What should be the RPM be for an automatic when the engine is warm and is in Park?
Location: Houston
Posts: 706
My VIN: 16113
Club(s): (SCDC) (DCUK)
What should be the RPM be for an automatic when the engine is warm and is in Park?
Shannon
Location: Vancouver, BC
Posts: 3,385
My VIN: thirty two 'o five
Club(s): (PNDC)
775 +\- 50 I think
Dave
Here, somewhere.
Location: San Francisco Bay Area, Calif.
Posts: 2,084
My VIN: 0934
Club(s): (NCDMC) (DCUK)
Dave is correct. See images below taken from the Manual.
First image shows the spec. Second image shows how to test and troubleshoot.
It doesn't matter what gear the auto transmission is in. Park is fine.
IMG_2617.jpg IMG_2618.jpg
Location: Eglin AFB, FL
Posts: 1,603
My VIN: 3299
Mine is in the 750-800 realm.
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Location: Northern NJ
Posts: 8,582
My VIN: 10757 1st place Concourse 1998
If everything is running as it should then the idle will always be 775 RPM + - 50 RPM's. This spec is for automatics, and 5-speeds, in Park, Neutral, or Drive, A/C on or off. The idle system is supposed to modulate so as to hold the motor at that idle speed when the idle motor system is energized. Typical reasons the idle will not be right include:
Vacuum leaks
Motor needs a tune-up
Leaky/dirty injectors
Bad or misadjusted idle micro
Open brass adjuster screws
Linkage not allowing the throttle lever to return all the way to idle
Misadjusted throttle linkage or a lot of play (looseness) in throttle linkage
Sticking idle motor vane
Mixture not adjusted right
Lambda system not working
Commonly it is not just one cause but a little bit of a lot of things that causes the idle to not be right. Even when set up "right" the idle is not rock steady but will fluctuate or "hunt" around a setpoint which should be within the spec. The better you do the smaller the fluctuation.
David Teitelbaum
Posts: 89
Shannon's car is Megasquirted. I suspect he only asked the stock idle spec to set his EFI IAV similarly.
FWIW: Volvo's B28F idle spec is 900 RPM, even with CIS (Constant Idle Speed -- K-Jet itself is just plain "CI").
Last edited by Bill Robertson's Sock Puppet #1; 12-24-2012 at 03:23 PM.
Location: Houston
Posts: 706
My VIN: 16113
Club(s): (SCDC) (DCUK)
My idle while in Drive is probably 300 RPMs less than when in Drive. According to the discussion here it should be about the same. What could cause the difference? I do have EFI but I wouldn't think that would make a difference.
Shannon
Location: San Francisco Bay Area, Calif.
Posts: 2,084
My VIN: 0934
Club(s): (NCDMC) (DCUK)
Assuming you mean your idle speed drops 300 RPM from Park idle to Drive idle. And jumps back up when going back into Neutral or Park?Originally Posted by lazabby
As noted in the posted manual pages and in other posts the OEM Bosch K-Jet setup compensates for all engine loads and warm-up variables to keep the idle speed within the specified range regardless.
The symptom you report makes sense - IF your EFI system does not have any idle speed modulation/control - OR if that idle speed control loop is malfunctioning. Check your EFI documentation or hardware or get input from an owner running what your are running. Am not familiar with Megasquirt - one of the posts suggests that's what you're running.
I'd guess that a modern EFI system should not run the way you are reporting yours runs. You did not mention what your idle speeds are. Does the car lurch a bit when you engage Drive or Reverse?
Last edited by Rich; 12-24-2012 at 06:53 PM.
Location: Northern NJ
Posts: 8,582
My VIN: 10757 1st place Concourse 1998
Selecting an idle speed is a fairly complicated matter involving exhaust emissions, warm-up time, stalling, etc. You want it as low as you can get it and not have the motor stall or stumble when shifting or accelerating. A little harder to do on a car with a manual transmission since driver technique can have a large effect. I have seen PRV's idle as low as 600 RPM's and still drive well. You really need some automatic idle control, if you run the A/C it can take 200 RPM's off in a hurry. Too low on a manual and it will just stall when trying to move into 1st. On an automatic you can see at least a 200 RPM difference between park and drive. That is too much and if you press down on the gas pedal too fast it will stall. Combine the A/C and holding the car still in Drive and you can see the engine can have a pretty hard time trying to stay running. Now consider driving at night with all of the lights on. At too low an idle speed the alternator cannot make any electric and you are running on the battery. You can experiment with different idle speeds but 775 is a pretty good speed to aim for. That is another peculiarity on Deloreans. On most cars the idle spec is always different on manuals vs automatics (automatics being a little higher).
David Teitelbaum
Posts: 31
My idle speed only drops about 100 rpm when the AC compressor engages, not 200 rpm.
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