# Intermittent high idle **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** dakota, dodge\ **Created:** [October 1, 2012, 4:39pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760 "2012-10-01T16:39:14Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![greenmonster](https://avatars.discourse-cdn.com/v4/letter/g/7bcc69/32.png) [@greenmonster](https://community.cartalk.com/u/greenmonster)\ **Post date:** [October 1, 2012, 4:39pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/1 "2012-10-01T16:39:14Z")
vehicle 1997 dakota engine 3.9L w/auto trans. The vehicle exhibits an intermittent high idle. I have replaced the usual IAC stepper motor and checked the tps for proper function, also completely cleaned, inspected and relubed the throttle body and linkage. According to my Inova 3140, there are no codes and the temperature sensors and tps percentage are reading correctly. Also the battery and charging system are functioning correctly. I do not have bi directional capability or the ability to monitor any of the pid’s One other thing is that she also has a slight rough idle, but that could be the 200,000 miles. Thank You ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [October 1, 2012, 11:07pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/2 "2012-10-01T23:07:18Z")
These are the typical symptoms for a vacuum leak. The rough idle indicates that it is the intake manifold gasket, most other vacuum leaks affect all cylinders equally so the idle is less likely to be rough. Try spraying something like propane, either, carb cleaner, throttle body cleaner or even WD-40 all around the intake manifold gasket, when you come to the leak, something will change depending on what you are spraying. I prefer to use WD-40 myself. ---
**Author:** ![greenmonster](https://avatars.discourse-cdn.com/v4/letter/g/7bcc69/32.png) [@greenmonster](https://community.cartalk.com/u/greenmonster)\ **Post date:** [October 3, 2012, 5:16pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/3 "2012-10-03T17:16:27Z")
I did mention this is Intermittent, Unlees the vacuum leak is on the downstream side of a vsv I don’t see is how this would be the cause. What I failed to mention is that the idle is only high at start up and if I turn the key to the off position then restart the engine the idle is normal. Thank You ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [October 3, 2012, 9:28pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/4 "2012-10-03T21:28:29Z")
If it’s only doing it at start up, than I’d suspect fuel line pressure loss (the line is losing pressure and it’s taking a moment for system to repressuriize and the fuel pressure regulator to stabilize). ---
**Author:** ![greenmonster](https://avatars.discourse-cdn.com/v4/letter/g/7bcc69/32.png) [@greenmonster](https://community.cartalk.com/u/greenmonster)\ **Post date:** [October 4, 2012, 1:22am UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/5 "2012-10-04T01:22:47Z")
No that is not the case/ loss of fuel pressure would cause a hard start or no start condition. But thank you for the ideas. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [October 4, 2012, 2:49am UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/6 "2012-10-04T02:49:59Z")
Normally that’s true, but a pressure pulse on startup could mislead. You seemed reluctant for some reason to accept the possibility of a vacuum leak, which could be anywhere past the MAF sensor…or even a leak just upstream of the upstream Ox sensor (an exhaust leak would affect the metering if it were in a spot that causes the Ox sensor to register a higher oxygen level than there actually is, and that would cause the ECU to enlarge the injector pulsewidth). So I thought I’d add a WAG thought. The reason I didn;t mention the exhaust leak previously is that I’d normall expect an exhaust leak of that type to cause a wandering idle rather than one that settes down. ---
**Author:** ![greenmonster](https://avatars.discourse-cdn.com/v4/letter/g/7bcc69/32.png) [@greenmonster](https://community.cartalk.com/u/greenmonster)\ **Post date:** [October 4, 2012, 6:41pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/7 "2012-10-04T18:41:11Z")
No maf on this antique. the pressure pulse theory is easy enough to check. Regarding the o2 sensor and an oxegon rich enviroment I would agree if it were all the time same with the vacuum leak theory but not intermittent and as I explained earlier if the key is cycled it starts at normall rpm. I am starting to believe that the only way to catch the culprit is to record the labscope readings from the input and output signals upon start up. Thank You again for the input ---
**Author:** ![Wandress](https://avatars.discourse-cdn.com/v4/letter/w/b9e5f3/32.png) [@Wandress](https://community.cartalk.com/u/Wandress)\ **Post date:** [November 22, 2017, 4:49pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/8 "2017-11-22T16:49:53Z")
Did you figure this out?? I’m having the same problem. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [November 23, 2017, 6:34pm UTC](https://community.cartalk.com/t/intermittent-high-idle/74760/9 "2017-11-23T18:34:31Z")
Click on OP’s avatar, and you’ll have the option of sending him a personal message If you don’t do that, the chances of him even knowing you asked a question are remote, as he hasn’t been active on this website since November 26th, 2012