vacum problem please help
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vacum problem please help My LY6 is throwing a P0068 code (Throttle Position Sensor Inconsistent with the Mass Air Flow Sensor) the symptoms are surging at idle after warm and dying.
I read that some of the causes could be a vacum issue. I started looking at my engine and questioning the way i have some ports capped. Could i possibly need to put a line connecting the two places i have capped in this photo? I looked at my 05 silverado and the line coming from the valve cover on it goes to the throttle body.
I read that some of the causes could be a vacum issue. I started looking at my engine and questioning the way i have some ports capped. Could i possibly need to put a line connecting the two places i have capped in this photo? I looked at my 05 silverado and the line coming from the valve cover on it goes to the throttle body.
Last edited by bfrank79; Mar 12, 2012 at 10:02 PM.
I see your running a breather on your oil filler. Are you still running a PCV system ?
One issue could be that the PCV is pulling un-metered air in via the Breather. The PCV system should be pulling in freah are from the intake and post MAF. System shuold be closed if you have a PCV system.
But, a little more details on what you have and what you did.
BC
One issue could be that the PCV is pulling un-metered air in via the Breather. The PCV system should be pulling in freah are from the intake and post MAF. System shuold be closed if you have a PCV system.
But, a little more details on what you have and what you did.
BC
I would recommend connecting everthing back up as stock.. There is some good to a PCV system.. and bad.. But this has been the subject of many threads.. you research and beleive what you want. I do run closed PCV systems on my cars. No beathers. If you go Breathers. you should not run a PCV system in my thinking. Blow by pressure will cause the breathers to oil up and maybe spit out oil.
The good is that most engine do need to have neg pressure, it can help seat the rings and stop blow by... (you see most racing car/engine do run a evacuation system)
Bad.. if you have oil comsumption. It will suck oil into the system, catch can is the answer to help that.
I am sure many will chim in and give you there words.. or flame me.. LOL.. but that is my 2 cents..
Let us know what you try and the results..
BC
The good is that most engine do need to have neg pressure, it can help seat the rings and stop blow by... (you see most racing car/engine do run a evacuation system)
Bad.. if you have oil comsumption. It will suck oil into the system, catch can is the answer to help that.
I am sure many will chim in and give you there words.. or flame me.. LOL.. but that is my 2 cents..
Let us know what you try and the results..
BC
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the breather could. i've never had good luck running breathers like that on modern fords. i'm not sure about gm's....but i'd think that's a place to start.
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I would recommend connecting everthing back up as stock.. There is some good to a PCV system.. and bad.. But this has been the subject of many threads.. you research and beleive what you want. I do run closed PCV systems on my cars. No beathers. If you go Breathers. you should not run a PCV system in my thinking. Blow by pressure will cause the breathers to oil up and maybe spit out oil.
The good is that most engine do need to have neg pressure, it can help seat the rings and stop blow by... (you see most racing car/engine do run a evacuation system)
Bad.. if you have oil comsumption. It will suck oil into the system, catch can is the answer to help that.
I am sure many will chim in and give you there words.. or flame me.. LOL.. but that is my 2 cents..
Let us know what you try and the results..
BC
The good is that most engine do need to have neg pressure, it can help seat the rings and stop blow by... (you see most racing car/engine do run a evacuation system)
Bad.. if you have oil comsumption. It will suck oil into the system, catch can is the answer to help that.
I am sure many will chim in and give you there words.. or flame me.. LOL.. but that is my 2 cents..
Let us know what you try and the results..
BC
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On The Tree
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ok, so i am going to put the regular cap back on and see what happens
but as far as those 2 ports pictured, i cant figure out where they were connected stock, i have searched on here and google for a pic but cant come up with one, i think they should just be connected together but not 100%, and suggestion?
but as far as those 2 ports pictured, i cant figure out where they were connected stock, i have searched on here and google for a pic but cant come up with one, i think they should just be connected together but not 100%, and suggestion?
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Since I've never worked on a Truck Intake. I can't answer what they are... sorry.. maybe a few more pictures of the PCV hose and the ports again and some of the others will chim in.
BC
BC
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ok, so i just looked at my neighbors truck and on it there is a line connecting the valve cover to the air intake between the maf and the throttle body. and the one on the intake mainfold goes to the evap system (which i deleted) how should i connect these? or should i?
You can delete the EVAP.. that shouldn't be a problem. I would put the cap back on the oil filler and connect the tube as you found on your friends truck..being post MAF.. the ECM/PCM will take into account of the air flow. Hopefully that will resolve your issue.. keep us posted. But Check over everything else that might cause a vacumn leak or ??
BC
BC
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ok, so i just looked at my neighbors truck and on it there is a line connecting the valve cover to the air intake between the maf and the throttle body. and the one on the intake mainfold goes to the evap system (which i deleted) how should i connect these? or should i?
unless you've tuned it, i'd reconnect the evap too. this system stores fuel vapors, and purges them into the intake system under heavy throttle. this system is in lieu of simply venting the fuel vapors to the atmosphere. also, unless it's tuned, this system will more than likely pop your CEL.
The one on the valve cover is suppose to be the block vent. If you had connected it to the intake manifold any air getting drawn through the PCV vac line would have been drawn from downstream of the MAF. As it is, the PCV air is being drawn through the breathers. That means it isn't being measured by the MAF resulting in your error code.
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ok so should I
A) connect the port from the valve cover to the port that is capped on the manifold?
B)drill a hole in the air intake tube behind/in front of the maf and run a line from the valve cover to there. and leave the port on the intake capped?
C) Same as B but uncap the port on intake and run it somewhere?
with all of these choices i am putting the oil cap back on inplace of the breather
A) connect the port from the valve cover to the port that is capped on the manifold?
B)drill a hole in the air intake tube behind/in front of the maf and run a line from the valve cover to there. and leave the port on the intake capped?
C) Same as B but uncap the port on intake and run it somewhere?
with all of these choices i am putting the oil cap back on inplace of the breather
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ok so should I
A) connect the port from the valve cover to the port that is capped on the manifold?
B)drill a hole in the air intake tube behind/in front of the maf and run a line from the valve cover to there. and leave the port on the intake capped?
C) Same as B but uncap the port on intake and run it somewhere?
with all of these choices i am putting the oil cap back on inplace of the breather
A) connect the port from the valve cover to the port that is capped on the manifold?
B)drill a hole in the air intake tube behind/in front of the maf and run a line from the valve cover to there. and leave the port on the intake capped?
C) Same as B but uncap the port on intake and run it somewhere?
with all of these choices i am putting the oil cap back on inplace of the breather
just for the heck of it...post exactly what this vehicle is, with engine. if you could, also give me the 8th VIN. i'll see if i can find some vacuum diagrams for ya.
Since I am not familuar with the Truck Intake or what the port is for.
Question, is it behind the Throttle Body.(as one of the pictures shows). ?.. when the engine is running.. is there vacumn ?.. if you uncap it.. and blow air through it. does it exit the front of the Throttle Body freely?... if so. .I would think that it is the fresh air port. and you can connect the valve cover port to it..
Else I would route it to the intake tube just in front of the Throttle Body, but after the MAF.
But like 1ltcap suggest.. You need to look at the FSM for PCV routing of the hose.. but would need information on what year and model the engine came from.
Take a look at this thread.. it is not related to your question, but it is about truck intake. there is are a picture or two that show the valve cover port connected (one with Carbon on the top). And a few show ports. Might help some..
https://ls1tech.com/forums/conversio...k-intakes.html
BC
Question, is it behind the Throttle Body.(as one of the pictures shows). ?.. when the engine is running.. is there vacumn ?.. if you uncap it.. and blow air through it. does it exit the front of the Throttle Body freely?... if so. .I would think that it is the fresh air port. and you can connect the valve cover port to it..
Else I would route it to the intake tube just in front of the Throttle Body, but after the MAF.
But like 1ltcap suggest.. You need to look at the FSM for PCV routing of the hose.. but would need information on what year and model the engine came from.
Take a look at this thread.. it is not related to your question, but it is about truck intake. there is are a picture or two that show the valve cover port connected (one with Carbon on the top). And a few show ports. Might help some..
https://ls1tech.com/forums/conversio...k-intakes.html
BC
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And i appreciate the help guys.
Thread Starter
On The Tree
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"Since I am not familuar with the Truck Intake or what the port is for.
Question, is it behind the Throttle Body.(as one of the pictures shows). ?.. when the engine is running.. is there vacumn ?.. if you uncap it.. and blow air through it. does it exit the front of the Throttle Body freely?... if so. .I would think that it is the fresh air port. and you can connect the valve cover port to it."
I am not positive about this but i do not think that is a frash air port because factory it goes to the little module on the fuel rail for the EVAP system, but i could be wrong.
Question, is it behind the Throttle Body.(as one of the pictures shows). ?.. when the engine is running.. is there vacumn ?.. if you uncap it.. and blow air through it. does it exit the front of the Throttle Body freely?... if so. .I would think that it is the fresh air port. and you can connect the valve cover port to it."
I am not positive about this but i do not think that is a frash air port because factory it goes to the little module on the fuel rail for the EVAP system, but i could be wrong.
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ok, so here is a pic of what i did. I routed the valve cover vent to the intake, post MAF, and put on a regular oil cap. Same problem still exists. It will crank up and idle just fine, put after you drive it for a while and come to a stop, it surges and dies. 
The other picture is of the PCV valve routed to the back of the other valve cover.
The other picture is of the PCV valve routed to the back of the other valve cover.