5.3 swap possible MAF or O2 sensor issue?
10-03-2016, 02:23 PM
#1
5.3 swap possible MAF or O2 sensor issue? Long story short, I have a 5.3/4l60e swapped s10 blazer. With the MAF and the brand new O2 sensors hooked up it idles fine for about a minute and then starts chugging and running terribly, If I unplug the O2 sensors it idles fine or if I keep the O2 sensors plugged in and unplug the MAF it also idle fine. I can literally unplug the MAF and listen to it idle perfect immediately, once its plugged back in it runs poorly again. I do have an exhaust leak near the collector gasket on the passenger side that isn't far at all from the O2 sensor but I would assume it would still run OK. With Maf plugged in and O2 sensors unplugged I do not trip a MAF code just missing O2 sensor codes. Any suggestions at all? Will a dirty or bad MAF ALWAYS throw a code? Thank you guys I really appreciate any feedback and suggestions.
10-04-2016, 10:24 AM
#4
You usually need to give folks 24 hours for a full set of views. A lot of people won't see your post until the morning email updates come out...
No. It will read a lower volume of air coming in to the engine and (at times) the PCM will compensate by trimming the fuel.
Are you getting different behavior when the engine is cold vs. when it is up to full temperature? (The PCM should use different methodology for calculating air/fuel at those times.)
No. It will read a lower volume of air coming in to the engine and (at times) the PCM will compensate by trimming the fuel.
Are you getting different behavior when the engine is cold vs. when it is up to full temperature? (The PCM should use different methodology for calculating air/fuel at those times.)
10-04-2016, 10:32 AM
#5
You usually need to give folks 24 hours for a full set of views. A lot of people won't see your post until the morning email updates come out...
No. It will read a lower volume of air coming in to the engine and (at times) the PCM will compensate by trimming the fuel.
Are you getting different behavior when the engine is cold vs. when it is up to full temperature? (The PCM should use different methodology for calculating air/fuel at those times.)
No. It will read a lower volume of air coming in to the engine and (at times) the PCM will compensate by trimming the fuel.
Are you getting different behavior when the engine is cold vs. when it is up to full temperature? (The PCM should use different methodology for calculating air/fuel at those times.)
I honestly have not allowed it to get very warm with everything hooked up since it just starts chugging and idling very very bad after a minute or so of idling.
10-04-2016, 11:22 AM
#6
I'd try warming the engine up with the MAF unplugged, so it behaves. Then, turn it off, plug the MAF back in and see what happens.
Have you also had a chance to put the PCM through the relearn procedure? If not, that could also be why things are off.
Have you also had a chance to put the PCM through the relearn procedure? If not, that could also be why things are off.
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10-04-2016, 11:48 AM
#8
The PCM needs to go through the "relearn" process every time sensors change or get fixed on the car in order to optimize the combustion for its new state. If you have just swapped the engine, (particularly if you have changed some sensors in the process) things could be off. I don't remember what the process is exactly, but its something like the car needs to be driven at 35mph for several minutes for all of the process to happen. You'd of course need all of the sensors plugged in to do this.
You might search for "relearn" in the context of swaps. It seems that this is a typical issue after a swap.
10-04-2016, 01:24 PM
#9
So, it sounds like your problem is when the engine is running in closed loop: http://www.enginebasics.com/EFI%20Tu...Loop%20o2.html
The PCM needs to go through the "relearn" process every time sensors change or get fixed on the car in order to optimize the combustion for its new state. If you have just swapped the engine, (particularly if you have changed some sensors in the process) things could be off. I don't remember what the process is exactly, but its something like the car needs to be driven at 35mph for several minutes for all of the process to happen. You'd of course need all of the sensors plugged in to do this.
You might search for "relearn" in the context of swaps. It seems that this is a typical issue after a swap.
The PCM needs to go through the "relearn" process every time sensors change or get fixed on the car in order to optimize the combustion for its new state. If you have just swapped the engine, (particularly if you have changed some sensors in the process) things could be off. I don't remember what the process is exactly, but its something like the car needs to be driven at 35mph for several minutes for all of the process to happen. You'd of course need all of the sensors plugged in to do this.
You might search for "relearn" in the context of swaps. It seems that this is a typical issue after a swap.
10-04-2016, 06:31 PM
#10
Here are some procedures if you don't want to leave the driveway:
http://www.gmforum.com/howto/1998SM/...procedures.pdf
I understand that if you just take it for a 20 minute drive at mid-speeds, that should get everything set as well.
I suspect the Idle Learn Procedure is of most interest to you here. My 1999 factory service manual has slightly different times (5 minutes vs. 10 minutes) than this document but also indicates that the engine needs to be up to operating temperature before starting. Maybe that's why there is the difference?
10-04-2016, 07:06 PM
#11
More than that. If you disconnect the power for too long, that can also cause a condition where you need to run the procedure.
Here are some procedures if you don't want to leave the driveway:
http://www.gmforum.com/howto/1998SM/...procedures.pdf
I understand that if you just take it for a 20 minute drive at mid-speeds, that should get everything set as well.
I suspect the Idle Learn Procedure is of most interest to you here. My 1999 factory service manual has slightly different times (5 minutes vs. 10 minutes) than this document but also indicates that the engine needs to be up to operating temperature before starting. Maybe that's why there is the difference?
Here are some procedures if you don't want to leave the driveway:
http://www.gmforum.com/howto/1998SM/...procedures.pdf
I understand that if you just take it for a 20 minute drive at mid-speeds, that should get everything set as well.
I suspect the Idle Learn Procedure is of most interest to you here. My 1999 factory service manual has slightly different times (5 minutes vs. 10 minutes) than this document but also indicates that the engine needs to be up to operating temperature before starting. Maybe that's why there is the difference?
10-04-2016, 07:55 PM
#12
So... Not to make this anymore confusing but I decided to do a little test.
I cleared all codes and hooked everything up, with the engine warmed up it idled poorly like it has a big cam and the passenger side exhaust started to smoke.
Disconnected ONLY the passenger side O2 sensor and started it back up and it idled great.
Reconnected the passenger side and disconnected the drivers side and it ran great.
I THOUGHT I was going to narrow it down to a single bad O2 sensor but that doesn't seem to be the case. Keep in mine that it also idles and revs fine with the MAF disconnected, I understand the idle relearn but would that have any affect on what the truck is doing at this point?
I cleared all codes and hooked everything up, with the engine warmed up it idled poorly like it has a big cam and the passenger side exhaust started to smoke.
Disconnected ONLY the passenger side O2 sensor and started it back up and it idled great.
Reconnected the passenger side and disconnected the drivers side and it ran great.
I THOUGHT I was going to narrow it down to a single bad O2 sensor but that doesn't seem to be the case. Keep in mine that it also idles and revs fine with the MAF disconnected, I understand the idle relearn but would that have any affect on what the truck is doing at this point?
10-05-2016, 10:05 PM
#17
I still have not found the relearn procedure for the 5.3 but I finally got a chance to drive the truck with the MAF disconnected and only the O2 sensors connected. The truck drove fine for about 5 miles, then it started to cut out and felt like it was out of gas and lost ALL power until I pulled over, disconnected the O2 sensors again and reconnected the MAF then it ran great.
10-25-2016, 06:57 PM
#18
Well... Got a new ECU from Kenny Cash that did my harness just to test out. Put it in, hooked up the battery and it started and died and then after restart idling funny and seemed to be decent but smelled pretty rich. I took it around the block and it almost died on me half way around, so I guess that eliminates any ECU tuning issues. Still runs good decent with the O2s disconnected but just feels like it is losing some power with them disconnected. I am so lost on this whole thing and I cannot find anyone local to do some logging, does anyone have a tuner/scanner they recommend to log my system?
The Regional Forums are also a good place to check for that kind of thing.
10-25-2016, 10:24 PM
#20
You're right buddy, I just updated it lol. I'm in Deltona Florida. I have debated buying a knock off Tech 2 scanner but even after I spent $300 on that I might as well buy an HP tuner scanner and I can buy a credit later to tune it, or have someone else use it and tune it.