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  EFI- OX sensor op.

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Author Topic:   EFI- OX sensor op.
Bluegras
Journeyman

Posts: 29
From:
Registered: Nov 2001

posted 11-22-2001 10:47 PM     Click Here to See the Profile for Bluegras   Click Here to Email Bluegras     Edit/Delete Message   Reply w/Quote
Can't get the oxygen sensors to work full time.
Engine is rettrofitted 73-302. Shorty headers with sensors just off the outlet flanges. No starting problems, fuel press. is 38#, ECU subbed,ox sens. changed, thermostat 190, cam has a late exhaust opening profile.
How it acts: exhaust popping until more than half throttle then clears (WOT strategy coming in?). Turn ign. off and on to reset ECU, clears it for short time. Idle is rough. No useful codes. Sometimes clears and runs correct. Been running without ox sens plugged up to use the car. It runs reasonable this way but preffer the power thats really there.

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SteveLaRiviere
Administrator

Posts: 24286
From: Saco, Maine Toys: '70 Mustang Mach 1 - '72 Mustang Sprint - '94 F-150
Registered: May 99

posted 11-23-2001 12:52 PM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
Are you running any lead octane boosters? I wonder if your sensors are getting coated.

What do you mean by ECU subbed? Subbed by what?

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'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
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Bluegras
Journeyman

Posts: 29
From:
Registered: Nov 2001

posted 11-23-2001 08:47 PM     Click Here to See the Profile for Bluegras   Click Here to Email Bluegras     Edit/Delete Message   Reply w/Quote
No additives in the fuel. Gas out of the pump same as for any other car. The heads have hard seats installed.
Subbed in this case means the ECU has been replaced with another unit with the same results.
It could be that the engine being built on the loose side is passing more oil than the sensors can handle. Had long tube headers on with sensors in the collectors, then changed to the short header system to get them close to the exhaust ports, didn't help. Iv'e been chasing this for several years.

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PS65Coupe
Journeyman

Posts: 54
From: Renton, WA, USA
Registered: Dec 2000

posted 11-23-2001 11:21 PM     Click Here to See the Profile for PS65Coupe   Click Here to Email PS65Coupe     Edit/Delete Message   Reply w/Quote
You sure it's the O2 sensor? Maybe you've got a plain old vacuum leak - checked it with a vacuum guage? I fought a similar problem in a Chevy I was cursed with until I was blue in the face - turned out to be a real bad vacuum leak. (Note: Cavalier is a French word that means "Piece of Crap" ). Alternately, maybe the O2 sensor wants to be hotter. Tried a heated sensor?
Pat S

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Bluegras
Journeyman

Posts: 29
From:
Registered: Nov 2001

posted 11-24-2001 02:53 PM     Click Here to See the Profile for Bluegras   Click Here to Email Bluegras     Edit/Delete Message   Reply w/Quote
The sensors are the heated type and have voltage at the plug. I guess I'll have to remove the intake and look for something.
The vac is close to 17 Hg when running correct but drops to around 13 when in trouble.
Thanks everyone for your thoughts. I'll get it one day then let all know what I found.
This could be crosstalk/ intermittant open/short on the wireing or just about anything. Just takes a large amount of time to get to all tested.

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