I have noticed since the day we bought our 94', the RPM drops from about 750 +/- 50rpm in Park to about 550 +/- 50rpm in drive. I noticed from my mothers car, a saturn, but a car all the same that the rpm when fully warm doesnt drop when switching from park to drive.
My question is is this normal to drop the rpm that much? Could it possibly be a vacuum leak, or air intake leak?
The car drives great, but at idle it seems to drop considerably. There is no rough idle, but vibration possibly due to motor mounts, but mostly third mount (transmission). MAF sensor is fine, done tests and doesn't affect idle in any way.
Idle RPM drop - Park to drive
-
SanCarlosQ45
- Posts: 260
- Joined: Sun Feb 10, 2008 1:47 pm
- Car: 1994 Q45 144,000
2013 Nissan Xterra Pro-4x
1967 MGB GT Special - Location: Ooltewah, TN
-
maxnix
- Posts: 22627
- Joined: Mon Jul 22, 2002 8:11 pm
- Car: 1995 Infiniti Q45
1995 Infiniti Q45t
2000 Infiniti Q45
Re: Idle RPM drop - Park to drive (SanCarlosQ45)
Any maintenance history? Especially on intake path and fuel system?
How's your IAC valve?
750 rpm by professional instrumented tachometer or dashboard? Should be about 650 rpm.
How's your IAC valve?
750 rpm by professional instrumented tachometer or dashboard? Should be about 650 rpm.
-
SanCarlosQ45
- Posts: 260
- Joined: Sun Feb 10, 2008 1:47 pm
- Car: 1994 Q45 144,000
2013 Nissan Xterra Pro-4x
1967 MGB GT Special - Location: Ooltewah, TN
Re: Idle RPM drop - Park to drive (maxnix)
We did the fuel pump about two months ago with the o-ring. Put a can of BG44k in the gas about a month ago, didn't seem to do very much other than increase the smoothness of acceleration. I have ohmed the injectors and they are about 13-14 I believe.
We replaced the PCV valve, could have cleaned it, but replaced it anyway. It wasn't too dirty. The throttle body was spotless which surprised us. I cleaned the EGR valve, which doesn't pertain to the idle speed.
The real question is about the IAC valve which I have cleaned thoroughly twice. It seems when I am driving about 45-55 mph when I let off on the accelerator the car hesitates, which from what I have read the IAC valve controls in some way the deceleration of the motor when letting off on the throttle. I believe that this started right after I removed the valve the last time, possibly the EGR valve.
This is all off of the in car tach, that is why I said +/- 50rpm to compensate for the inaccuracy. This may not be an accurate compensation but you get the idea.
We replaced the PCV valve, could have cleaned it, but replaced it anyway. It wasn't too dirty. The throttle body was spotless which surprised us. I cleaned the EGR valve, which doesn't pertain to the idle speed.
The real question is about the IAC valve which I have cleaned thoroughly twice. It seems when I am driving about 45-55 mph when I let off on the accelerator the car hesitates, which from what I have read the IAC valve controls in some way the deceleration of the motor when letting off on the throttle. I believe that this started right after I removed the valve the last time, possibly the EGR valve.
This is all off of the in car tach, that is why I said +/- 50rpm to compensate for the inaccuracy. This may not be an accurate compensation but you get the idea.