seeking help with problem diagnosis.
Drifting
Joined: Mar 2005
Posts: 1,923
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From: GA
Originally Posted by rick lambert
what happens if the IAC is so carboned up-or simply fails so that it can't open? I don't mind being taught, what I do mind is sarcasm in the teaching-which is simply uncalled for! reminds me of the days they used to slap your hands with a ruler if you missed a key in piano class.
Now, if it gets stuck closed the car may not stay running when cold started (yo need a little higher idle on a cold start to stay running) or the car may stall when stopped and the A/C comes on or the fan kicks on because the idle adders tha ECM commands never happen and the engine gets loaded down.
Thread Starter
Pro
Joined: Feb 2005
Posts: 632
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From: Harrisburg, PA 86 Vert w/ 89 wheels
Originally Posted by Morley
A very dirty IAC can cause a "wandering" idle, ie theIAC is commanded to open and give more air for a faster idle but is gummed up and moves slowly. The ECM seeing no real increase from its commands will then command it to open further...the IAC will eventually overshoot the target idle and the ECM will command it closed...same thing happens on the way closed. The idle will have a lazy "wandering" quality rather than a real hunting idle.
Now, if it gets stuck closed the car may not stay running when cold started (yo need a little higher idle on a cold start to stay running) or the car may stall when stopped and the A/C comes on or the fan kicks on because the idle adders tha ECM commands never happen and the engine gets loaded down.
Now, if it gets stuck closed the car may not stay running when cold started (yo need a little higher idle on a cold start to stay running) or the car may stall when stopped and the A/C comes on or the fan kicks on because the idle adders tha ECM commands never happen and the engine gets loaded down.
yay morley! that actually sounds kinda like what I have.
@ rick and cfi - please don't get my thread closed down. I am learning from your debate but it looks like it's turning a little too personal.
@cfi in particular. I appreciate that you're trying to help me. If not the IAC then what direction do you believe would be better to go in?
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Cleaning the IAC is a great place for you to start, it requires very little effort, some carb cleaner and a tooth brush. When you pull it,just clean off as much carbon as you possibly can-hit the inside passages with a little cleaner too. Lube the O ring with some silicon or something similar.Re-install the IAC, it will have to be reset-we can help you with that too. Good Luck
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
As I tried to mention before ....
I had the same symptoms as you were discussing I found that the IAC was stuck , and it would not start cold... and when the A/C was turned on it would try to stall. Having to keep your foot on the throttle until the car suffieciently warmed up... as Morley also mentioned
I hope this gets you going...
Mo
I had the same symptoms as you were discussing I found that the IAC was stuck , and it would not start cold... and when the A/C was turned on it would try to stall. Having to keep your foot on the throttle until the car suffieciently warmed up... as Morley also mentioned
I hope this gets you going...
Mo
Racer
Joined: Apr 2003
Posts: 342
Likes: 0
From: Kalamazoo MI
Just my .02
I had a leaking injector in my LT1 that caused an excessive rich and made popping exhaust like you describe. Idle was poor as well. I did the standard clean throttle blades and IAC passages as well that didn't seem to really help. I also had leaking valve seals that explained my smokiness. I eventually nailed down the leaking injector when I hooked up a scan tool and saw really split BLM's. You need a leakdown test as opposed to compression test to determine if your valve seals are leaking.
There's another recent thread about some cleaner called Seafoam. I have no experience with it but others claim it helped their idle. Your problem is gonna be tough without being able to pull that intermittent code, then again not all problems post codes. But since you're getting a SES light that's the best place to start.
I had a leaking injector in my LT1 that caused an excessive rich and made popping exhaust like you describe. Idle was poor as well. I did the standard clean throttle blades and IAC passages as well that didn't seem to really help. I also had leaking valve seals that explained my smokiness. I eventually nailed down the leaking injector when I hooked up a scan tool and saw really split BLM's. You need a leakdown test as opposed to compression test to determine if your valve seals are leaking.
There's another recent thread about some cleaner called Seafoam. I have no experience with it but others claim it helped their idle. Your problem is gonna be tough without being able to pull that intermittent code, then again not all problems post codes. But since you're getting a SES light that's the best place to start.
Last edited by k99ja04; Apr 17, 2006 at 06:58 AM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by rick lambert
He used a simple analogy-look up the word!
Originally Posted by rick lambert
while you're at it-remember one of my very first posts "the main fan is controlled by the ECM" , twice-not once-but twice you-in your hollier than thou attitude admonished me-said I was wrong!-only to eventually come back and say-"I admitt I didn't check the entire wiring diagram" did I admonish you? NO! learn how to communicate with others and Get a life!
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by illinest
@cfi in particular. I appreciate that you're trying to help me. If not the IAC then what direction do you believe would be better to go in?
RACE ON!!!
Thread Starter
Pro
Joined: Feb 2005
Posts: 632
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From: Harrisburg, PA 86 Vert w/ 89 wheels
to be perfectly fair, I didn't know what a choke is. I have no understanding of carburation so I figure the point is moot. 
So thanks Mo... I wasn't tricked by an improper analogy cause I couldn't key in on improper usage of a car term. No problems.
IAC won't get checked until this weekend at earliest. I'll definately revive the thread when I have more news.
Leaky injector btw.... that's something that I haven't ever thought of. Is that common on these cars? Bad?
So thanks Mo... I wasn't tricked by an improper analogy cause I couldn't key in on improper usage of a car term. No problems.
IAC won't get checked until this weekend at earliest. I'll definately revive the thread when I have more news.
Leaky injector btw.... that's something that I haven't ever thought of. Is that common on these cars? Bad?
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Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Well, it sounds like we're all in agreement that the IAC is the most likely culprit.
illinest, to answer your last question about injectors, whether on vettes or anyother car,they can leak, simply because of age, or infact some new injectors may also leak. Because the majority of discussion here is about vettes we hear alot about leaky injectors-or suspected leaky injectors. It's very easy to check, you simply need a fuel pressure guage. You connect the pressure guage to the schrader valve on the fuel rail,turn the key to the on position and (if the relay is working properly) watch the system pressurize-it should reach somewhere in the 40 range-then you shut the key off and watch the pressure guage-if it drops rapidly, that is a sign pointing to a leaky injector(s). Good luck with the IAC-and let us know.
illinest, to answer your last question about injectors, whether on vettes or anyother car,they can leak, simply because of age, or infact some new injectors may also leak. Because the majority of discussion here is about vettes we hear alot about leaky injectors-or suspected leaky injectors. It's very easy to check, you simply need a fuel pressure guage. You connect the pressure guage to the schrader valve on the fuel rail,turn the key to the on position and (if the relay is working properly) watch the system pressurize-it should reach somewhere in the 40 range-then you shut the key off and watch the pressure guage-if it drops rapidly, that is a sign pointing to a leaky injector(s). Good luck with the IAC-and let us know.