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Simultaneous P0401 and P0171

R

robinsone

New member
So I have 200k on my N/A GP. New wires, coils, fairly new plugs, MAF, MAP, EGR, throttle body cleaned, O2 sensor, air filter.

Its thrown the P0401 and I took it into a shop they said the EGR ports were clear enough. I had disassembled part of the EGR tubes and cleaned them out best I could. Not sure if I've cracked one of the EGR pipes at all?

Could it be a bad CAT? or a clogged one.

I've also been pretty good at using lucas fuel and seafoam on a regular basis and kinda want to swap out my injectors because they're due.

It doesn't run rough or idle poorly, nor am I getting a bad smell on start-up, or anything else that would normally tip me off to the problem.

Let me know what you guys think and what I could tackle next, thanks.
 


I'd try smoking the engine to find the P0171 code, likely a small leak somewhere.

Maybe the P0401 is because of the leak or the EGR tubes and both won't be from a cat converter, both these codes are on parts that work before the converter.
 
The P0401 is a code most should read up on. I've seen guys spend tons trying to find an EGR problem. Go to GearChatter.com and look up an F body tech DTC on this code (it's a GM FSM essentially). It'll point out in the diagnostic aids that flow is measured by the map sensor. And if you aren't getting any other EGR codes for lack of movement etc.. usually it's not an EGR problem.

If your map isn't reading airflow properly you could be fuelling incorrectly as well, hence the P0171
 
So it looked like there was a crack in the tube on top of the upper intake manifold. Not sure what its called, the plumbing which runs back into the intake prior to the throttle body. I replaced so we'll see what happens. Is there a way to install an air/oil separator or catch can here? Not sure if it would help whatsoever.

What I also found was the map sensor pretty well soaked in oil. I had replaced the PCV sometime ago and it was bone dry more or less. This time when I picked up the map sensor there was a visible amount of oil, a small puddle and everything was soaked with oil. I cleaned everything with intake cleaner, minus the map sensor. Not sure if you can spray anything in the actual sensor.

This is what was most likely contributing to the EGR code I was seeing I'm guessing. It looks like I need to take off the upper intake manifold and de-grease it so to speak. I will assume that the excess oil in the map sensor might be do to a build up in the pockets of the manifold/plenum area. I know when I swapped out the lower intake manifold gaskets there was quite a bit of oil here.

Is there any good way of reducing the amount of oil entering the intake. I realize the PCV is somewhat internal and there is no external plumbing, but would placing one on that top piping of the upper intake manifold make any sort of impact on catching any excess oil at all. Please let me know, thanks.
 
pull the pcv valve out and see if its caked up with oil.

map should not be wet with oil. unless it leak into it from a valve cover or some retarded thing, the line to it sucks air, not pushing it into the map.

dis regard, i forgot to check the section this was in first.......dumb ass i am.
 
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Not sure what piping you are talking about. Unless you mean the one inside the UIM. That's there to ensure the oil is dropped consistently. It's totally normal for oil to be there, however your pcv may not be functioning properly. One o ring below it.. and another on the cap that holds the pcv in place.

As mentioned, your map is likely bad. I'd spray it.. worse case is it's already bad and you need a new one.
 


This is the tube or piping I'm talking about, pic attached. I switched out the PCV with the complete kit, new o-rings, spring, cap etc along with a new MAP sensor to boot. So I'm not sure what could be causing the oil accumulation. I have been running a considerable number of highway miles recently.

If I interrupted the tube/piping shown with an air oil separator would that have any affect in reducing the amount of oil introduced into the intake?
 

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Ahh the vacuum tube.

No putting something in there wouldn't help with the oil. The oil may be caused from high rpm, pushing/beating on it.
 
So after clearing out the MAP and PCV valve of excess oil the code went away. Driving to and from Chicago from Indianapolis with no problems and no code. I assume I have excess oil consumption due to the large number of highway miles I've put on the car recently. I run either Mobil 1 or Valvoline full synthetic and I lose about a quart per 4k I believe.

I've replaced the oil pan gasket, valve cover gaskets, lower intake manifold gaskets, and front main seal so I know I'm not losing oil there, in theory. Would swapping out the valve stem seals perhaps decrease the oil consumption. I know there is a TSB for the '05-'08 models, but not sure about an '04.

Would love to know what you all thought about swapping those out especially with the mileage, 201k, I have now.

Let me know, thanks.
 
dont change the valve seals unless you see smoke out the tail pipes after it sits all day or over night, aka super cold start.

no smoke dont touch em
 
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