1992 5.0L mustang MS2 PnP, heads, cam, intake. Idle with AC on?

AUBURN1111

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Oct 17, 2000
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#1
Im trying to get this thing to idle with the increased load of the air-conditioning compressor on. Ive tried idle targets of 800, 850 and 900, when AC is turned on rpm drops then surges then shuts the motor off. If you hold the throttle at 1500rpm turn AC on then let off same result, doesnt seem to catch the idle rpm with the increased load. @a91what Any "Air-conditioning Idle up" settings that may help resolve this?
 
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a91what

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Apr 6, 2011
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#2
ouch that's not good let's take a look at the tune again. Did you happen to be datalogging when this occurred?
 

AUBURN1111

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Oct 17, 2000
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#7
So I tried turning the throttle stop in 1.5 turns, recalibrated TPS, burned changes seemed to idle fine with load as well as recover after acceleration. I have a new issue after idling for a minute or so RPMs jump to 3000 and stay there? I had to shut the car off, suspecting IAC valve is going crazy on me.
 

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a91what

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Mod Dude
Apr 6, 2011
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#11
the valve is still acting wierd....
look at the rpm vs idle speed. first 14% got you a 900 rpm idle then 40% did.. with a higher map signal.
auburn idle issues.PNG

either there is a valve issue or you need to be sure that there is no loose connections anywhere also the MAT sensor is not reading at all. this could be a bad electrical connection.
 

AUBURN1111

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Oct 17, 2000
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Mobile, AL
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#14
Installed new IAT sensor drove the car some, it seemed lean at idle and driving 14.6-15.9 so I enriched it a bit to get idle closer to 13.2-13.4. I notice a lot of bucking and stumbling at partial throttle 1/8th throttle range smooths out at 1/3 to 1/2 throttle. I also seem to have to use a lot of throttle and feather the clutch to get it rolling or its easy to stall. Not sure if IAT sensor affects AFRs that much hopefully I didn't get a bad one from the store? On the plus side.....it drives!!!!!!
 

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a91what

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Mod Dude
Apr 6, 2011
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#15
The mat sensor plays a large role in fuel delivery. If it is reading correctly now then it is not unreasonable for the fuel to lean out. I will look into it later bbq time right now
 

a91what

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Apr 6, 2011
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#16
After reviewing the datalog i can say you did a fine job getting the fuel adjusted and blended into the rest of the table:nice:.
do you have a datalog of you driving the car??? If you do I want to see if i can identify the source of the part throttle bucking [I am willing to put money on the fact it is fuel related (lean)]
 

5.0Thunder

Active Member
Jan 31, 2018
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#18
Good work guys. First thing I noticed when looking at that datalog image was the unchanged MAT. lol
 

AUBURN1111

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Oct 17, 2000
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Mobile, AL
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#19
same tune Ver as above 5.1.1, still have some drivability issues, hesitation, bucking at part throttle. I believe it is what you suspected and that it needs more fuel. I haven't messed with any of the tune, wanted you to look at the data logs first.
 

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