Bogging and sputtering when cold
Launching!
Joined: Apr 2019
Posts: 206
Likes: 11
From: Bay area
Could a dirty k&n filter cause a lot of issues?
TECH Regular
Joined: Dec 2005
Posts: 437
Likes: 9
From: Indianapolis
A couple things here:
You need to isolate some things first and do one thing at a time.
Your fuel pressure should be around 58 to 60 PSI at all times when the engine is running, during key on you'll see it prime to about 60 then back off a bit when the pump stops running, this will be audible. The PSI should stay relatively steady for a couple of minutes, if you are seeing it drop at the rail immediately after priming then you either have a bad check valve, a leaking injector, or a hose may be split or leaking in the pump assembly. You dropping PSI during driving is not a good sign and if you are confident isn't an error in monitoring, will be an issue sooner or later. Replacing anything to do with the pump should be done in an assembly like racetronix or similar, you don't risk having to drop the tank or go through cutting a hatch to replace a single part and have the supporting parts fail and go back through the whole thing again, I've done it, it's not fun. In this scenario it could be the problem or it could be an unrelated thing for now that will be an issue later when the pump finally starts failing more. Keep it in mind but it's not a smoking gun yet.
Your MAF being oily is a concern as well. Sometimes cleaning can work, other times damage is done to the sensor and it cannot be cleaned and read properly again. If there was oil on it then it was from the filter, no question there. Blowby cannot make it that far into the intake, the oil you see is from the PCV system that dumps the system right into the intake right by the throttle body. Sure your catch can will help keep it down but it's not perfect, especially if it's not optimally routed, there is a sticky on the forums about what I'm talking about. I have a catch can, and again it helps but some oil still does make it past it. Only way that thing is getting contaminated is via the filter, the engine pulls too much vacuum for anything to get reverse out the intake. Quick free way to check if the MAF is a problem is to unplug it and see how it runs, the PCM will rely only on the fuel map and saved fuel trims, if it runs great then the MAF is poisoning the calculation. You'll get a SES light but it won't harm anything and will clear once plugged back in. If it was me I would start here as this can explain all your symptoms so far.
Your fuel trims can be deceptive here as well. Fuel trims are only adjusted after you have hit closed loop at operating temp which I believe is about 160 F, during a cold start it will apply the last learned long term trim until you hit that temp. A general rule here is anything 7 or 8% or more on long term trims can be a symptom of an issue like a vacuum leak or fuel system problem. What I think you should look at is your O2 sensor readings, those will tell you immediately if it is running too rich or too lean and you should look at them real time, narrow band O2s are only accurate at stoich, a wideband is not needed here as the intended use for a wideband is accuracy at all ranges including WOT which is not stoich, also they are used in your fueling calculation by the PCM so they absolutely matter. If you need a guide look up "South Main Auto Oxygen Sensor" in the You Tubes and you'll see the correct process to help isolate potential fuel issues with them as well as finding vacuum leaks with spraying brake cleaner and seeing if the O2s see a rich condition. Remember too that intake leaks can seal up as the engine heat soaks and expands, so you could have an only cold leak that goes away on warm up.
With what you are saying the issue goes away once you hit closed loop and the fueling is adjusted. Your MAF fits too well so far out of the things you mentioned. I'd start by unplugging the MAF and see if your problems resolve or lessen, if they do you have a MAF that needs to be replaced and a filter as well to be safe. If nothing changes I would start looking at O2 data and vacuum leaks, if you verify everything is good there then I'd start taking a peak into your fuel system, by the time you hit the fueling then I'd think you'd have found another clue that would lead you to what the issue is. Also if your fuel pressure is really fluctuating like noted then you will be replacing the pump sooner or later, I'm just not convinced it's your "right now" problem, but if you want to tackle this now then you'll still be fixing an issue with your car. There is a sticky in the fueling section that has a walk though for the hatch method and how to swap the pump and in take hoses, also if you buy a kit I know my racetronix pump came with instructions.
Good luck.
You need to isolate some things first and do one thing at a time.
Your fuel pressure should be around 58 to 60 PSI at all times when the engine is running, during key on you'll see it prime to about 60 then back off a bit when the pump stops running, this will be audible. The PSI should stay relatively steady for a couple of minutes, if you are seeing it drop at the rail immediately after priming then you either have a bad check valve, a leaking injector, or a hose may be split or leaking in the pump assembly. You dropping PSI during driving is not a good sign and if you are confident isn't an error in monitoring, will be an issue sooner or later. Replacing anything to do with the pump should be done in an assembly like racetronix or similar, you don't risk having to drop the tank or go through cutting a hatch to replace a single part and have the supporting parts fail and go back through the whole thing again, I've done it, it's not fun. In this scenario it could be the problem or it could be an unrelated thing for now that will be an issue later when the pump finally starts failing more. Keep it in mind but it's not a smoking gun yet.
Your MAF being oily is a concern as well. Sometimes cleaning can work, other times damage is done to the sensor and it cannot be cleaned and read properly again. If there was oil on it then it was from the filter, no question there. Blowby cannot make it that far into the intake, the oil you see is from the PCV system that dumps the system right into the intake right by the throttle body. Sure your catch can will help keep it down but it's not perfect, especially if it's not optimally routed, there is a sticky on the forums about what I'm talking about. I have a catch can, and again it helps but some oil still does make it past it. Only way that thing is getting contaminated is via the filter, the engine pulls too much vacuum for anything to get reverse out the intake. Quick free way to check if the MAF is a problem is to unplug it and see how it runs, the PCM will rely only on the fuel map and saved fuel trims, if it runs great then the MAF is poisoning the calculation. You'll get a SES light but it won't harm anything and will clear once plugged back in. If it was me I would start here as this can explain all your symptoms so far.
Your fuel trims can be deceptive here as well. Fuel trims are only adjusted after you have hit closed loop at operating temp which I believe is about 160 F, during a cold start it will apply the last learned long term trim until you hit that temp. A general rule here is anything 7 or 8% or more on long term trims can be a symptom of an issue like a vacuum leak or fuel system problem. What I think you should look at is your O2 sensor readings, those will tell you immediately if it is running too rich or too lean and you should look at them real time, narrow band O2s are only accurate at stoich, a wideband is not needed here as the intended use for a wideband is accuracy at all ranges including WOT which is not stoich, also they are used in your fueling calculation by the PCM so they absolutely matter. If you need a guide look up "South Main Auto Oxygen Sensor" in the You Tubes and you'll see the correct process to help isolate potential fuel issues with them as well as finding vacuum leaks with spraying brake cleaner and seeing if the O2s see a rich condition. Remember too that intake leaks can seal up as the engine heat soaks and expands, so you could have an only cold leak that goes away on warm up.
With what you are saying the issue goes away once you hit closed loop and the fueling is adjusted. Your MAF fits too well so far out of the things you mentioned. I'd start by unplugging the MAF and see if your problems resolve or lessen, if they do you have a MAF that needs to be replaced and a filter as well to be safe. If nothing changes I would start looking at O2 data and vacuum leaks, if you verify everything is good there then I'd start taking a peak into your fuel system, by the time you hit the fueling then I'd think you'd have found another clue that would lead you to what the issue is. Also if your fuel pressure is really fluctuating like noted then you will be replacing the pump sooner or later, I'm just not convinced it's your "right now" problem, but if you want to tackle this now then you'll still be fixing an issue with your car. There is a sticky in the fueling section that has a walk though for the hatch method and how to swap the pump and in take hoses, also if you buy a kit I know my racetronix pump came with instructions.
Good luck.
Thread Starter
TECH Regular
Joined: Feb 2005
Posts: 400
Likes: 2
A couple things here:
You need to isolate some things first and do one thing at a time.
Your fuel pressure should be around 58 to 60 PSI at all times when the engine is running, during key on you'll see it prime to about 60 then back off a bit when the pump stops running, this will be audible. The PSI should stay relatively steady for a couple of minutes, if you are seeing it drop at the rail immediately after priming then you either have a bad check valve, a leaking injector, or a hose may be split or leaking in the pump assembly. You dropping PSI during driving is not a good sign and if you are confident isn't an error in monitoring, will be an issue sooner or later. Replacing anything to do with the pump should be done in an assembly like racetronix or similar, you don't risk having to drop the tank or go through cutting a hatch to replace a single part and have the supporting parts fail and go back through the whole thing again, I've done it, it's not fun. In this scenario it could be the problem or it could be an unrelated thing for now that will be an issue later when the pump finally starts failing more. Keep it in mind but it's not a smoking gun yet.
Your MAF being oily is a concern as well. Sometimes cleaning can work, other times damage is done to the sensor and it cannot be cleaned and read properly again. If there was oil on it then it was from the filter, no question there. Blowby cannot make it that far into the intake, the oil you see is from the PCV system that dumps the system right into the intake right by the throttle body. Sure your catch can will help keep it down but it's not perfect, especially if it's not optimally routed, there is a sticky on the forums about what I'm talking about. I have a catch can, and again it helps but some oil still does make it past it. Only way that thing is getting contaminated is via the filter, the engine pulls too much vacuum for anything to get reverse out the intake. Quick free way to check if the MAF is a problem is to unplug it and see how it runs, the PCM will rely only on the fuel map and saved fuel trims, if it runs great then the MAF is poisoning the calculation. You'll get a SES light but it won't harm anything and will clear once plugged back in. If it was me I would start here as this can explain all your symptoms so far.
Your fuel trims can be deceptive here as well. Fuel trims are only adjusted after you have hit closed loop at operating temp which I believe is about 160 F, during a cold start it will apply the last learned long term trim until you hit that temp. A general rule here is anything 7 or 8% or more on long term trims can be a symptom of an issue like a vacuum leak or fuel system problem. What I think you should look at is your O2 sensor readings, those will tell you immediately if it is running too rich or too lean and you should look at them real time, narrow band O2s are only accurate at stoich, a wideband is not needed here as the intended use for a wideband is accuracy at all ranges including WOT which is not stoich, also they are used in your fueling calculation by the PCM so they absolutely matter. If you need a guide look up "South Main Auto Oxygen Sensor" in the You Tubes and you'll see the correct process to help isolate potential fuel issues with them as well as finding vacuum leaks with spraying brake cleaner and seeing if the O2s see a rich condition. Remember too that intake leaks can seal up as the engine heat soaks and expands, so you could have an only cold leak that goes away on warm up.
With what you are saying the issue goes away once you hit closed loop and the fueling is adjusted. Your MAF fits too well so far out of the things you mentioned. I'd start by unplugging the MAF and see if your problems resolve or lessen, if they do you have a MAF that needs to be replaced and a filter as well to be safe. If nothing changes I would start looking at O2 data and vacuum leaks, if you verify everything is good there then I'd start taking a peak into your fuel system, by the time you hit the fueling then I'd think you'd have found another clue that would lead you to what the issue is. Also if your fuel pressure is really fluctuating like noted then you will be replacing the pump sooner or later, I'm just not convinced it's your "right now" problem, but if you want to tackle this now then you'll still be fixing an issue with your car. There is a sticky in the fueling section that has a walk though for the hatch method and how to swap the pump and in take hoses, also if you buy a kit I know my racetronix pump came with instructions.
Good luck.
You need to isolate some things first and do one thing at a time.
Your fuel pressure should be around 58 to 60 PSI at all times when the engine is running, during key on you'll see it prime to about 60 then back off a bit when the pump stops running, this will be audible. The PSI should stay relatively steady for a couple of minutes, if you are seeing it drop at the rail immediately after priming then you either have a bad check valve, a leaking injector, or a hose may be split or leaking in the pump assembly. You dropping PSI during driving is not a good sign and if you are confident isn't an error in monitoring, will be an issue sooner or later. Replacing anything to do with the pump should be done in an assembly like racetronix or similar, you don't risk having to drop the tank or go through cutting a hatch to replace a single part and have the supporting parts fail and go back through the whole thing again, I've done it, it's not fun. In this scenario it could be the problem or it could be an unrelated thing for now that will be an issue later when the pump finally starts failing more. Keep it in mind but it's not a smoking gun yet.
Your MAF being oily is a concern as well. Sometimes cleaning can work, other times damage is done to the sensor and it cannot be cleaned and read properly again. If there was oil on it then it was from the filter, no question there. Blowby cannot make it that far into the intake, the oil you see is from the PCV system that dumps the system right into the intake right by the throttle body. Sure your catch can will help keep it down but it's not perfect, especially if it's not optimally routed, there is a sticky on the forums about what I'm talking about. I have a catch can, and again it helps but some oil still does make it past it. Only way that thing is getting contaminated is via the filter, the engine pulls too much vacuum for anything to get reverse out the intake. Quick free way to check if the MAF is a problem is to unplug it and see how it runs, the PCM will rely only on the fuel map and saved fuel trims, if it runs great then the MAF is poisoning the calculation. You'll get a SES light but it won't harm anything and will clear once plugged back in. If it was me I would start here as this can explain all your symptoms so far.
Your fuel trims can be deceptive here as well. Fuel trims are only adjusted after you have hit closed loop at operating temp which I believe is about 160 F, during a cold start it will apply the last learned long term trim until you hit that temp. A general rule here is anything 7 or 8% or more on long term trims can be a symptom of an issue like a vacuum leak or fuel system problem. What I think you should look at is your O2 sensor readings, those will tell you immediately if it is running too rich or too lean and you should look at them real time, narrow band O2s are only accurate at stoich, a wideband is not needed here as the intended use for a wideband is accuracy at all ranges including WOT which is not stoich, also they are used in your fueling calculation by the PCM so they absolutely matter. If you need a guide look up "South Main Auto Oxygen Sensor" in the You Tubes and you'll see the correct process to help isolate potential fuel issues with them as well as finding vacuum leaks with spraying brake cleaner and seeing if the O2s see a rich condition. Remember too that intake leaks can seal up as the engine heat soaks and expands, so you could have an only cold leak that goes away on warm up.
With what you are saying the issue goes away once you hit closed loop and the fueling is adjusted. Your MAF fits too well so far out of the things you mentioned. I'd start by unplugging the MAF and see if your problems resolve or lessen, if they do you have a MAF that needs to be replaced and a filter as well to be safe. If nothing changes I would start looking at O2 data and vacuum leaks, if you verify everything is good there then I'd start taking a peak into your fuel system, by the time you hit the fueling then I'd think you'd have found another clue that would lead you to what the issue is. Also if your fuel pressure is really fluctuating like noted then you will be replacing the pump sooner or later, I'm just not convinced it's your "right now" problem, but if you want to tackle this now then you'll still be fixing an issue with your car. There is a sticky in the fueling section that has a walk though for the hatch method and how to swap the pump and in take hoses, also if you buy a kit I know my racetronix pump came with instructions.
Good luck.
TECH Regular
Joined: Dec 2005
Posts: 437
Likes: 9
From: Indianapolis
Replacing the car fixes everything too, lol. Have fun with it man.
