'96 B2500 rough idle, could it be the MAP?

Hello,
I have a '96 B2500 with 5.9. About 2 years ago we had a new/rebuilt (jasper) engine put in it because it had a rod knocking. Not too long after that we noticed the idle was a little rough. Over the year or
two it has gotten to the point of being real rough. Idles smooth while cold, as it warms it gets to a point where it increases 300 RPMs or more then drops off.
The manual says check vacuum first. I did this today and found a busted line from the throttle body to some kind of solenoid. I replaced that line, the PCV, and air filter, the condition is still there.
After some research and study I think the MAP or Intake Air sensors could cause my problem. Before outlaying that kind of money to see if a replacement would work, is there anything else I should be concerned with?
Thank you, Fred
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In response to fawilson 's post. I thought everyone should know:

cant recall and i dont have a 96 service manual here. but does it have an EGR? might wanna check it if it does.
--
Chris

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Great question, but no, there is not an egr.
wrote:

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In response to fawilson 's post. I thought everyone should know:

so much for my shot in the dark off the hip guess. LOL
any codes?
--
Chris

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Once again, another great question, but Nope, no codes.
I did unplug the MAP while it was running, and boy did that screw things up. I suspect that the MAP might be fine so now thinking about the Intake Air Control valve.
wrote:

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Are you sure? It left the factory with one, located behind the injector for the #8 cylinder.
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John,
There is not one there. I even looked at the sticker on the hood for the emissions stuff, there is not one listed there either.
Fred

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So here is what I've done so far. I took out the Intake air valve and found that it was all crusty and carboned up, also it had a rattle to it. I got a new one and put it on there and it seem to help for a little bit, however, the idle is much lower and much more calm. So I think I am getting closer even though it still is pulsating.
It could be my imagination but it seem to have a little better takeoff power too.
My wife is out now getting a MAP sensor and an intake air temperature sensor. I will put both of those in and see. It will be my luck that it is the throttle position sensor.
Any comments?
Thanks, Fred

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You may not like it but you asked.. <BG> I really hate guessing on these symptoms any more. Unless it's something really common a wrong guess can get expensive. Would this not be a good time to have someone/mechanic/dealer put a scanner on it and actually diagnose the problem before throwing more parts at it??? It may be cheaper in the long run.
No offense intended of course.....
Denny
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Denny,
I guess I am done throwing money at it today. I have replaced the Idle air valve, the intake air temp sensor and the map sensor. Although it has surely made a difference, the rushing is still there. I did take the time to clean the throat area of the of the throttle body really well, nice and shiny. I also ensured all the rubber vacuum lines are replaced. I have tested the voltage to and from the TPS and it is good. So unless it is a fuel filter, fuel pump or a crack somewhere I am lost.
The thing that gets me is that now the thing has way more torque than it has ever had since I have had it and after the engine change. Something I discovered because now it has get up and go, it hits the Rev limiter before it shifts out of 3rd gear. Going to have to have that looked at.
So now it is to get ball joints, shocks, springs, and the air conditioner serviced (got a hole somewhere). Also, I am going to have to find a steering column coupler.
Fred
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