Check engine light
03-10-2016, 12:33 AM
#11
5th Gear Member
Join Date: Oct 2008
Location: CA
Posts: 2,073
It read no fault codes because when you disconnected the battery you cleared them out of the memory. You should have waited for the code reader since you spent the money on it.
So, the cel will either pop back up at some point or not, if it doesn't then it was likely just a one time thing.
The vacuum readings you got are typical, 15-20 on idle & coast, approaching zero in wide open throttle, unless you are boosted with a supercharger or turbo in which case it will go from suck to blow on WOT.
So, the cel will either pop back up at some point or not, if it doesn't then it was likely just a one time thing.
The vacuum readings you got are typical, 15-20 on idle & coast, approaching zero in wide open throttle, unless you are boosted with a supercharger or turbo in which case it will go from suck to blow on WOT.
03-10-2016, 09:37 AM
#12
Thread Starter
Join Date: Feb 2016
Location: Florida
Posts: 24
It read no fault codes because when you disconnected the battery you cleared them out of the memory. You should have waited for the code reader since you spent the money on it.
So, the cel will either pop back up at some point or not, if it doesn't then it was likely just a one time thing.
The vacuum readings you got are typical, 15-20 on idle & coast, approaching zero in wide open throttle, unless you are boosted with a supercharger or turbo in which case it will go from suck to blow on WOT.
So, the cel will either pop back up at some point or not, if it doesn't then it was likely just a one time thing.
The vacuum readings you got are typical, 15-20 on idle & coast, approaching zero in wide open throttle, unless you are boosted with a supercharger or turbo in which case it will go from suck to blow on WOT.
03-10-2016, 10:33 AM
#13
3rd Gear Member
Join Date: Nov 2006
Location: Kansas City
Posts: 960
Does your scanner show LT fuel trim and ST fuel trim?
If not, then you are going to have to wait until the light comes back on to check the code. If it does. Disconnecting the battery cleared the ECU memory.
At least you now have the reader handy for the next time.
You need to understand that a code reader is not a diagnosis. It is just a tool used to get started in the right direction. Gives you an idea of where to look instead of just completely guessing.
If not, then you are going to have to wait until the light comes back on to check the code. If it does. Disconnecting the battery cleared the ECU memory.
At least you now have the reader handy for the next time.
You need to understand that a code reader is not a diagnosis. It is just a tool used to get started in the right direction. Gives you an idea of where to look instead of just completely guessing.
Last edited by SCCAGT; 03-10-2016 at 10:37 AM.
03-10-2016, 10:52 AM
#14
Thread Starter
Join Date: Feb 2016
Location: Florida
Posts: 24
Does your scanner show LT fuel trim and ST fuel trim?
If not, then you are going to have to wait until the light comes back on to check the code. If it does. Disconnecting the battery cleared the ECU memory.
At least you now have the reader handy for the next time.
You need to understand that a code reader is not a diagnosis. It is just a tool used to get started in the right direction. Gives you an idea of where to look instead of just completely guessing.
If not, then you are going to have to wait until the light comes back on to check the code. If it does. Disconnecting the battery cleared the ECU memory.
At least you now have the reader handy for the next time.
You need to understand that a code reader is not a diagnosis. It is just a tool used to get started in the right direction. Gives you an idea of where to look instead of just completely guessing.
03-10-2016, 11:06 AM
#15
Thread Starter
Join Date: Feb 2016
Location: Florida
Posts: 24
Does your scanner show LT fuel trim and ST fuel trim?
If not, then you are going to have to wait until the light comes back on to check the code. If it does. Disconnecting the battery cleared the ECU memory.
At least you now have the reader handy for the next time.
You need to understand that a code reader is not a diagnosis. It is just a tool used to get started in the right direction. Gives you an idea of where to look instead of just completely guessing.
If not, then you are going to have to wait until the light comes back on to check the code. If it does. Disconnecting the battery cleared the ECU memory.
At least you now have the reader handy for the next time.
You need to understand that a code reader is not a diagnosis. It is just a tool used to get started in the right direction. Gives you an idea of where to look instead of just completely guessing.
umm it has a lot of fuel trims
fuel trim bank 1 long term
fuel trim bank 1 sensor 1
fuel trim bank 1 sensor 2
fuel trim bank 1 sensor 3
fuel trim bank 1 sensor 4
fuel trim bank 1 short term
fuel trim bank 2 long term
fuel trim bank 2 sensor 1
fuel trim bank 2 sensor 2
fuel trim bank 2 sensor 3
fuel trim bank 2 sensor 4
fuel trim ban 2 short term
03-10-2016, 12:36 PM
#16
3rd Gear Member
Join Date: Nov 2006
Location: Kansas City
Posts: 960
Just the ST/LT from Bank 1/2. not the sensors.
Also, if codes 171/174 or an evap code is why the light were on, it will take more than 2 start cycles for it to return. I assume by now you have started it more than twice. This is still all speculation until a code comes up, but I will still stick to 171/174. Which ends up meaning there is a vacuum leak somewhere. Odds are at the plastic upper manifold to the cylinder head.
Also, if codes 171/174 or an evap code is why the light were on, it will take more than 2 start cycles for it to return. I assume by now you have started it more than twice. This is still all speculation until a code comes up, but I will still stick to 171/174. Which ends up meaning there is a vacuum leak somewhere. Odds are at the plastic upper manifold to the cylinder head.
03-10-2016, 05:54 PM
#17
Thread Starter
Join Date: Feb 2016
Location: Florida
Posts: 24
Just the ST/LT from Bank 1/2. not the sensors.
Also, if codes 171/174 or an evap code is why the light were on, it will take more than 2 start cycles for it to return. I assume by now you have started it more than twice. This is still all speculation until a code comes up, but I will still stick to 171/174. Which ends up meaning there is a vacuum leak somewhere. Odds are at the plastic upper manifold to the cylinder head.
Also, if codes 171/174 or an evap code is why the light were on, it will take more than 2 start cycles for it to return. I assume by now you have started it more than twice. This is still all speculation until a code comes up, but I will still stick to 171/174. Which ends up meaning there is a vacuum leak somewhere. Odds are at the plastic upper manifold to the cylinder head.
Yeah I've started it probably a dozen times and I did a 0-60 yesterday and started it 2 or 3 times since then so idk if it will come back. But I'm gonna graph some of the data like intake, maf and the fuel and see from there? Just monitor the graphs and see what happens
03-10-2016, 09:26 PM
#18
Thread Starter
Join Date: Feb 2016
Location: Florida
Posts: 24
Man I just wanna say how much of a help you have been and how thankful I am for you to help me this much.
Yeah I've started it probably a dozen times and I did a 0-60 yesterday and started it 2 or 3 times since then so idk if it will come back. But I'm gonna graph some of the data like intake, maf and the fuel and see from there? Just monitor the graphs and see what happens
Yeah I've started it probably a dozen times and I did a 0-60 yesterday and started it 2 or 3 times since then so idk if it will come back. But I'm gonna graph some of the data like intake, maf and the fuel and see from there? Just monitor the graphs and see what happens
the red line is FT long term and the green is FT short term and blue is MAF rate(isnt on the 2nd photo).
it seems like the LT is staying constant at 18% no matter what rpm and then the ST fluctuates to around 5% when there is around 2500 rpm.
So im thinking that the ST is normal but shouldn't the LT be around zero too?
Last edited by stwarrior23; 03-10-2016 at 09:28 PM.
03-15-2016, 09:58 AM
#19
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
No LT should not be near zero. It usually hovers at +/- 5% to 10% depending on how long ago you reset your PCM and what's going on with the engine. A high +LT trim (Running rich) indicates your engine is constantly throwing/adding fuel to the engine, this could be anything from an O2 sensor reading lean constantly to a fuel injector leak.
A high -LT trim indicates the PCM thinks you are running really rich so it's trimming fuel back and and could also be a bad O2 sensor or MAF etc.
If it's a high -LT trim, do not drive the car, you are probably running really lean in reality from the PCM pulling fuel which means you can damage your motor.
LT at +18% constant means your PCM thinks it's running lean so it's adding fuel to compensate. In reality this just makes the car run rich. My guess is your MPG has dropped significantly and your tailpipe tips may be sooty/black? You can drive like this for a while but be aware you may eventually burn out your cats from excess fuel being thrown into them.
A high -LT trim indicates the PCM thinks you are running really rich so it's trimming fuel back and and could also be a bad O2 sensor or MAF etc.
If it's a high -LT trim, do not drive the car, you are probably running really lean in reality from the PCM pulling fuel which means you can damage your motor.
LT at +18% constant means your PCM thinks it's running lean so it's adding fuel to compensate. In reality this just makes the car run rich. My guess is your MPG has dropped significantly and your tailpipe tips may be sooty/black? You can drive like this for a while but be aware you may eventually burn out your cats from excess fuel being thrown into them.
03-15-2016, 01:57 PM
#20
3rd Gear Member
Join Date: Nov 2006
Location: Kansas City
Posts: 960
In order for the CEL to come on for 171/174, the ST/LT numbers must exceed 21 when added together. Does not matter if they are negative or positive. 21 is the magic number to turn on the light. I see that it should be on, but its not. May not quite be for a long enough period of time to trigger it. Anyway, if the light is not on, you are not in danger of damaging the engine. The cats would be getting red hot long before engine gets hurt. Not that cats are cheap, but they will go first. Lean or rich condition, they will overheat.
One thing you can do in the mean time, is get a can of brake clean and check for vacuum leaks. All you have to do is spray the gasket area between the manifold and head while the engine is running. Do this in small squirts to help nail down the location. If the engine rpm's all of a sudden change a bit while it got sprayed you found the leak area. This is the shade tree way of doing what a smoke machine does. If nothing happens, you may want to try doing it when engine is hot and cold. Since metals expand under heat, it may not be as noticeable when its hot.
But still need to see if the light comes back on for any kind of confirmation of where to start.
One thing you can do in the mean time, is get a can of brake clean and check for vacuum leaks. All you have to do is spray the gasket area between the manifold and head while the engine is running. Do this in small squirts to help nail down the location. If the engine rpm's all of a sudden change a bit while it got sprayed you found the leak area. This is the shade tree way of doing what a smoke machine does. If nothing happens, you may want to try doing it when engine is hot and cold. Since metals expand under heat, it may not be as noticeable when its hot.
But still need to see if the light comes back on for any kind of confirmation of where to start.
Last edited by SCCAGT; 03-15-2016 at 02:00 PM.
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