L98 - Driving in Open Loop - Can It Hurt?
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Pro
Joined: Jan 2004
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From: Forney Texas
L98 - Driving in Open Loop - Can It Hurt?
I recently purchased a set of headers that were supposed to be emissions legal but they do not have the O2 sensor bungs installed. This means that I must drive approximately 15 miles to the shop to have the system welded in place.
Since my car begins each day in the open loop condition I would think the only problem would be poor fuel management. As I intend to only make a roughly 30 mile round trip I can't think of a reason this could be harmful.
I am asking you to make sure I have not overlooked anything. I spent this winter doing numerous mods and would hate to have it all go up in smoke because of my ignorance.
Thanks for your input.
90Indy
Since my car begins each day in the open loop condition I would think the only problem would be poor fuel management. As I intend to only make a roughly 30 mile round trip I can't think of a reason this could be harmful.
I am asking you to make sure I have not overlooked anything. I spent this winter doing numerous mods and would hate to have it all go up in smoke because of my ignorance.
Thanks for your input.
90Indy
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
I believe that, after a short warm up time when coolant has reached the proper temp, your ECM will detect a problem with the O2 sensor (it's absent) and go into Limp Home mode.
This will set fuel & timing curves in such a way as to protect the engine till the detected O2 sensor problem can be corrected. So I don't see how driving it to the shop will damage it but I would drive with a light foot anyway.
This will set fuel & timing curves in such a way as to protect the engine till the detected O2 sensor problem can be corrected. So I don't see how driving it to the shop will damage it but I would drive with a light foot anyway.
Team Owner
Joined: Sep 2001
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From: Athens AL
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The ECM doesnt go into limp home mode when the O2 fails, but since the O2 is so important the car will run terribly rich and you should be able to smell the fuel.
Le Mans Master
Joined: Jan 2003
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From: Portland Oregon
Originally Posted by SHINOBI-X
no to high jack a thread but when does a ECM go into "limp home mode"?
Drifting
Joined: May 1999
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From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
After startup the ECM has a minimum time it waits before it will go into closed loop. After the allotted amount of time passes, the ECM checks to see if the O2 sensor is varying the 0.45v voltage applied between terminals "D6" and "D7" (for an 88 ECM) to confirm that the O2 sensor is up to correct operating temp and working. If the ECM sees the O2 sensor circuit as open after proper coolant temp is reached and the alloted time constant has passed it will set a Code 13. if the voltage is too high a Code 45 (rich) or too low a Code 44 (lean) is set.
I agree with tjwong, I'd disconnect the O2 sensors to avoid an erroneous voltage being seen by the ECM. Driving in open loop shouldn't do you any real harm if you take it easy. The ECM is expected to operate in open loop the first 2 minutes or so of operation and initial driving. Longer than that if the coolant hasn't reached the prerequisite closed loop operating temp. Afterwards just clear the Code 13 and you should be good to go.
I agree with tjwong, I'd disconnect the O2 sensors to avoid an erroneous voltage being seen by the ECM. Driving in open loop shouldn't do you any real harm if you take it easy. The ECM is expected to operate in open loop the first 2 minutes or so of operation and initial driving. Longer than that if the coolant hasn't reached the prerequisite closed loop operating temp. Afterwards just clear the Code 13 and you should be good to go.
Race Director
Joined: Dec 2000
Posts: 17,551
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From: El Paso Texas
Shouldn't hurt anything for 15 miles, but if you're really concerned, just flatbed the car to the shop. Most tow services charge about $2 per loaded mile plus a hookup charge. At most you're looking probably $60. Cheaper than damaging something, even though that's unlikely.
Cheap peace of mind.
Cheap peace of mind.
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