Tune all of a sudden running lean?
02-10-2013, 04:55 PM
#1
Tune all of a sudden running lean? Hey guys. Has anybody ever heard of a tune just all of a sudden up and running lean one day? The tune that I have in my car has been there for over a year and just the other day it started running super lean at idle like 18:1 or more. I loaded up a different tune done by somebody else and it idled back down at 14.7:1 again like it should. Loaded up the original tune and back to 18:1 or more. Anybody ever heard of something like this? Battery/alternator voltage possibly affect something like this?
02-14-2013, 06:21 AM
#3
I am not going to dispute that the wideband may not be spot on but it is damn close. The car is so lean it does not run well at all when this happens. It will not rev up when the accelerator is pressed and you can tell in the way it sounds and is running that it is being starved of fuel. It has a distinct sound, I don't know how to describe it but it is not the smooth nice sounding lopey idle.
I wasn't actually saying the numbers in the tables change but can the tune become corrupt or something along those lines while it is being used in the PCM?
If it was something else mechanical or even electrical it would be happening on all tunes across the board, changing the tune should not affect it.
I wasn't actually saying the numbers in the tables change but can the tune become corrupt or something along those lines while it is being used in the PCM?
If it was something else mechanical or even electrical it would be happening on all tunes across the board, changing the tune should not affect it.
Last edited by tording99Z28; 02-14-2013 at 06:31 AM.
02-14-2013, 06:42 AM
#5
Could a slight weather change actually affect the AFR from 14.7:1 all the way to around 18:1 at idle? I have driven the car in different weather conditions and never had this issue till now. As I said if it was something with the car like mechanical or electrical I would see this issue across all tunes correct?
Trending Topics
02-14-2013, 06:53 AM
#8
Can you explain how simply changing to a different tune then makes the problem go away? I am not saying you are wrong, if it's the car I want to fix it but I have to know where to start. In my mind if the problem is there with one tune and not another then the problem is the tune or tune file. If the problem persisted across multiple tunes then the car would be suspect.
02-14-2013, 07:36 AM
#10
FormerVendor
Join Date: Nov 2012
Location: Dyno Tuning in KY
Posts: 390
Likes: 0
Received 0 Likes
on
0 Posts
Check fuel pressure. If it ran fine before and now runs bad here are some things that could cause your problem.
Fuel pressure
MAF dirty or faulty
Map sensor
IAT sensor
O2 sensors
Start by checking those things and that will help narrow down exactly what the problem is.
Fuel pressure
MAF dirty or faulty
Map sensor
IAT sensor
O2 sensors
Start by checking those things and that will help narrow down exactly what the problem is.
02-14-2013, 07:57 AM
#12
sounds like fuel pump is going out.. my buddy had a 228r cammed t/a that ran like it had 200 hp. then he threw a pump in it and the power was back lol just a thought. maybe clean maf?
02-14-2013, 08:09 AM
#13
I guess I should have given a few more specifics to help out. It is a 3 bar SD tune so no MAF. Fuel pressure is being logged and shows 52 psi at all times which is the same as before the issue started happening. If the fuel pump was going out wouldn't the fuel pressure be less? The tune that I want in the car was done by Ed Hutchings here locally in Hampton Roads. It is the same tune that he did for the car a year ago and nothing has changed. This is the tune that one day while the car was running it just started running lean out of no where. The other tune that I mentioned was done by a different shop before I had Ed tune it and I didn't like the tune. The driveability was not as good as Ed's tune but the idle was fine so that is why I loaded it back up. With that tune it idles at 14.7:1 like it should. I put Ed's tune back in and bam back to around 18:1 again. As far as the other things mentioned like IAT and O2 sensors they are all reporting fine in HPtuners when I datalog. If they were acting up wouldn't I see some indications in my logs or not necessarily?
02-14-2013, 09:57 AM
#14
FormerVendor
Join Date: Nov 2012
Location: Dyno Tuning in KY
Posts: 390
Likes: 0
Received 0 Likes
on
0 Posts
If the o2's are working and there is fuel pressure then it would not be running 18:1 AFR. Log the o2 mV to see if they are in fact switching like they should. Or is the tune setup for full time open loop? I've seen o2's cause all sorts of issues on these cars when they go bad.
02-14-2013, 10:13 AM
#15
If the o2's are working and there is fuel pressure then it would not be running 18:1 AFR. Log the o2 mV to see if they are in fact switching like they should. Or is the tune setup for full time open loop? I've seen o2's cause all sorts of issues on these cars when they go bad.
I did a mail order calibration for him "in the late '90s", he now has a blower with 16 psi. If you need a virgin file to start with (that is what I always do) and don't have one I can email one to you. Just let me know.
02-14-2013, 03:47 PM
#17
The tune that was going lean at idle was an open loop tune. He was running race fuel some last year, and I figured the O2s would sooner or later take a poop and he was better off in OL. The tune has been fine for over a year. About 15 months actually.
When it goes lean, in the log, the IDC decreases by .3 ms. Not much, but with big injectors, it could be enough for it to tweak the A/F that much, not sure. For the time being we put it back in closed loop to see how it will act. I'm interested in if the trims swing wildly when this happens.
A little more info. He said it first happened when he let the car sit and idle for 15+ minutes. My first thought was IAT soak, but he didn't have a data log of that occurance. The data log he DID have, the one I was looking at, did not at all look like IAT soak.
So, kinda baffled myself. We'll see how it acts in closed loop and go from there.
When it goes lean, in the log, the IDC decreases by .3 ms. Not much, but with big injectors, it could be enough for it to tweak the A/F that much, not sure. For the time being we put it back in closed loop to see how it will act. I'm interested in if the trims swing wildly when this happens.
A little more info. He said it first happened when he let the car sit and idle for 15+ minutes. My first thought was IAT soak, but he didn't have a data log of that occurance. The data log he DID have, the one I was looking at, did not at all look like IAT soak.
So, kinda baffled myself. We'll see how it acts in closed loop and go from there.
02-14-2013, 04:15 PM
#18
FormerVendor
Join Date: Nov 2012
Location: Dyno Tuning in KY
Posts: 390
Likes: 0
Received 0 Likes
on
0 Posts
James, I just hung up the phone from recomending you to tune a '95 Vette. He wanted it dyno tuned.
I did a mail order calibration for him "in the late '90s", he now has a blower with 16 psi. If you need a virgin file to start with (that is what I always do) and don't have one I can email one to you. Just let me know.
I did a mail order calibration for him "in the late '90s", he now has a blower with 16 psi. If you need a virgin file to start with (that is what I always do) and don't have one I can email one to you. Just let me know.
OP I'm sure working with Ed, he will get you fixed right up.
02-19-2013, 01:05 PM
#19
Ok, so some more information here with the car. Thanks for jumping in edcmat. I put the closed loop tune in it and it does indeed bring the AFR back down to 14.7:1 or so after a minute or two but for that minute or two it is still 18:1 or so and only after I shut the car off and start it back up. I can take the car out for a short drive after starting it and it will be fine and then I will come back home. I shut the car off with it running just fine and and fire it back up and it will be 18:1 or so for that minute or two until the new closed loop tune brings it back down. Now my fear is that I have an injector not spraying or opening correctly and that particular cylinder is running lean and to compensate the PCM is adding more fuel in the other cylinders to bring the AFR back down. It still seems to be something heat related or related to cycling the key off and back on because like I said upon first startup from a cold engine everything acts normal. Not until I shut the car off and fire it back up that it shows lean. I am pulling the plugs tonight to check them and see if I can tell if a cylinder is in fact running lean.
One other note is that this all started happening around the same time that I painted my coils. I can not think of any reason why coils would cause the car to run lean but just to be sure I am borrowing another set of coils to see if it is related. The first time I started the car after doing the coils a couple of them were arcing because I got just a small dot of paint on the heat sink portion of the coil and I guess it was enough to cause an arc somehow. It did not happen for very long just on startup for a few seconds and then stopped. Anybody think of a reason why painted coils that arced briefly would cause anything like this?
One other note is that this all started happening around the same time that I painted my coils. I can not think of any reason why coils would cause the car to run lean but just to be sure I am borrowing another set of coils to see if it is related. The first time I started the car after doing the coils a couple of them were arcing because I got just a small dot of paint on the heat sink portion of the coil and I guess it was enough to cause an arc somehow. It did not happen for very long just on startup for a few seconds and then stopped. Anybody think of a reason why painted coils that arced briefly would cause anything like this?
Last edited by tording99Z28; 02-19-2013 at 01:10 PM.
02-20-2013, 01:37 PM
#20
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,604
Likes: 0
Received 6 Likes
on
6 Posts
One key question is always, is the wideband for real.
Misfires is one way for the wideband to report a value
that's way off from the real shot fuel, drawn air AFR.
The oxygen in the exhaust fools it, because the sensor
sees oxygen out, and makes a reading based on an
-assumed- exhaust oxygen to input AFR relation. Which
in turn assumes clean and complete combustion.
Misfires can be elevated by slow NBO2 response, by
some change to timing caused by weather, some new
sensitivity -to- timing, etc. Also boost makes the ignition
system work harder, maybe you've got a weak component
that is dropping out (or just marginal) at one tune's
running MAP level but is on the right side of it, with the
other.
Misfires is one way for the wideband to report a value
that's way off from the real shot fuel, drawn air AFR.
The oxygen in the exhaust fools it, because the sensor
sees oxygen out, and makes a reading based on an
-assumed- exhaust oxygen to input AFR relation. Which
in turn assumes clean and complete combustion.
Misfires can be elevated by slow NBO2 response, by
some change to timing caused by weather, some new
sensitivity -to- timing, etc. Also boost makes the ignition
system work harder, maybe you've got a weak component
that is dropping out (or just marginal) at one tune's
running MAP level but is on the right side of it, with the
other.
