Missing and rough idle

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Dec 21, 2025 | 07:15 PM

JordanJim

Thread Starter

Intermediate

Joined: Sep 2023

Posts: 37

Likes: 14

From: Tennessee

Missing and rough idle

I have been gojng threw everything i can get my hands on. Checked all connections and found no lose or crowded one's. And Its now showing code p0505 and that code is not in the manual. If someone could tell what that code is for i would greatly appreciate it.

Thanks Jim

Dec 21, 2025 | 07:17 PM

CoolBreeze3646

Seasoned HDF Member

Joined: Aug 2006

Posts: 24,423

Likes: 30,643

From: Pennsylvania

Quote:

Originally Posted by JordanJim

I have been gojng threw everything i can get my hands on. Checked all connections and found no lose or crowded one's. And Its now showing code p0505 and that code is not in the manual. If someone could tell what that code is for i would greatly appreciate it.

Thanks Jim

P0505 Idle speed control unstable

https://www.fuelmotousa.com/p-29661-...ble-codes.html

Dec 21, 2025 | 08:29 PM

Max Headflow

Seasoned HDF Member

Joined: Dec 2005

Posts: 19,830

Likes: 7,968

From: poway

If the other codes are gone, I'd check for a manifold leak. Missing O ring on the tmap sensor, manifold seals and any other hoses going to the manifold / throttle body. I'd also check the Throttle Control Actuator connector.

Dec 22, 2025 | 08:39 AM

JordanJim

Thread Starter

Intermediate

Joined: Sep 2023

Posts: 37

Likes: 14

From: Tennessee

Im not sure what I did. But its running fine now. I reset the ECM a couple of time and disconnected the battery and couple of time and let it sit for about 40 minutes each time and the the last time i reset the ECM and started it it ran fine no missing and ithe idle was fine. Like I said not sure what made it straighten out. And want to say thank you to everyone that give me information and things to look at. I really do appreciate it.

Thanks Jim

Last edited by JordanJim; Dec 22, 2025 at 08:41 AM.

Dec 22, 2025 | 01:22 PM

Mr. Mike

Road Captain

Joined: Apr 2010

Posts: 686

Likes: 349

From: Central Utah

Well good for you!
Take it out for an hour and see how it performs. Then do it again tomorrow.

Dec 22, 2025 | 01:46 PM

Max Headflow

Seasoned HDF Member

Joined: Dec 2005

Posts: 19,830

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From: poway

IIRC this is a later TC. Could the issue simply been the On/off/on/off/on thing where the ECU needs to learn where the 0 throttle position is?

Dec 22, 2025 | 09:47 PM

JordanJim

Thread Starter

Intermediate

Joined: Sep 2023

Posts: 37

Likes: 14

From: Tennessee

I took about a 40 minute run tonight and it did fine. No missing and when I came to a stop it idle just fine. And when I get off tomorrow I will take another ride. I did the on/off deal and after I did it I would start it and it was the same and after the third time it started up and went to a normal idle. So I think it just took it a minute to reset or the first couple of time I didnt do the reset right.

Thanks for all.the help Jim