This is topic Why does my car think it's high? in forum Tech Talk at Northern California Ford Owners  .


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Posted by BCINGUU (Member # 2397) on :
 
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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Posted by Cacksta (Member # 4351) on :
 
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?
 

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Posted by HungryHippo (Member # 537) on :
 
too much drugs for the car
 

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Posted by BCINGUU (Member # 2397) on :
 
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.

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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?

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Posted by BCINGUU (Member # 2397) on :
 
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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Posted by 9lbpony (Member # 3510) on :
 
Glad you found it - I was going to suggest that maybe some of your stickers had fallen off.
 

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