85 Z28 TPI Closed Loop Problems
10-27-2010, 02:49 PM
#1
Junior Member
Thread Starter
Join Date: Apr 2010
Location: North Dakota
Posts: 43
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1985 Z28 Camaro
Engine: 385 Stroker
Transmission: 700R4
Axle/Gears: 4:11
85 Z28 TPI Closed Loop Problems
Hi Everyone,
I have a 1985 Z28 Camaro with TPI 305. It has the edelbrock TES headers and Y-pipe then I got a straight through glasspack in place of were the cat would go, then mandrel 3" under the axle out to the bumper. The A.I.R system has also been taken out. I also have a 160 thermostat.
The other day when I was driving I noticed while watching the scanner the computer is only in closed loop when the engine is under load. For example I was going down the road with engine at operating temp at about 65 MPH and the computer was in open loop but when I just barely increased the throttle to speed up it went into closed loop. then when went back to constant throttle position it went back to open loop. Is this normal? Or is the O2 sensor only getting hot enough when the engine is under load? Or is the O2 sensor faulty. It runs great by the way.
Thanks.
I have a 1985 Z28 Camaro with TPI 305. It has the edelbrock TES headers and Y-pipe then I got a straight through glasspack in place of were the cat would go, then mandrel 3" under the axle out to the bumper. The A.I.R system has also been taken out. I also have a 160 thermostat.
The other day when I was driving I noticed while watching the scanner the computer is only in closed loop when the engine is under load. For example I was going down the road with engine at operating temp at about 65 MPH and the computer was in open loop but when I just barely increased the throttle to speed up it went into closed loop. then when went back to constant throttle position it went back to open loop. Is this normal? Or is the O2 sensor only getting hot enough when the engine is under load? Or is the O2 sensor faulty. It runs great by the way.
Thanks.
10-27-2010, 09:56 PM
#2
Senior Member
Join Date: Oct 2009
Location: Pacific NW
Posts: 676
Likes: 0
Received 1 Like
on
1 Post
Car: 89 K3500 Fleetside
Engine: RAT *tbi* EBL
Transmission: TH400
Axle/Gears: 3.73-Dana 60
Re: 85 Z28 TPI Closed Loop Problems
Problem?
No, what you are seeing sounds like lean cruise or "Highway Mode".
The ECM drops active control via BLM, for pre-determined & separate AFR.
No, what you are seeing sounds like lean cruise or "Highway Mode".
The ECM drops active control via BLM, for pre-determined & separate AFR.
10-29-2010, 12:55 PM
#3
Junior Member
Thread Starter
Join Date: Apr 2010
Location: North Dakota
Posts: 43
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1985 Z28 Camaro
Engine: 385 Stroker
Transmission: 700R4
Axle/Gears: 4:11
Re: 85 Z28 TPI Closed Loop Problems
Oh its going into highway mode?
Thanks for the info!
Thanks for the info!
Thread
Thread Starter
Forum
Replies
Last Post
1992rs/ss
NW Indiana and South Chicago Suburb
12
05-19-2020 07:02 PM
1992rs/ss
Engine/Drivetrain/Suspension Parts for Sale
16
01-28-2016 09:58 PM
Sanjay
Engine/Drivetrain/Suspension Parts for Sale
1
08-12-2015 03:41 PM
