anyone gurus know the 3.1L V6?
March 31st, 2010, 3:48 PM
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anyone gurus know the 3.1L V6?
Hi,
I was hoping some pro out there knows the early 3.1L engines like the back of your hand! - this is the one that was late 80's, and pre 1995 (before they want to a MAF sensor for OBDII, etc)
I just got my 1993 lumina euro back from my mechanic. He rebuilt the top end of the engine for me, (blown HG) - I even got new remaned heads too, figured, just in case the old one was warped, I wouldn't have to pay the labor 2x, and I got all new gaskets everywhere, the engine is sealed and tight.
anyways, to make a long story short, the Car drives perfect, when you have your foot on the gas going down the hwy - runs like a new car.
When you take your foot off the gas, it will not coast like normal - it only falls to like 45mph, but then does eventually go down to curb idle, where it then runs rough. Never stalls though.
he checked vacuum everywhere, and it's not leaking anywhere....
it throws a SES light, and the code indicated low vacuum at the map - he tried like 5 map Sensors, all good...
I read somewhere that this could really be the fuel pressure regulator, since there is a vacuum line on it, and if that diaphram is shot, it would cause everything here that I am describing, (I think) makes sense to me, but I don't want to guess anymore with it.
makes sense, but the problem is that it's not a simple repair, since the Plenum has to come back off, etc - I'd try it myself, but there are so many vacuum lines that I don't want to brake any of them, and I know it's kind of a bear to get them all tucked under, etc...
here are my questions:
1) how can I confirm it is the fuel pressure regulator without pulling the plenum off and changing it? - would the fuel pressure at the rail be any different at idle than at 3K rpms lets say?
2) anything else this could be? - I can swap an engine coolant temp sensor fairly easy myself, since I think it's right near the T-Stat housing on the intake. Was the only other thing I can think of. I know the temp is correct, as to the gauge, but the engine may not.
TPS seems to work, and the IAC was replaced, and made no difference...
I have like a grand into the car now, and I really can't guess anymore - I need to know for sure what the problem is.
Thanks to all that reply
I was hoping some pro out there knows the early 3.1L engines like the back of your hand! - this is the one that was late 80's, and pre 1995 (before they want to a MAF sensor for OBDII, etc)
I just got my 1993 lumina euro back from my mechanic. He rebuilt the top end of the engine for me, (blown HG) - I even got new remaned heads too, figured, just in case the old one was warped, I wouldn't have to pay the labor 2x, and I got all new gaskets everywhere, the engine is sealed and tight.
anyways, to make a long story short, the Car drives perfect, when you have your foot on the gas going down the hwy - runs like a new car.
When you take your foot off the gas, it will not coast like normal - it only falls to like 45mph, but then does eventually go down to curb idle, where it then runs rough. Never stalls though.
he checked vacuum everywhere, and it's not leaking anywhere....
it throws a SES light, and the code indicated low vacuum at the map - he tried like 5 map Sensors, all good...
I read somewhere that this could really be the fuel pressure regulator, since there is a vacuum line on it, and if that diaphram is shot, it would cause everything here that I am describing, (I think) makes sense to me, but I don't want to guess anymore with it.
makes sense, but the problem is that it's not a simple repair, since the Plenum has to come back off, etc - I'd try it myself, but there are so many vacuum lines that I don't want to brake any of them, and I know it's kind of a bear to get them all tucked under, etc...
here are my questions:
1) how can I confirm it is the fuel pressure regulator without pulling the plenum off and changing it? - would the fuel pressure at the rail be any different at idle than at 3K rpms lets say?
2) anything else this could be? - I can swap an engine coolant temp sensor fairly easy myself, since I think it's right near the T-Stat housing on the intake. Was the only other thing I can think of. I know the temp is correct, as to the gauge, but the engine may not.
TPS seems to work, and the IAC was replaced, and made no difference...
I have like a grand into the car now, and I really can't guess anymore - I need to know for sure what the problem is.
Thanks to all that reply
April 1st, 2010, 9:24 AM
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how much should there be there at idle? - I would assume it's specific to this engine. Also, how does one check to see if the fuel pressure regulator is working correctly? Where does the vacuum line off of that connect to? - I would think that could also be checked for vacuum as well? or does the fuel pressure change depending on demand?
so, at idle, the engine requires a lot less fuel than cruising down the hwy... correct? so, if the fuel pressure reg was not working right, it would be showing the same higher pressure all the time at the rail, correct? - I can connect a tester to the valve there on the rail, but wondering if that will give me a clue...
Thanks
so, at idle, the engine requires a lot less fuel than cruising down the hwy... correct? so, if the fuel pressure reg was not working right, it would be showing the same higher pressure all the time at the rail, correct? - I can connect a tester to the valve there on the rail, but wondering if that will give me a clue...
Thanks
April 1st, 2010, 8:53 PM
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18-21" of vac at the map sensor and the same at the regulator. To test the regulator you need to connect a fuel pressure tester to the test port (if it has one). Start the engine, read the fuel pressure then remove the vac line from the regulator while it is running the fuel pressure should increase.
April 2nd, 2010, 10:46 AM
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yup, it has the port for testing - valve - it's just like a tire valve, and if you depress the stem, it will squirt gas everywhere, etc... it was a lifesaver to find my fuel pump problem... very easy, KOEO, and no pressure, no way the car will start, etc...
where does the Fuel pressure Regulators vacuum line connect to? - I can't get to it without pulling the plenum off the top of the engine, and I'd rather somehow rule it out myself, or find that it's the problem, without having to spend the labor to take off the plenum...
So, I'd need to know what it's supposed to be at idle, vs at like 3000RPM... Im assuming if it's the problem, the reading will be higher than it should be at idle, when vacuum is supposed to lower it, correct?
40 PSI at idle? or lower or what?
Thanks
where does the Fuel pressure Regulators vacuum line connect to? - I can't get to it without pulling the plenum off the top of the engine, and I'd rather somehow rule it out myself, or find that it's the problem, without having to spend the labor to take off the plenum...
So, I'd need to know what it's supposed to be at idle, vs at like 3000RPM... Im assuming if it's the problem, the reading will be higher than it should be at idle, when vacuum is supposed to lower it, correct?
40 PSI at idle? or lower or what?
Thanks
April 4th, 2010, 7:32 AM
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So, one more time on this question - The easiest thing for me to do at the moment, is to get a fuel pressure gauge, and hook it up to the fuel rail (via the fitting that is capped there)
What I want to know is how much pressure should I have at A) idle, and B) at 2500RPM?
if the reading is the same, does that mean the fuel pressure regulator is the problem?
if it is different, what kind of difference should I be seeing? 10PSI? 20?
Also, is this a good way to rule it out, or to point to it as the problem?
I just don't want to get soaked at an "engine specialized" type place, which is what I think I need now, but at least it would be good to know something before I hand it over
Thanks to anyone that can help me with this first step...
What I want to know is how much pressure should I have at A) idle, and B) at 2500RPM?
if the reading is the same, does that mean the fuel pressure regulator is the problem?
if it is different, what kind of difference should I be seeing? 10PSI? 20?
Also, is this a good way to rule it out, or to point to it as the problem?
I just don't want to get soaked at an "engine specialized" type place, which is what I think I need now, but at least it would be good to know something before I hand it over
Thanks to anyone that can help me with this first step...
April 9th, 2010, 11:33 PM
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Update
Ok,
so, if any of you have been following this, I finally decided to bring it into the dealership, where I figured they would know how to fix this....
the guy that did the repair didn't many things back together correctly on top, like one of the plenum gaskets, etc...
so, $350 later, the car now has a new EGR valve, new fuel pressure regulator, right gaskets, etc...
the high acelleration problem I guess is fixed now, but they still can't get it to idle correctly - the service manager called me at 5pm today, and said that they need more time to diag the problem, but can't seem to find it yet...
my fear is that I'm going to spend another $160 on diag fees and they still will not find the problem...
he didn't tell me if it's throwing any codes - but I would assume that if it was, he'd let me know that - it was before....
So, now we are only dealing with a rough idle.... do these older 3.1s maybe have to re-learn idle? I read somewhere that it takes like 10 key on and offs or something to get the ECM to set the idle correctly?
is this just idle speed that it's learning? or is it also rich/lean, etc... maybe it's running rich, and will lean out?
anything anyone can think of? - Thanks
so, if any of you have been following this, I finally decided to bring it into the dealership, where I figured they would know how to fix this....
the guy that did the repair didn't many things back together correctly on top, like one of the plenum gaskets, etc...
so, $350 later, the car now has a new EGR valve, new fuel pressure regulator, right gaskets, etc...
the high acelleration problem I guess is fixed now, but they still can't get it to idle correctly - the service manager called me at 5pm today, and said that they need more time to diag the problem, but can't seem to find it yet...
my fear is that I'm going to spend another $160 on diag fees and they still will not find the problem...
he didn't tell me if it's throwing any codes - but I would assume that if it was, he'd let me know that - it was before....
So, now we are only dealing with a rough idle.... do these older 3.1s maybe have to re-learn idle? I read somewhere that it takes like 10 key on and offs or something to get the ECM to set the idle correctly?
is this just idle speed that it's learning? or is it also rich/lean, etc... maybe it's running rich, and will lean out?
anything anyone can think of? - Thanks
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April 14th, 2010, 11:01 AM
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Finally Found the Problem...
Hi All,
Ok, it only took 3 mechanics and $2000 to find the problem...
The previous mechanic never bothered to match the heads up with the original ones, and the casting numbers were not the same... I was never told that this was VERY important thing to know, and of course, the place I bought them from blames me for ordering the wrong ones, and blames the mechanic for not checking them the ports were very close, but not exact match at the lower intake, so they were never going to seal correctly.
so, I will have to decide of I have a case against the previous mechanic for his negligence... I will have all the paperwork from the dealer to prove it in court, but I don't want to waste my time, if I don't have a strong enough case.
I'm not a mechanic - I would think, that if I hired someone to do a job like this, the first thing they would have checked was if the heads were the same, since he was the only one to have them both in his hands at the same time....
Any opinions welcome....
Ok, it only took 3 mechanics and $2000 to find the problem...
The previous mechanic never bothered to match the heads up with the original ones, and the casting numbers were not the same... I was never told that this was VERY important thing to know, and of course, the place I bought them from blames me for ordering the wrong ones, and blames the mechanic for not checking them the ports were very close, but not exact match at the lower intake, so they were never going to seal correctly.
so, I will have to decide of I have a case against the previous mechanic for his negligence... I will have all the paperwork from the dealer to prove it in court, but I don't want to waste my time, if I don't have a strong enough case.
I'm not a mechanic - I would think, that if I hired someone to do a job like this, the first thing they would have checked was if the heads were the same, since he was the only one to have them both in his hands at the same time....
Any opinions welcome....
April 14th, 2010, 8:33 PM
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It all depends on how different they looked. They make have been only slightly different and may not have been noticeable. We (mechanics) rely on the correct parts to be provided by the parts store. The parts store must be given the correct info. Some parts must be ordered using the Vin # (especially heads if there is more than one option). If the shop provided the heads you would a rock solid case. Since you provided the heads you are kind of at fault also. It would be a hard case to win and could go either way. You got to decide is it worth the time and money to pursue it, or just chalk it up as an expensive life lesson.
April 15th, 2010, 8:54 PM
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Yeah, but he claimed that the reason it was leaking was a warped lower intake manifold, so he made me pay him again to tear it back down, and buy a bone yard one, which he said he couldn't give me because they sent my old one for scrap...
The guy at the dealership says that if the intake warped from it overheating, the block would have melted... meaning that never happens...
The problem is that he charged me 2x to tear down the engine, and didn't even look the first time to see if the ports lined up correctly - you can clearly see this according to the dealership service manager... he did know that it was leaking down there, so he found that, but I shouldn't have to pay for his shotty work on my car...
he was supposed to fix an exhaust leak, guess what? still leaks... he was supposed to bleed the brakes after he replaced the new calipers - guess what? petal goes to the floor, cause he never did it correctly....
so, I still do not have a case? - I'll eat the fact that I have to pay 2x for heads, since I gave him the wrong ones lets say, but I shouldn't have to pay for the 2nd tear down, since that was 2x he missed the original problem on the car.
I am going to try the easy way first, and see if he will settle for 1/2 of what I paid him... once I show him in writing everything that is being re-done that he should have done right in the first place...
The guy at the dealership says that if the intake warped from it overheating, the block would have melted... meaning that never happens...
The problem is that he charged me 2x to tear down the engine, and didn't even look the first time to see if the ports lined up correctly - you can clearly see this according to the dealership service manager... he did know that it was leaking down there, so he found that, but I shouldn't have to pay for his shotty work on my car...
he was supposed to fix an exhaust leak, guess what? still leaks... he was supposed to bleed the brakes after he replaced the new calipers - guess what? petal goes to the floor, cause he never did it correctly....
so, I still do not have a case? - I'll eat the fact that I have to pay 2x for heads, since I gave him the wrong ones lets say, but I shouldn't have to pay for the 2nd tear down, since that was 2x he missed the original problem on the car.
I am going to try the easy way first, and see if he will settle for 1/2 of what I paid him... once I show him in writing everything that is being re-done that he should have done right in the first place...