how many rpms at a stop light

[Gregs X]

How many rpms should a 97 4.0 sohc have when in drive with the brakes on, at a stop light. I am seeing 500, seems low, especially with accessories on.
Thanks

 

[koda2000]

my '97 shows about 500 rpm also. seems a little low to me. I'd rather see 650 or so, but who knows how accurate the OE tach actually is.

 

[pbnj22]

my 00 5.0 awd shows about 650-700 and that is pulling it from the computer not the tach.

 

[Blue91Ex]

idle in gear should be lower than idle in park because the engine has more resistance on it from trying to turn the transmision when the brakes are preventing it from doing so, kind of like when you have a power drill with a low battery, it spins fine when its up in the air, but when you put it on a screw that is hard to turn, it bogs down a bit.
doesnt hurt the truck, my 91 does the same thing, idle in park is 800, in drive at a stop is around 500.

 

[1992fordgreen]

500 is orthodox. Heck, mine idles at 900.

 

[2000StreetRod]

desired (commanded) idle speeds

The stock values for my 2000 Sport with SOHC V6 were:
Idle Speed Drive: 624 rpm
Idle Speed Neutral: 656 rpm

If the engine coolant temperature is greater than 206 deg F or less than 142 deg F the engine idle speed will be increased.
If the inlet air temperature is greater than 190 deg F or less than 44 deg F the engine idle speed will be increased.

I agree that 500 rpm is low but like koda2000 posted your tachometer may be inaccurate. Have you removed and then reinstalled the needle for any reason?

 

[koda2000]

The stock values for my 2000 Sport with SOHC V6 were:
Idle Speed Drive: 624 rpm
Idle Speed Neutral: 656 rpm

If the engine coolant temperature is greater than 206 deg F or less than 142 deg F the engine idle speed will be increased.
If the inlet air temperature is greater than 190 deg F or less than 44 deg F the engine idle speed will be increased.

I agree that 500 rpm is low but like koda2000 posted your tachometer may be inaccurate. Have you removed and then reinstalled the needle for any reason?

2000StreetRod, you seem to be the most technically savvy poster on this forum, so I'll ask you... I don't think anyone has ever messed with the tach in my recently acquired '97 SOHC and I think mine is accurate when it reads 500 rpm warm, in gear. there's a screw to adjust the throttle plate on the TB. I know this isn't technically an idle adjustment, but would a slight turn IN of this screw increase the idle speed w/o messing with the TPS or PCM? my concern is that, with such a slow idle, oil pressure would be a bit low. I played with this screw on my '01 SOHC and it seemed to help, but the idle on that truck tended to be erratic, so I wondered if the PCM adapted to it.

 

[2000StreetRod]

throttle stop purpose

I think the main purpose of the throttle stop is to prevent the throttle plate from sticking in the throttle bore. I adjusted mine so the engine just barely idles without dying when the IAC valve connector is disconnected. That way I can detect when the IAC valve goes bad but the engine doesn't die. That usually allows a fully functional IAC valve to have a larger operating range. The valve movement is PCM controlled by pulse width modulation just like the EVR. The duty cycle should be around 50 to 60% during normal operation. That allows for a fairly equal deviation for cold and hot temperatures, change in load (idle/drive), etc. It is no longer necessary to worry about the TPS voltage at idle. The PCM reads the value at ignition turn on and assumes that to be idle. The PCM periodically checks for a lesser value and if detected sets that to the new idle value.

 

[SoNic67]

my '97 shows about 500 rpm also. seems a little low to me. I'd rather see 650 or so, but who knows how accurate the OE tach actually is.

That's why I always switch to "N" at stoplights. Saves gas, less wear on transmission, better oil pressure... It just wears the lever