Typical IAC counts at startup?
Thread Starter
Instructor
Joined: Nov 2002
Posts: 107
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From: clarendon hills il
Typical IAC counts at startup?
What should the IAC counts be at startup? I have a '91 stock vette.
My IAC counts is at 160 before startup and changes to around 90 immediately after starting. Over the course of a couple of minutes it gradually drops to around 50. Is this normal?
My problem that I am trying to diagnose is that once the car is started, I get "smoke" out of the exhaust, and it smells like a "lean" mixture (rotten egg smell). Once the car goes into closed loop, the smell goes away and the smoke is gone as well.
Thanks,
Howdo
My IAC counts is at 160 before startup and changes to around 90 immediately after starting. Over the course of a couple of minutes it gradually drops to around 50. Is this normal?
My problem that I am trying to diagnose is that once the car is started, I get "smoke" out of the exhaust, and it smells like a "lean" mixture (rotten egg smell). Once the car goes into closed loop, the smell goes away and the smoke is gone as well.
Thanks,
Howdo
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
I'm not sure about the IAC counts thing but it......sounds to me like you got leaky valve seals (rubber umbrella seals) The oil and leak past the seals and drip oil into the cylinders which creates smoke for the first few seconds of run time after start up.
What color is the smoke?
What color is the smoke?
Safety Car
Joined: Sep 2003
Posts: 3,599
Likes: 24
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
Those IAC steps are fine. 160 is the programmed start up position, then it will adjust down to hit the target idle rpm. I don't think IAC position has anything to do with the issue.
Any other codes? What do the BLMs look like? What do the spark plugs look like?
Any other codes? What do the BLMs look like? What do the spark plugs look like?
Thread Starter
Instructor
Joined: Nov 2002
Posts: 107
Likes: 0
From: clarendon hills il
The exhaust really smells and the car runs poor at startup, so I didn't think it was leaking oil. For a long time now, I have had the smell at startup. Just recently, the car wouldn't stay running (until closed loop) unless I kept my foot on the gas. Now the car will stay running but I still get the smell and the smoke.
The BLM are at about 135. Typically the BLM is around 141 for my car since I have the pink topped injectors which I understand have a lower flow rate than stock.
I can check the plugs next. What should I be looking for?
Thanks,
Howdo
The BLM are at about 135. Typically the BLM is around 141 for my car since I have the pink topped injectors which I understand have a lower flow rate than stock.
I can check the plugs next. What should I be looking for?
Thanks,
Howdo
Team Owner
Joined: Feb 2006
Posts: 23,146
Likes: 117
From: San Antonio Texas
I'm going to sound like Borat here...WHAAAT??? I just gotta ask... How are you guys finding out these counts? Are you using a computer or something? I'd really like to know how to diagnose problems with that much detail. I grew up with screwdrivers and wrenches but the computer age is grinding me down. I really need to learn how to do these things now.
Thread Starter
Instructor
Joined: Nov 2002
Posts: 107
Likes: 0
From: clarendon hills il
If I can do it, anyone can...
I'm going to sound like Borat here...WHAAAT??? I just gotta ask... How are you guys finding out these counts? Are you using a computer or something? I'd really like to know how to diagnose problems with that much detail. I grew up with screwdrivers and wrenches but the computer age is grinding me down. I really need to learn how to do these things now.
First, I got some good books explaining the subject. My favorite is Corvette fuel injection by Probst. Reading posts on the forum will help too.
Second, I built a modem based on the plans on Craig Motes website. You can buy a pre-made cable/modem from the same site.
Third. Get a scanner program. I use TunerPro RT (free) which allows you to monitor live all the sensor data from your car (and much more).
The trick is understanding the values and knowing what they mean.
good luck
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
To the poster 160 counts is normal on cold start-up, and counts from there are based on coolant temps and will go down accordingly till operating temps occour. w/out more info the smells you mention sound like a cat/emmision issue.
Safety Car
Joined: Sep 2003
Posts: 3,599
Likes: 24
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
The exhaust really smells and the car runs poor at startup, so I didn't think it was leaking oil. For a long time now, I have had the smell at startup. Just recently, the car wouldn't stay running (until closed loop) unless I kept my foot on the gas. Now the car will stay running but I still get the smell and the smoke.
The BLM are at about 135. Typically the BLM is around 141 for my car since I have the pink topped injectors which I understand have a lower flow rate than stock.
I can check the plugs next. What should I be looking for?
Thanks,
Howdo
The BLM are at about 135. Typically the BLM is around 141 for my car since I have the pink topped injectors which I understand have a lower flow rate than stock.
I can check the plugs next. What should I be looking for?
Thanks,
Howdo
w/ msevenThe high BLMs indicate a lean condition, so additional fuel is being added to compensate. If you replaced your stock injectors with those having a lower flow rate, then I would expect BLMs to be high. I'm sure the O2 volts are very low during open loop as well. Why were the injectors replaced in the first place? Did this issue surface only after the injectors were replaced?
Checking the plugs would serve to further confirm the lean condition at start up.
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Thread Starter
Instructor
Joined: Nov 2002
Posts: 107
Likes: 0
From: clarendon hills il
w/ msevenThe high BLMs indicate a lean condition, so additional fuel is being added to compensate. If you replaced your stock injectors with those having a lower flow rate, then I would expect BLMs to be high. I'm sure the O2 volts are very low during open loop as well. Why were the injectors replaced in the first place? Did this issue surface only after the injectors were replaced?
Checking the plugs would serve to further confirm the lean condition at start up.
I guess I figured that since my integrator is at 128, that it didn't matter that block learn was at 141. I didn't consider that startup could be afftected too. I wonder if its time to invest in a Holly AFPR.
What would the plug look like for a lean mixture?
Howdo
Safety Car
Joined: Sep 2003
Posts: 3,599
Likes: 24
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
Bone white porcelain can indicate a lean idle, but it can also become bone white at WOT from the excessive heat generated.
The smoke and smell at start up could mean that it's running rich. The high BLMs show that the ECM is adding fuel, but it may be due to a false reading (or real problem) elsewhere. A lazy or malfunctioning O2 can cause these issues. Check the plugs
The smoke and smell at start up could mean that it's running rich. The high BLMs show that the ECM is adding fuel, but it may be due to a false reading (or real problem) elsewhere. A lazy or malfunctioning O2 can cause these issues. Check the plugs
Pro
Joined: Jun 2007
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From: the best car on earth ,vettes are best
hi guys,
sorry to but in on your thread .
i was wandering what should the (blm) block learn numbers be roughly on a l98 engine when just starting up and when warm/idleing please?
and what is the ldeal air/fuel ratio should be please ?
i now know that iac should be 160 when start up then reduces back dwon lower e.c.t.
cheers
shae
sorry to but in on your thread .
i was wandering what should the (blm) block learn numbers be roughly on a l98 engine when just starting up and when warm/idleing please?
and what is the ldeal air/fuel ratio should be please ?
i now know that iac should be 160 when start up then reduces back dwon lower e.c.t.
cheers
shae
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
hi guys,
sorry to but in on your thread .
i was wandering what should the (blm) block learn numbers be roughly on a l98 engine when just starting up and when warm/idleing please?
and what is the ldeal air/fuel ratio should be please ?
i now know that iac should be 160 when start up then reduces back dwon lower e.c.t.
cheers
shae
sorry to but in on your thread .
i was wandering what should the (blm) block learn numbers be roughly on a l98 engine when just starting up and when warm/idleing please?
and what is the ldeal air/fuel ratio should be please ?
i now know that iac should be 160 when start up then reduces back dwon lower e.c.t.
cheers
shae
Last edited by mseven; Sep 13, 2007 at 08:14 AM.
