iac bad?
04-17-2024, 10:21 PM
#16
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Join Date: Jan 2020
Location: San Francisco
Posts: 57
Re: iac bad?
You shouldn’t need a catch can, because the system shouldn’t be blowing oil into the throttle body. Some people experiencing oil flow used to use a small right-angle filter from Deutsch in place of the plastic elbow in the valve cover.
One “mod” that might increase the oil flow problem is modifying the valve covers for 1.6X full roller rockers. There is a small baffle on the passenger side cover, below the hole/grommet for the PCV vent line. If that baffle is removed, it can increase entrainment of oil droplets when there is backflow in the system.
One “mod” that might increase the oil flow problem is modifying the valve covers for 1.6X full roller rockers. There is a small baffle on the passenger side cover, below the hole/grommet for the PCV vent line. If that baffle is removed, it can increase entrainment of oil droplets when there is backflow in the system.
So I guess that really bad then huh? Probably gotta get that check out then and I'm running stock valve covers
When people have this issue, how do they fix it? Cause I'm pretty sure I'm not the only one lol
04-18-2024, 01:13 PM
#19
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Join Date: Jan 2020
Location: San Francisco
Posts: 57
Re: iac bad?
Like i mentioned above, I replace the hose under the throttle body because it was old & brittle and that made my idle a bit better.
The rpm drop when I slow down slightly die down, but still there.
Also last night when I put the car from drive to reverse, it died and fired back up. I plug the scanner in, and the iac count was at 160. But in park it settle down at 60
04-18-2024, 02:23 PM
#20
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,834
Re: iac bad?
Those readings are too high. Either something is restricting air flow into the engine or in the IAC passages, or the IAC valve is not responding to the PCM's count command. There is no feedback to the PCM with regard to the IAC valves actual position, or whether the valve is even working.
From my experience, and indicated in my 29 page LT1 scanning guide, idle IAC counts should be in the range of roughly 20-40. As engine RPM increases, the counts should increase, typically in the range of 60-100. The value of 160 counts means the PCM has commanded the IAC to its maximum value.
https://www.camaroz28.com/forums/att...canning-r2.pdf
Piston ring blowby increases with piston ring wear and ring gummed up with carbon or sludge. But the LT1 engine, properly maintained, should nor experience that level piston ring wear at 80,000 miles. A possible cause of ring blowby is the engine running excessively rich, allowing raw gasoline to wash down the cylinder walls, removing lubricants.
You mentioned a damaged “hose under the throttle body”. What was that connected to? In 95 the PCV valve vacuum connection to the intake manifold is right below the throttle body. But 94 has the vacuum source is right behind the PCV valve on the side of the intake manifold.
http://shbox.com/1/pcv_pipe.jpg
There is an EVAP line running from the canister in the driver rear fender to the purge solenoid on the passenger side of the intake manifold.
http://shbox.com/1/1995_evap.jpg
From my experience, and indicated in my 29 page LT1 scanning guide, idle IAC counts should be in the range of roughly 20-40. As engine RPM increases, the counts should increase, typically in the range of 60-100. The value of 160 counts means the PCM has commanded the IAC to its maximum value.
https://www.camaroz28.com/forums/att...canning-r2.pdf
Piston ring blowby increases with piston ring wear and ring gummed up with carbon or sludge. But the LT1 engine, properly maintained, should nor experience that level piston ring wear at 80,000 miles. A possible cause of ring blowby is the engine running excessively rich, allowing raw gasoline to wash down the cylinder walls, removing lubricants.
You mentioned a damaged “hose under the throttle body”. What was that connected to? In 95 the PCV valve vacuum connection to the intake manifold is right below the throttle body. But 94 has the vacuum source is right behind the PCV valve on the side of the intake manifold.
http://shbox.com/1/pcv_pipe.jpg
There is an EVAP line running from the canister in the driver rear fender to the purge solenoid on the passenger side of the intake manifold.
http://shbox.com/1/1995_evap.jpg
04-18-2024, 03:00 PM
#21
Registered User
Join Date: Jan 2020
Location: San Francisco
Posts: 57
Re: iac bad?
Those readings are too high. Either something is restricting air flow into the engine or in the IAC passages, or the IAC valve is not responding to the PCM's count command. There is no feedback to the PCM with regard to the IAC valves actual position, or whether the valve is even working.
From my experience, and indicated in my 29 page LT1 scanning guide, idle IAC counts should be in the range of roughly 20-40. As engine RPM increases, the counts should increase, typically in the range of 60-100. The value of 160 counts means the PCM has commanded the IAC to its maximum value.
https://www.camaroz28.com/forums/att...canning-r2.pdf
Piston ring blowby increases with piston ring wear and ring gummed up with carbon or sludge. But the LT1 engine, properly maintained, should nor experience that level piston ring wear at 80,000 miles. A possible cause of ring blowby is the engine running excessively rich, allowing raw gasoline to wash down the cylinder walls, removing lubricants.
You mentioned a damaged “hose under the throttle body”. What was that connected to? In 95 the PCV valve vacuum connection to the intake manifold is right below the throttle body. But 94 has the vacuum source is right behind the PCV valve on the side of the intake manifold.
http://shbox.com/1/pcv_pipe.jpg
There is an EVAP line running from the canister in the driver rear fender to the purge solenoid on the passenger side of the intake manifold.
http://shbox.com/1/1995_evap.jpg
From my experience, and indicated in my 29 page LT1 scanning guide, idle IAC counts should be in the range of roughly 20-40. As engine RPM increases, the counts should increase, typically in the range of 60-100. The value of 160 counts means the PCM has commanded the IAC to its maximum value.
https://www.camaroz28.com/forums/att...canning-r2.pdf
Piston ring blowby increases with piston ring wear and ring gummed up with carbon or sludge. But the LT1 engine, properly maintained, should nor experience that level piston ring wear at 80,000 miles. A possible cause of ring blowby is the engine running excessively rich, allowing raw gasoline to wash down the cylinder walls, removing lubricants.
You mentioned a damaged “hose under the throttle body”. What was that connected to? In 95 the PCV valve vacuum connection to the intake manifold is right below the throttle body. But 94 has the vacuum source is right behind the PCV valve on the side of the intake manifold.
http://shbox.com/1/pcv_pipe.jpg
There is an EVAP line running from the canister in the driver rear fender to the purge solenoid on the passenger side of the intake manifold.
http://shbox.com/1/1995_evap.jpg
And yes that hose that I'm talking about, it connects to the pcv valve on the driver side.
I think my evap is disable in the tune, not sure. Isn't there a canister that is next to the gas tank that connect to the evap sensor on the passenger side? I didn't see one back there when I checked mines.
I don't know about the previous owner, but I have been taking good care of this car so far since I got it. It's not running that lean, cause on the scanner Long terms are usually around 134-140 and short terms cycle around 128-134. I am having spilt blm due to the iac issue.
I Wouldn't be surprise if the previous owner didn't treat it good.
04-18-2024, 07:07 PM
#22
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,834
Re: iac bad?
Throttle blades opening all the way? Opening for the idle air that passes directly through the body into the intake manifold plugged or too small? That can be a problem with the Holley TB, requiring boring a hole in a blade. Some people have the split BLM's supposedly as a result of the restriction.
A restriction in the MAF sensor? I sold someone a CAI, threw a loose CARB-EO certification sticker in it. He didn’t realize it was there, ended up in the MAF. Not likely but had to ask.
Tolerance on the BLM's is +/- 5% versus 128. A 140 is adding 13% extra fuel - too much. Short terms should cycle both sides of 128, and average 128 over time. If the average short term is above 128, that’s when the PCM reduces the long term, trying to get the short term back to a 128 average.
A restriction in the MAF sensor? I sold someone a CAI, threw a loose CARB-EO certification sticker in it. He didn’t realize it was there, ended up in the MAF. Not likely but had to ask.
Tolerance on the BLM's is +/- 5% versus 128. A 140 is adding 13% extra fuel - too much. Short terms should cycle both sides of 128, and average 128 over time. If the average short term is above 128, that’s when the PCM reduces the long term, trying to get the short term back to a 128 average.
07-06-2024, 03:39 AM
#23
Registered User
Join Date: Jan 2020
Location: San Francisco
Posts: 57
Re: iac bad?
Throttle blades opening all the way? Opening for the idle air that passes directly through the body into the intake manifold plugged or too small? That can be a problem with the Holley TB, requiring boring a hole in a blade. Some people have the split BLM's supposedly as a result of the restriction.
A restriction in the MAF sensor? I sold someone a CAI, threw a loose CARB-EO certification sticker in it. He didn’t realize it was there, ended up in the MAF. Not likely but had to ask.
Tolerance on the BLM's is +/- 5% versus 128. A 140 is adding 13% extra fuel - too much. Short terms should cycle both sides of 128, and average 128 over time. If the average short term is above 128, that’s when the PCM reduces the long term, trying to get the short term back to a 128 average.
A restriction in the MAF sensor? I sold someone a CAI, threw a loose CARB-EO certification sticker in it. He didn’t realize it was there, ended up in the MAF. Not likely but had to ask.
Tolerance on the BLM's is +/- 5% versus 128. A 140 is adding 13% extra fuel - too much. Short terms should cycle both sides of 128, and average 128 over time. If the average short term is above 128, that’s when the PCM reduces the long term, trying to get the short term back to a 128 average.
Will a monified lt1 show the same readings as you stated on the BLM? Or will things show differently.
I forget I have a cam sometimes lol. I will assume a cam will probably changed the rhythm of the BLM. Or is my assumption wrong.
(Late Reply I know, been busy lol)
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