Idle RPM
 

1992 Dakota- 3.9 Liter V6 LE W/Air Cond

What should the Idle RPMs be ?
Mine is about 400 and sometimes slightly below. No problem idling, no stalling, but hesitation on take off.

These OE tachometers aren't very accurate. Mine idles fine and its registered as low as 200 and high as 800. Off the top of my head a normal idle in park for most vehicles is 800rpm.

Thanks It goes as high as 1000 when cold and first started. I too believe the tach is wrong. It never showed 800 at warmed idle.

I changed spark plugs and the RPMs now seem higher than before. Before idle was about 500, now 700. First gear was 1000-1500, now 1500-2000. When "gunning it" it can reach over 3000 close to 3500. Is there anything to worry about or correct? Thanks

How do you mean first gear is 1500-2000? When you put the truck in first gear (drive), RPMs should not change from idle. When you hit the gas is when the RPMs should increase. And when it shifts out of first gear is entirely dependent on how much gas you give it. If you floor it, yes it won't shift out of gear until high in the rev range. If you accelerate lazily then it'll shift sooner.

Did you disconnect the battery? The PCM has a learn period and idle RPM might be higher for a little while. Either way there is nothing you need to worry about.

Thanks. Yes the battery was disconnected. I meant that the idle rpm in park was higher and in observing the rpms in my normal driving they are higher than before the plug change. For instance I know that driving a particular stretch of road the rpms were always 1500, now are 2000; I realize the amount of accelerator applied will affect the rpms, it's just that they seem higher now. I'll see what happens after a few weeks but thanks for the "no need to worry."

1993 Dodge Dakota LE, 5.2L

I oft wondered about idle RPM too. I recently changed out my crankshaft and camshaft sensors and it seemed my idle dropped from about 700 to 400. But then after checking it several more times I cannot tell what the idle is. I see it at 400, 500, 600, 700, 800 after it's warmed up. All over the place. Seems like it prefers 500ish for the most part but it does fluctuate. But the dang thing purrs like a kitten so I leave well enough alone.

I will say that if you're using the indash tach, that sucker may be way WAY out of calibration.

Try with an external tach and see what happens.

RwP

I think you're right Ralph. The onboard tach can be a bit emotional. Better than nothing but not to be trusted for accuracy. Just hearing/feeling the idle relays as much or more info than the dash tach.