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Author
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Topic: Why does my car think it's high?
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BCINGUU
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Member # 2397
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posted
 
 
My 90 GT is using its altitude spark table (I know this from changing the values in the 3 spark tables, using the TwEECer RT datalogging chip). I found this out while trying to solve a hesitation / backfire on hard acceleration at low RPM (load of 100% to 110% between 1900 and 2100 rpm).
I swapped the MAP sensor with the one from my other mustang, no effect. I have also just replaced the cap, rotor, coil, distributor, ignition, and ECU. MAF output is normal.
Why does my car think it's high? Any thoughts? Is there some other altitude sensor somewhere?
[ July 28, 2004, 12:53 PM: Message edited by: BCINGUU ]
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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Cacksta
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Member # 4351
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posted
Just a thought, but i do know some cars were meant to be sold in high alt areas and come with a different timing map to adjust to the thin air. Im pretty sure there is no alt sensor in our cars so you may just be one of the unlucky high alt programmed cars? Elaborate someone?
Posts: 61 | From: San Jose, ca | Registered: Apr 2004
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Hungry Hippo
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Member # 537
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posted
too much drugs for the car ![[Cool]](cool.gif)
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05 S4 Avant(wagon)
09 C6 H/C/I
Posts: 2959 | From: east bay | Registered: Nov 2001
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BCINGUU
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Member # 2397
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posted
Nevermind, I found the problem. It was a bad ground. Somebody told me this could cause my hesitation, backfire, ignition system failure, and altitude misjudgement all at the same time, and apparently it was true! Turns out my battery was grounded only to the engine, not to the chassis. I did the ground up right, and it drives like silk now.
quote:
Originally posted by BCINGUU:
My 90 GT is using its altitude spark table (I know this from changing the values in the 3 spark tables, using the TwEECer RT datalogging chip). I found this out while trying to solve a hesitation / backfire on hard acceleration at low RPM (load of 100% to 110% between 1900 and 2100 rpm).
I swapped the MAP sensor with the one from my other mustang, no effect. I have also just replaced the cap, rotor, coil, distributor, ignition, and ECU. MAF output is normal.
Why does my car think it's high? Any thoughts? Is there some other altitude sensor somewhere?
--------------------
93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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BCINGUU
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Member # 2397
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posted
FYI, turns out there were two problems!
One was the bad ground, probably responsible for my electrical system burnout.
The other was a bad EGR gasket, responsible for the hesitation and backfire and the wrong altitude reading.
Just to let you know, in case anybody else gets this problem. Check the EGR!
[ July 29, 2004, 10:38 AM: Message edited by: BCINGUU ]
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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9lbpony
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Member # 3510
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posted
Glad you found it - I was going to suggest that maybe some of your stickers had fallen off. ![[Big Grin]](biggrin.gif)
Posts: 111 | Registered: Oct 2003
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