This vehicle has erratic idle speed?

SUB 4-40

MEMBER
2002 DODGE DAKOTA
4.7L
V8
4WD
AUTOMATIC
193,000 MILES

In park, RPMs run from 750 to as high as 1,400. Varies back and forth within that range every 20-30 seconds. Seems a little more intense with the A/C off. Any advice?

Thursday, October 26th, 2023 AT 11:10 AM

4 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

I have seen a bad TPS sensor, or a vacuum leak that can cause this problem, do you have a check engine light on? We should run the codes; this guide can help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If no codes are present, then I would clean the throttle bore and IAC motor (#4) here is the location and a guide to help as well:

Check out the images (below). Please let us know what happens.

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Thursday, October 26th, 2023 AT 4:53 PM

SUB 4-40

MEMBER
2 POSTS
2002 DODGE DAKOTA
4.7L
V8
4WD
AUTOMATIC
193,000 MILES

Erratic idle. In reply about the Dodge Dakota, it has had three new IAC Values in the last 20 months. They work for a while then it returns to the erratic idle. There is no check engine light on, nor has there been one come on anytime while this erratic idle is going on. Knowing these two points, do you have any more ideas on what I should check out?

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Thursday, October 26th, 2023 AT 6:38 PM (Merged)

SUB 4-40

MEMBER
2 POSTS

In reply about the Dodge Dakota, it has had three new IAC Values in the last 20 months. They work for a while then it returns to the erratic idle. There is no check engine light on, nor has there been one come on anytime while this erratic idle is going on. Knowing these two points, do you have any more ideas on what I should check out?

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Thursday, October 26th, 2023 AT 6:38 PM (Merged)

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

An erratic idle can be caused by a few different things. For example, the IAC (which you have replaced), an engine vacuum leak, fuel pressure, or the need for a tune-up. I'm sure there are other causes, but I would think these are the most common.

When you installed the new IAC, did you confirm the air passage was clear and carbon-free? If not, check that.

Here is a link that explains how to service the IAC:

https://www.2carpros.com/articles/idle-air-control-valve-service

If that doesn't help, I would be checking for engine vacuum leaks.

Here is a link that explains how to check:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Try these and let us know the results.

Take care,

Joe

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Tuesday, May 7th, 2024 AT 7:04 PM