# IAC, go with Delco or aftermarket?



## 70monte (Feb 5, 2008)

The idle speeds both in park and in gear on my 98 K1500 with the 5.7L have been jumping around lately. Sometimes the truck idles like it should and other times it idles high. No SES light. Truck runs great otherwise. I'm thinking about replacing the Idle air control valve to see if this solves this issue. Truck has 118,000 miles on it.

Would you guys stay with an AC-Delco valve or go aftermarket? The Borg Warner valve I can get has a lifetime warranty vs the 1 year on the Delco one. Thanks.

Wayne


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## carkey351 (Oct 18, 2010)

if the aftermarket one is cheaper I'd say go with it. If the AC delco stuff was so good to begin with why is it broke?? That's my idea anyway. Maybe B&B or one of the other GM wizards will jump on here and help you diagnose this problem -they might be able to point to you the solution although the IAC sounds like that could be the culprit..


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## 70monte (Feb 5, 2008)

Well, I did a little more reading and there are a few other reasons the idle could be high. Vacuum leaks are one. I looked around but did not see any broken or cracked lines. I tested the ohms on the valve itself and they were all within spec. I took the valve out to see if it was carboned up but it wasn't very bad. I cleaned it up and reinstalled it. A plugged intake is another reason but mine was clear.

Its possible the gasket under the throttle body is bad somewhere but nothing I could see looks like it is. The idle is not always high so i'm still thinking it might be the valve malfunctioning occasionally. The truck runs too good to have a vacuum leak in my opinion.

As far as aftermarket parts vs OEM, I have always heard that when you are replacing sensors or ignition stuff, stay with factory parts. I know I have had better luck with factory ignition parts compared to aftermarket but I have not had to replace enough engine sensors to get a feel how long they last or work.


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## carkey351 (Oct 18, 2010)

one test that works for me is to spray carb cleaner/brake cleaner around the suspect gaskets; if it start running faster or changes at all when you spray it around a gasket, then that one is probably leaking. leaks can be hard to chase sometimes...as far as the aftermarket vs. factory parts just use what you feel comfortable with, i have had good luck with aftermarket stuff so far, but I guess there is always a first time...


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## BlizzardBeater (Aug 29, 2010)

carkey351;1234478 said:


> if the aftermarket one is cheaper I'd say go with it. If the AC delco stuff was so good to begin with why is it broke?? That's my idea anyway. Maybe B&B or one of the other GM wizards will jump on here and help you diagnose this problem -they might be able to point to you the solution although the IAC sounds like that could be the culprit..


I'm sorry, but any part that is 13 years old and has gone 118,000 miles in my opinion has served its useful life. As far as replacing goes, you know the factory replacement will be plug and play and probably free of issues. Heck if it runs another 118,000 miles it will be worth it right? On the other hand, lifetime warranty is always nice. Go with what you feel best.


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## 70monte (Feb 5, 2008)

I just want a part that will be reliable and work like it should. I do like having a lifetime warrenty vs a year. I can get an AC-Delco sensor online from Rockauto for $90 + shipping. Aftermarket sensors range from $55-$84. I hate to replace this part without knowing for sure if its bad. 

I did discover today that when its idling high in park and I shut the truck off and restart it, the idle is back to normal. I don't know if that points to the IAC being bad or something else.

Last night I checked the resistance of the valve with an multimeter and it was in spec according to my service manual. I also took the valve out and cleaned it with no results. It wasn't very dirty. I checked for vacuum leaks and did not find any. The truck runs too good to have a vaccum leak.

I don't have the correct scanner to check this valve according to the factory service manual. I guess I need to decide what to do.

Wayne


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## 70monte (Feb 5, 2008)

Well, the idle issue seems to have corrected itself. I don't know if the computer needed to adjust itself after I cleaned the valve but now the truck idles like it should. I did end up ordering an AC-Delco IAC valve before this problem corrected itself so I have the part if things go bad again.

Wayne


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## 32vld (Feb 4, 2011)

Vaccum leaks don't come and go.

A gummed up IAC can stick open causing high idle. Cleaning the IAC pintle is like wiping half of your ass and not doing the other side. The IAC passage and the throttle body behind the throttle plate are most likely gummed up. I would of removed the throttle body housing and cleaned the IAC passage, back side of throttle plate and throtle bore as well as the IAC pintle.


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## 70monte (Feb 5, 2008)

I shined a flashlight into the passage and it did not look carboned up. The IAC valve was hardly dirty. I was also going to pull the throttle body but when this was happening, the outside temps were below zero and snowy and I didn't want to spend a lot of time messing with it. About a day after I pulled the valve, the idle went back to where it is supposed to be and has not messed up since. If it does mess up again, I will pull off the throttle body and clean everything. Thanks.

Wayne


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