Misfires and lean codes

rgorke

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Thanks again to Joe for pointing me, and countless others, to misfires. I finally figured out how to check for misfires using my iPhone app diagnostic tools. And before I get yelled at: 04 V8 with all the bells and whistles, 217k miles. All plastics changed out and new coils in mid 2016. Been getting P0171 and P0174 and occasional P2195 and P2197 codes.

It appears that for the first 15-20 mins of the car running I get 1) high positive short term fuel trims and high (and erratic) long term fuel trims and 2) appear to have some misfires that look like they go away after complete warm up. Graph shows 6 misfires that were steadily going down. (see picture)

Also, the fuel trims are higher during idle and come down at higher RPM. So...

1) I have changed vacuum hoses and can't find any, even during this "warm up" period.
2) Changed fuel filter and run half a dozen or so tank fulls of injector cleaner.

Hypothesis:

With the misfires, could it possibly be from some oil on the plugs and then the oil gets burned off after 15-20 mins? I have read over filling oil can cause misfiring. Not that I specifically recall overfilling but it could be possible. Again the coils are only 18 months old and replaced by Lincoln dealership. Would cleaning and checking gap on plugs be a prudent step?

Any other specific tests? I have never had any misfire codes.

My other hypothesis is a slight exhaust leak. I have a video that shows some slight soot on exhaust manifold gasket.

So, any thoughts? How do misfires cause lean codes?

Thanks again,

Roger

misfires.png
 
Thanks again to Joe for pointing me, and countless others, to misfires. I finally figured out how to check for misfires using my iPhone app diagnostic tools. And before I get yelled at: 04 V8 with all the bells and whistles, 217k miles. All plastics changed out and new coils in mid 2016. Been getting P0171 and P0174 and occasional P2195 and P2197 codes.

It appears that for the first 15-20 mins of the car running I get 1) high positive short term fuel trims and high (and erratic) long term fuel trims and 2) appear to have some misfires that look like they go away after complete warm up. Graph shows 6 misfires that were steadily going down. (see picture)

Also, the fuel trims are higher during idle and come down at higher RPM. So...

1) I have changed vacuum hoses and can't find any, even during this "warm up" period.
2) Changed fuel filter and run half a dozen or so tank fulls of injector cleaner.

Hypothesis:

With the misfires, could it possibly be from some oil on the plugs and then the oil gets burned off after 15-20 mins? I have read over filling oil can cause misfiring. Not that I specifically recall overfilling but it could be possible. Again the coils are only 18 months old and replaced by Lincoln dealership. Would cleaning and checking gap on plugs be a prudent step?

Any other specific tests? I have never had any misfire codes.

My other hypothesis is a slight exhaust leak. I have a video that shows some slight soot on exhaust manifold gasket.

So, any thoughts? How do misfires cause lean codes?

Thanks again,

Roger

View attachment 828568765
I have an 03 LS V8 currently in the shop for similar issues. Found the the throttle body gasket was leaking (using carb cleaner). Lean codes still ongoing. Having the intake gasket replaced today. I will follow up with the outcome.
 
I have an 03 LS V8 currently in the shop for similar issues. Found the the throttle body gasket was leaking (using carb cleaner). Lean codes still ongoing. Having the intake gasket replaced today. I will follow up with the outcome.
Thanks, I have used carb cleaner, brake cleaner, and a propane bottle all around the throttle body and intake manifold with no changes.

Mine only has problems during the morning or first start up period of the day, particularly if I just drive a short distance, turn off the car, then restart it. If I hop on the freeway, things are ok.
 
Have you tried the propane or cleaner under the same circumstances as when you have the most misfires? ("first start up period of the day")

I'll throw out the guess of leaks at the internal gaskets between the plastic and metal parts of the intake manifold.

BTW, the misfire guess came from the symptoms of lean mixture plus gasoline smell. A misfire puts raw gasoline and too much oxygen in the exhaust. The lean/rich mixture determination is made based on the amount of oxygen exhausted from the cylinder, not the amount of fuel.
 
Have you tried the propane or cleaner under the same circumstances as when you have the most misfires? ("first start up period of the day")

I'll throw out the guess of leaks at the internal gaskets between the plastic and metal parts of the intake manifold.

BTW, the misfire guess came from the symptoms of lean mixture plus gasoline smell. A misfire puts raw gasoline and too much oxygen in the exhaust. The lean/rich mixture determination is made based on the amount of oxygen exhausted from the cylinder, not the amount of fuel.
Thanks Joe, I have checked propane there and haven't had any tell tale signs of a leak. And, if I remember correctly, the plastic to metal manifold connections are NOT fixable, right? It is just where the metal part of the manifold meets the motor.

No gas smell today...

What is most baffling and frustrating is that it comes and goes.
 
... It is just where the metal part of the manifold meets the motor...

No, it's where the plastic part of the manifold meets the metal part of the manifold. Those metal blocks with the fuel injectors on each side are part of the intake manifold, not the engine.

The metal part of manifold meets the engine (heads). There's a metal gasket there on each side.

There's some debate on which gaskets fit the internal connections in the manifold between the plastic and the metal. I can't say if those are the right ones are not. Anyway, it may not be this at all.
 
No, it's where the plastic part of the manifold meets the metal part of the manifold. Those metal blocks with the fuel injectors on each side are part of the intake manifold, not the engine.

The metal part of manifold meets the engine (heads). There's a metal gasket there on each side.

There's some debate on which gaskets fit the internal connections in the manifold between the plastic and the metal. I can't say if those are the right ones are not. Anyway, it may not be this at all.
Thanks, yes, that is what I understood but didn't articulate it very well. At this point, I am not sure where to go next. I don't really want to just rip apart the intake manifold and change all the gaskets or do the same with the exhaust manifold and have the issue not resolved.

What other tests or diagnostic tools are there to help me out? I suppose I could take it to the dealership but by the time I got it there the car would be hot enough to operate perfectly.

One other issue that is also still unresolved is that O-32 EGR Monitor Bank 2, 82-Manufacturer specific. I have a positive 0.077 reading and it says it should be between -4.753 and -4.737. I have not checked for a leak in the EGR hose fitting at the exhaust manifold. Maybe there is a leak there that "self seals" when hot????
 
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I'm with you there. I'd do more testing/experimenting before I tore into either of those as well. Unfortunately, I'm out of suggestions at the moment.
 
I'm with you there. I'd do more testing/experimenting before I tore into either of those as well. Unfortunately, I'm out of suggestions at the moment.

thanks, check my "edit" of my last post....

here it is...

One other issue that is also still unresolved is that O-32 EGR Monitor Bank 2, 82-Manufacturer specific. I have a positive 0.077 reading and it says it should be between -4.753 and -4.737. I have not checked for a leak in the EGR hose fitting at the exhaust manifold. Maybe there is a leak there that "self seals" when hot????
 
...One other issue that is also still unresolved is that O-32 EGR Monitor Bank 2, 82-Manufacturer specific. I have a positive 0.077 reading and it says it should be between -4.753 and -4.737. I have not checked for a leak in the EGR hose fitting at the exhaust manifold. Maybe there is a leak there that "self seals" when hot????

There is one parameter that is always red flagged as out of bounds on both of my LSes, and this has been the case since both were new. I assume it is something the test software doesn't know about the LS, rather than an actual problem. I'll try to remember to check this weekend to see if it is indeed that EGR value.
 
156B6F58-4362-4693-A709-2A836E73A0B1.png
There is one parameter that is always red flagged as out of bounds on both of my LSes, and this has been the case since both were new. I assume it is something the test software doesn't know about the LS, rather than an actual problem. I'll try to remember to check this weekend to see if it is indeed that EGR value.
Thanks, here is a picture of what one of my OBD2 apps tells me. I am gonna crawl underneath and see if the EGR/exhaust connection is loose.
 
Crawled underneath and discovered there really isn’t a efficient way to check if the EGR hose/tube is secure. But, I did take this picture from the just past the alternator. There appears to be some soot right where the exhaust manifold attaches (between those lame arrows). Might this be a strong indication of an exhaust leak?

A56C0943-63D8-4283-8D27-BAA7F4118499.jpeg
 
Is that soot, or is that accumulated oil grime (such as is on the wiring harness right there)?
 
Did you get a chance to check which parameter is out of spec on your LS? And, are there any specific readings that my OBD2 app could help with finding the culprit? For example, there are a lot of "Airflow" PIDs that are available: Mass Air Flow, Intake Manifold Absolute pressure... and others: fuel rail pressure, fuel rail pressure relative to manifold vacuum, etc.

However, there doesn't seem to be one labeled, "Here's your problem, ya moron!"

Today, on a 30 mile drive to Santa Barbara, a P2195 and P2197 code came up "pending" . After the return trip home, no codes pending. So, the codes come up then go away depending on how long the car is driven.
 

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