PCM Reset Question
Thread Starter
Registered User
Joined: Sep 2018
Posts: 13
From: Arizona
PCM Reset Question
Hello Everyone,
I recently had Long Tube headers installed on my car and reset the PCM After hooking up the O2 Sensors and what not.
The car idles rough and once it is warmed up drives rough unless I hit the gas. Is this normal after a reset? If so, how long before it will go back to normal? Any help would be greatly appreciated.
The Pcm is from Pcmforless if that affects anything.
I recently had Long Tube headers installed on my car and reset the PCM After hooking up the O2 Sensors and what not.
The car idles rough and once it is warmed up drives rough unless I hit the gas. Is this normal after a reset? If so, how long before it will go back to normal? Any help would be greatly appreciated.
The Pcm is from Pcmforless if that affects anything.
Administrator
Joined: Nov 1998
Posts: 71,086
From: Hell was full so they sent me to NJ
Re: PCM Reset Question
You really need to add a “signature” with basic info about the car.
Removing the power from the PCM “resets” it, clearing the long term fuel corrections. In order for the PCM to “learn” it has to enter closed loop. To do that, three things have to happen - the engine has to run for about 3-1/2 minutes; the coolant temperature has to reach about 140°F; the O2 sensors have to get hot enough to work (about 600°F). A problem with an O2 sensor or wire can prevent it from entering closed loop.
Once it enters closed loop, it should learn fairly quickly. But there are numerous “cells” that have to be relearned, each cell based on specific RPM and MAP (engine load) values. For example, the idle A/F ratio is controlled by cell #16. Letting it idle for a few minutes should allow that cell to stabilize. But some of the other 15 cells used while driving may take days if you don’t happen to hit the specific range of RPM and MAP they control.
With long tube header install, I would check the O2 sensor extensions, check the sensors for contamination, check the exhaust for leaks before the sensors. Then there’s the possibility a spark plug was cracked, a plug wire was not fastened correctly or crossed, or a wire burned or arcing on the headers. Do you still run EGR and AIR?
Best way to check is to run a PCM data log using the free software available, but to recommend that we need to know the details of the car/engine.
https://www.camaroz28.com/forums/lt1...nature-879835/
Removing the power from the PCM “resets” it, clearing the long term fuel corrections. In order for the PCM to “learn” it has to enter closed loop. To do that, three things have to happen - the engine has to run for about 3-1/2 minutes; the coolant temperature has to reach about 140°F; the O2 sensors have to get hot enough to work (about 600°F). A problem with an O2 sensor or wire can prevent it from entering closed loop.
Once it enters closed loop, it should learn fairly quickly. But there are numerous “cells” that have to be relearned, each cell based on specific RPM and MAP (engine load) values. For example, the idle A/F ratio is controlled by cell #16. Letting it idle for a few minutes should allow that cell to stabilize. But some of the other 15 cells used while driving may take days if you don’t happen to hit the specific range of RPM and MAP they control.
With long tube header install, I would check the O2 sensor extensions, check the sensors for contamination, check the exhaust for leaks before the sensors. Then there’s the possibility a spark plug was cracked, a plug wire was not fastened correctly or crossed, or a wire burned or arcing on the headers. Do you still run EGR and AIR?
Best way to check is to run a PCM data log using the free software available, but to recommend that we need to know the details of the car/engine.
https://www.camaroz28.com/forums/lt1...nature-879835/
Last edited by Injuneer; Sep 11, 2018 at 09:40 AM.
Thread Starter
Registered User
Joined: Sep 2018
Posts: 13
From: Arizona
Re: PCM Reset Question
Sorry, I am new to the site! There is no exhaust leak. I will check the plugs and wires today. The EGR and Air components are there but cannot be hooked up to the headers. I am going to get block off plates for those.
The car is an LT1 trans am. The only mods are the Full exhaust and the Pcmforless tune (I got the tune before the exhaust because I went from 2.73 gears to 3.23).
Could it be that I need a new tune?
The car is an LT1 trans am. The only mods are the Full exhaust and the Pcmforless tune (I got the tune before the exhaust because I went from 2.73 gears to 3.23).
Could it be that I need a new tune?
Administrator
Joined: Nov 1998
Posts: 71,086
From: Hell was full so they sent me to NJ
Re: PCM Reset Question
The upgraded exhaust improves the engine's breathing. The MAF sensor picks up the increase inlet air flow, so the tune isn’t critical. When did you get the pcmforless tune? Seems there has been some negative feedback after Brian stopped doing the mail order tunes.
Are you saying the headers don't have EGR and AIR connections? Removing the AIR system can extend the O2 sensor heat up time, because you're relying mostly on the sensor heater element.
You can leave the EGR in place and just use a single plate on the diamond shaped flange on the intake manifold, or remove the EGR valve and get a 2 plate kit. Was EGR tuned out of the PCM?
Did you check the header flanges for flatness? If they aren’t flat they're going to leak.
The data log software is a good diagnostic tool (and it’s free download):
https://www.camaroz28.com/forums/com...95-lt1-874306/
Are you saying the headers don't have EGR and AIR connections? Removing the AIR system can extend the O2 sensor heat up time, because you're relying mostly on the sensor heater element.
You can leave the EGR in place and just use a single plate on the diamond shaped flange on the intake manifold, or remove the EGR valve and get a 2 plate kit. Was EGR tuned out of the PCM?
Did you check the header flanges for flatness? If they aren’t flat they're going to leak.
The data log software is a good diagnostic tool (and it’s free download):
https://www.camaroz28.com/forums/com...95-lt1-874306/
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