Strange idle issues with 4.8 (SOLVED)
- Thread starter DarkNinjaSG
- Start date
Good call. BUT, since there was a noticeable difference with the new IAC, I would get a quality one first and double/triple check the install procedures for the new IAC. You can test the TPS and show good and still have intermittent glitches that may not show when testing.
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I cannot stress enough how important getting a Mechanic's Stethoscope is, for helping you find noises and vacuum leaks. I bought this one, after the one I had for years just gave up from use, and this one has the sound cone adaptor that helps pinpoint "parking sensors" problems. Front or rear sensors:
https://www.amazon.com/Lisle-52500-Mechanics-Stethoscope/dp/B0015DLMOO/ref=sr_1_6?crid=RWTFQRHEY1F&dib=eyJ2IjoiMSJ9.LiE-8uCo4JkMcL1kA4_8fO5tM3T6fPp92BxMNF7vj4aw_OH-nR450wthf5eP2a6ok__EgEJwbXQ2jBx2NGDHE0PF0ssDBTB22k29uwmkTrAhumLfrO-kd2_Di0lGXyTP7v3b3vqhi4MSSGzcJzjO8FqNYc7JNcHKcvVw0QrzLiJRQZZHORgYFPDWpgT77ysF35J50knMy6NWr-3pukO-nal2pneV1Rqi4uj56D-3wqSceYbNg_2V_e7oHkDXFZQbKK22ecuZVYyvY3h7eFpH8XorgZt2SeS0ukd0uLrA9nU.vHtlraBNozVawyGqLEakwYYUe2zfpz3wi6hm8Sm3FZU&dib_tag=se&keywords=mechanics+stethoscope&qid=1747589617&sprefix=mechanics+stethoscope,aps,233&sr=8-6&th=1
The cone sensor is great for the parking sensors. When the sensors should be activated, like the rear sensors when in reverse or in the front, they should be making a constant static like sound that you cannot hear without a way to amplify them. You hold the cone up to them and you can easily hear the static sound. If a sensor has no sound, you have found a bad sensor.
You can really zero in on a vacuum leak with these "ears".
https://www.amazon.com/Lisle-52500-Mechanics-Stethoscope/dp/B0015DLMOO/ref=sr_1_6?crid=RWTFQRHEY1F&dib=eyJ2IjoiMSJ9.LiE-8uCo4JkMcL1kA4_8fO5tM3T6fPp92BxMNF7vj4aw_OH-nR450wthf5eP2a6ok__EgEJwbXQ2jBx2NGDHE0PF0ssDBTB22k29uwmkTrAhumLfrO-kd2_Di0lGXyTP7v3b3vqhi4MSSGzcJzjO8FqNYc7JNcHKcvVw0QrzLiJRQZZHORgYFPDWpgT77ysF35J50knMy6NWr-3pukO-nal2pneV1Rqi4uj56D-3wqSceYbNg_2V_e7oHkDXFZQbKK22ecuZVYyvY3h7eFpH8XorgZt2SeS0ukd0uLrA9nU.vHtlraBNozVawyGqLEakwYYUe2zfpz3wi6hm8Sm3FZU&dib_tag=se&keywords=mechanics+stethoscope&qid=1747589617&sprefix=mechanics+stethoscope,aps,233&sr=8-6&th=1
The cone sensor is great for the parking sensors. When the sensors should be activated, like the rear sensors when in reverse or in the front, they should be making a constant static like sound that you cannot hear without a way to amplify them. You hold the cone up to them and you can easily hear the static sound. If a sensor has no sound, you have found a bad sensor.
You can really zero in on a vacuum leak with these "ears".
DarkNinjaSG
Member
I’ll have to look into getting one of those. I put in a Napa Echlin IAC and it seemed to fix all the issues I was having. Now it starts up better and hasn’t had the high idle issue even after driving on the same routes.
99Sierra2500
Well-Known Member
Good to hear you were able to fix it.
