Could a bad o2 sensor....
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Could a bad o2 sensor....
Cause the car to be running rich all the time?
I just took the car out for the first time this year, started right u, runs fine, but seems a bit on the rich side, my A/F gauge is pegged at 100% rich al the time. Not sure if the gage is bad, or the O2 is mezzed up.
My FuelPressure Gauge shows the FP changing from normal to WOT, so that seems to be working good.
Thanks in advance.
I just took the car out for the first time this year, started right u, runs fine, but seems a bit on the rich side, my A/F gauge is pegged at 100% rich al the time. Not sure if the gage is bad, or the O2 is mezzed up.
My FuelPressure Gauge shows the FP changing from normal to WOT, so that seems to be working good.
Thanks in advance.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
The one time I had a bad 02 I got a lean mixture error code. So I guess it depends on the voltage reading the 02 was sending when it died.
A bad 02 won't set any code, but you should get a lean or rich error code if your 85 system is the same as my 86.
You can try jumping the A&B terminals of the ALDL to see if the system is going closed loop. One flash per second indicates closed loop and faster flashes indicates open loop (if memory serves).
Jake
A bad 02 won't set any code, but you should get a lean or rich error code if your 85 system is the same as my 86.
You can try jumping the A&B terminals of the ALDL to see if the system is going closed loop. One flash per second indicates closed loop and faster flashes indicates open loop (if memory serves).
Jake
Le Mans Master
Joined: Jun 2002
Posts: 6,097
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From: High Plains Drifter Fayetteville, AR
Originally Posted by JAKE
You can try jumping the A&B terminals of the ALDL to see if the system is going closed loop. One flash per second indicates closed loop and faster flashes indicates open loop (if memory serves).
Jake
Jake
Just to correct, that is backwards. The SES light will flash slowly in open loop. When the car goes closed loop and feedback from the O2 is used by the ECM, the SES light will flash with the transitions from lean to rich. A properly working O2 with constantly transition from rich to lean and back again.
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Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Yeah I had the O2 replaced 3 years ago,and I have a heated Bosch O2 I haven't installed yet since getting the headers, so I'll probably put that on. Ill mess with it this weekend.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by JCAIRE2
Just to correct, that is backwards. The SES light will flash slowly in open loop. When the car goes closed loop and feedback from the O2 is used by the ECM, the SES light will flash with the transitions from lean to rich. A properly working O2 with constantly transition from rich to lean and back again.
In closed loop the SES light will flash at a rate of 1 time per second and in open loop it will flash faster, which, according to the Shop Manual, will be at two and one-half times per second.
Here's the quote: "If the Diagnostic terminal is grounded with the engine running, the system will enter the Field Service mode. In this mode, the SERVICE ENGINE SOON" light will show whether the system is in Open or Closed Loop.
In Open Loop the "SERVICE ENGINE SOON" light flashes two and one-half times per second.
In "Closed Loop", the light flashes once per second: . . ."
Jake
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
Man, you guys are making me dizzy. 
Now the way I read these posts you guys are agreeing on opposite things. 
JAKE, I think you're backwards, JCAIRE2 is correct.
Open Loop - O2 Sensors too cool to work, ECM ignoring them - SLOW flash...1 per second.
Closed Loop - O2 being used by ECM - Fast inconsistent flash, light on for RICH O2 reading.
Originally Posted by JCAIRE2
Just to correct, that is backwards. The SES light will flash slowly in open loop. When the car goes closed loop and feedback from the O2 is used by the ECM, the SES light will flash with the transitions from lean to rich.
Originally Posted by JAKE
In closed loop the SES light will flash at a rate of 1 time per second and in open loop it will flash faster, which, according to the Shop Manual, will be at two and one-half times per second.
JAKE, I think you're backwards, JCAIRE2 is correct. Open Loop - O2 Sensors too cool to work, ECM ignoring them - SLOW flash...1 per second.
Closed Loop - O2 being used by ECM - Fast inconsistent flash, light on for RICH O2 reading.
Last edited by Atok; May 21, 2005 at 08:49 AM. Reason: spelling
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Originally Posted by Atok
Man, you guys are making me dizzy.
Now the way I read these posts you guys are agreeing on opposite things. JAKE, I think you're backwards, JCAIRE2 is correct.
Open Loop - O2 Sensors too cool to work, ECM ignoring them - SLOW flash...1 per second.
Closed Loop - O2 being used by ECM - Fast inconsistent flash, light on for RICH O2 reading.
Now the way I read these posts you guys are agreeing on opposite things.
JAKE, I think you're backwards, JCAIRE2 is correct. Open Loop - O2 Sensors too cool to work, ECM ignoring them - SLOW flash...1 per second.
Closed Loop - O2 being used by ECM - Fast inconsistent flash, light on for RICH O2 reading.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by Atok
Man, you guys are making me dizzy.
Now the way I read these posts you guys are agreeing on opposite things. JAKE, I think you're backwards, JCAIRE2 is correct.
Open Loop - O2 Sensors too cool to work, ECM ignoring them - SLOW flash...1 per second.
Closed Loop - O2 being used by ECM - Fast inconsistent flash, light on for RICH O2 reading.
Now the way I read these posts you guys are agreeing on opposite things.
JAKE, I think you're backwards, JCAIRE2 is correct. Open Loop - O2 Sensors too cool to work, ECM ignoring them - SLOW flash...1 per second.
Closed Loop - O2 being used by ECM - Fast inconsistent flash, light on for RICH O2 reading.
OPEN = FAST
CLOSED = SLOW
OPEN = Two and one half times per second which means FAST
CLOSED = One time per second which means SLOW
Now, this info is from the 86 Shop Manual, but if different years flash differently, well, I can't be held responsible for that.
Any questions? LOL
Jake