High IAC Counts and High MAP
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Joined: May 2001
Posts: 162
From: River Ridge ,LA
High IAC Counts and High MAP
What does it mean if my IAC counts are 60+ at idle (850RPM) and my MAP is 18-19" Hg?
Car has Hotcam. I should be making more vacuum than this.
From what I've read with high MAP reading it usually indicates a vacuum leak, but IAC counts should be low not high.
I have checked for vacuum leaks. Fixed every cracked hose and replaced a bad TB gasket.
Could this be a valve adjustment problem?
I do have random misfires and surge.
Any help would be greatly appreciated...
Data files are in my other post here
Car has Hotcam. I should be making more vacuum than this.
From what I've read with high MAP reading it usually indicates a vacuum leak, but IAC counts should be low not high.
I have checked for vacuum leaks. Fixed every cracked hose and replaced a bad TB gasket.
Could this be a valve adjustment problem?
I do have random misfires and surge.
Any help would be greatly appreciated...
Data files are in my other post here
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Joined: Nov 1999
Posts: 2,801
From: Nashville, TN
You're backwards on your MAP readings. If you were reading kPA, high would mean less vacuum, low would mean more. But if you're looking at inches of mercury, higher = more vacuum. A vac leak would cause your reading to drop.
stock is 21", so with the hotcam I think your MAP reading is fine. Hell I only see 15"
I agree, start by cleaning up your TB, particularly the IAC passages. If they are gunked up it might require more counts to get the proper airflow. As long as the idle is where you want it and you have plenty of vacuum its not really a problem IMO.
stock is 21", so with the hotcam I think your MAP reading is fine. Hell I only see 15"
I agree, start by cleaning up your TB, particularly the IAC passages. If they are gunked up it might require more counts to get the proper airflow. As long as the idle is where you want it and you have plenty of vacuum its not really a problem IMO.
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Joined: Nov 1998
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From: Hell was full so they sent me to NJ
Originally posted by Chris 96 WS6
You're backwards on your MAP readings. If you were reading kPA, high would mean less vacuum, low would mean more. But if you're looking at inches of mercury, higher = more vacuum. A vac leak would cause your reading to drop.
stock is 21", so with the hotcam I think your MAP reading is fine. Hell I only see 15"
I agree, start by cleaning up your TB, particularly the IAC passages. If they are gunked up it might require more counts to get the proper airflow. As long as the idle is where you want it and you have plenty of vacuum its not really a problem IMO.
You're backwards on your MAP readings. If you were reading kPA, high would mean less vacuum, low would mean more. But if you're looking at inches of mercury, higher = more vacuum. A vac leak would cause your reading to drop.
stock is 21", so with the hotcam I think your MAP reading is fine. Hell I only see 15"
I agree, start by cleaning up your TB, particularly the IAC passages. If they are gunked up it might require more counts to get the proper airflow. As long as the idle is where you want it and you have plenty of vacuum its not really a problem IMO.
?Stock cam = 9.5"Hg MAP = 20.5"Hg vacuum
HOT cam = 14"Hg MAP = 16"Hg vacuum (just a guess at what he would see with the HOT cam... .I run 15" MAP at idle with a 230/242 in a 381).
If his MAP is truely reading 18-19"Hg, his vacuum is only 11-12"Hg, and that is too low at idle for a HOT cam.
MAP = BAR - Vacuum, and it doesn't matter whether the scanner is reading in "Hg, or kPa.
Last edited by Injuneer; Jan 6, 2004 at 01:01 PM.
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Joined: Jun 2002
Posts: 537
From: McAllen Tx. USA
If he is seeing 18-20 inches in MAP, that means he is only seeing 10 to 12 inches of vaccum or 30BAR - 20MAP = 10 inches of vaccum.
That is a little to low for a hot cam. My brother's Z sees about 15 to 16 inches of vaccum at around 900 rpm at idle.
Sounds you like have either a significant vaccum leak or valve adjustment is too tight. A random misfire also supports a tight valve adjustment problem, since you may be loading up with fuel with improperly closing/opening valves.
That is a little to low for a hot cam. My brother's Z sees about 15 to 16 inches of vaccum at around 900 rpm at idle.
Sounds you like have either a significant vaccum leak or valve adjustment is too tight. A random misfire also supports a tight valve adjustment problem, since you may be loading up with fuel with improperly closing/opening valves.
Thread Starter
Registered User
Joined: May 2001
Posts: 162
From: River Ridge ,LA
TB and IAC are new. I just put them on the car last night.
IAC counts and MAP have been high since I got the car, which is only around 3 months.
Car has never ran like I think it should.
Changed plugs, wires, O2 sensors, new 52MM TB, new IAC, TPS, and MAP sensors, few new hoses are intake...
I'm going to have the valves checked tomorrow.
Hopefully that is the problem.
So if valves being to tight could cause my low vacuum and misfire, what would cause the high AIC counts or is this related?
IAC counts and MAP have been high since I got the car, which is only around 3 months.
Car has never ran like I think it should.
Changed plugs, wires, O2 sensors, new 52MM TB, new IAC, TPS, and MAP sensors, few new hoses are intake...
I'm going to have the valves checked tomorrow.
Hopefully that is the problem.
So if valves being to tight could cause my low vacuum and misfire, what would cause the high AIC counts or is this related?
Thread Starter
Registered User
Joined: May 2001
Posts: 162
From: River Ridge ,LA
So if valves being to tight could cause my low vacuum and misfire, what would cause the high AIC counts or is this related?
Car is getting valves readjusted tomorrow morning. Is there anything else I should look at while I'm at it?
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