the man. Yeah im really picky i cant help it.

[NeFaRiOuS_SLE]

Should've just got a Rolls-Royce. It even has anti-lift and anti-dive.

[zoni]

it may just be the transition from open loop to closed loop mode in the ECU... it goes to open loop when you let off of the gas hard (fuel cut-off).

from the factory service manual...