99 350 vortec rough idle

[Raspi454]

I'm not any good at diagnosis, but my 350 vortec doesn't idle nicely, cold or warm. It kinda pulses(?) or it seems like it has a cam in a way, If that makes sense. Going down the road if seems to do alright, but as soon as it idles it's not nice. What do you fellas think? IAC, tune up, something else? I can send a video of it running if that helps.

 

[SUBURBAN5]

I'm not any good at diagnosis, but my 350 vortec doesn't idle nicely, cold or warm. It kinda pulses(?) or it seems like it has a cam in a way, If that makes sense. Going down the road if seems to do alright, but as soon as it idles it's not nice. What do you fellas think? IAC, tune up, something else? I can send a video of it running if that helps.

Kinda sounds like the IAC but then again how many miles on the motor?

 

[Raspi454]

Kinda sounds like the IAC but then again how many miles on the motor?

160k (miles)

 

[SUBURBAN5]

160k (miles)

Last tune up??

 

[Raspi454]

Last tune up??

idk, I pulled this engine out of a yukon we had for plowing, so I don't know, but it probably needs one.

 

[HotWheelsBurban]

I had a similar problem with my 99 5.7 vortec Burb a couple years ago. Replaced the throttle position sensor, then in a week or so, also replaced the idle air control valve. Fixed the wobbly idle with these 2 parts. Both were original ones, truck had like 180 thousand miles on it then. The plungers on these should have some resistance and springiness to them, neither of the old parts did.

 

[mtl111]

+1 on what HotWheelsBurban said. Also, if you're going to replace the those sensors in the throttle body anyway. Remove the throttle body, take the sensors out and clean the throttle body completely, I'm sure its kinda nasty anyway. I know if the back side of the thottle blade gets alot of carbon buildup it can cause a low idle situation. Been there before!

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Raspi454]

+1 on what HotWheelsBurban said. Also, if you're going to replace the those sensors in the throttle body anyway. Remove the throttle body, take the sensors out and clean the throttle body completely, I'm sure its kinda nasty anyway. I know if the back side of the thottle blade gets alot of carbon buildup it can cause a low idle situation. Been there before!

Sent from my SAMSUNG-SM-G930A using Tapatalk

Alright will do

 

[Raspi454]

I had a similar problem with my 99 5.7 vortec Burb a couple years ago. Replaced the throttle position sensor, then in a week or so, also replaced the idle air control valve. Fixed the wobbly idle with these 2 parts. Both were original ones, truck had like 180 thousand miles on it then. The plungers on these should have some resistance and springiness to them, neither of the old parts did.

This is the IAC, should this thing move in and out? Because it doesn't, and you have to push and pull it real hard for movement either direction.

 

[Raspi454]

Probably should include the picture :/

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