unplug the MAP sensor and take it for a spin

 

Gonna have to try that and post results.

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Just out of curiosity, am I running it with the map sensor unplugged just to see if the condition is unchanged (meaning a map sensor failure) or to see if the turbo or fueling reacts differently (which I am assuming it would have to without the input of the map sensor to the computer). Or is this to make the computer relearn/refresh after plugging the map sensor back in after clearing the inevitable CEL? Or will you answer "yes" to all?

 

most of the time a cel light is set when your map sensor is bad

 

Ok, sorry it took so long. Things have been hectic around here. But I have finally done as you suggested and unplugged the MAP sensor and drove it for about a mile. As expected, the CEL lit up, and the truck was in super limp mode. Got to the end of the road, a shut it down, re-plugged the MAP sensor...

Holy freakin cow man! This truck has retard strength again! I cleared all the codes after writing them down and drove to town. AMAZING difference. I'm guessing that the truck had to re-learn the sensor, or had to be slapped in the face and told to pay attention to it.

Boost isn't 100% as it was before this ordeal started, so I'll have to dig into that some more but it's way better than it was. EGT's have dropped, and that's a good thing. I'll drive it around some more, and see if it begins to degrade back into wimp mode.

 

You might want to clean your IAT and MAP sensors. Also, early 05's had plastic tank intercoolers on them and they are known to crack and leak so I would also check that unless you have an 05.5 with the all aluminum intercooler.

 

I've recently pulled my map sensor (which is also my iat, I think) and it looks like brand new.

I do have the plastic tanks on my intercooler (built 07 of 2004). I am going to try to find time to pull the intercooler and test it for leaks. I guess I could do the same with it as I do with radiators, cut an inner tube, clamp it to the input/output flanges, and submerge it in a tub of water and pressurize it. Is there a better way? Anything in particular that I need to watch for while pulling it out of the truck? Tips/tricks?

The ducting for the intercooler is an upgrade kit, complete with T-bar style clamps. I tried testing for leaks on the truck, just not real confident that it was a successful test.

 

For reference, the IAT (intake air temp) sensor is located on the cold air intake tube where your air filter is. The MAP sensor is on the intake manifold plane up near the rail pressure sensor. I have included a picture of it circled in red.

You can pressurize the intercooler in the truck if you like. Just plug one end and then clamp a 3" PVC nipple to the other end with a schrader valve in it and put about 10-15 PSI in it. Then, get a spray bottle with some Dawn or the like and water mixture and spray away. If you want to take it out, which would be a better and more thorough test, then the only trick is when you take the condensing unit loose all you have to do is rotate is about 180 degrees while moving it up out of the way towards the passenger side of the truck and over the front of the cowel. This way you don't have to discharge the A/C system and it leaves everything in tact. Just zipt tie it up out of the way. There are rubber bushings on the two upper keepers that you have to make sure and get lined up properly upon reinstallation but it is very straight forward. Good luck.

 

It's been a couple days now, and still running strong. I does sound like I'm dumping boost though, and my numbers are still low. Gonna try capping the plumbing at the intake horn and see if I can pressurize the intercooler and ducting, try to narrow this down some more. Hopefully it will be a simple leak and not the wastegate messing up.

 

Finally figured it out, not happy about what I found, but glad the problem was isolated.

Blew the end cap right off.

Now to try to see if I can make it go back together

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Freakin' perfect. I'm missing about a 3" section of the rubber gasket that seals the tank. I have to assume it went into the engine at some point, so I can only hope that it got consumed and isn't still in there somewhere. Getting that tank off was a pita all by it's self, but with a wood chisel and a 8mm wrench (as a pry bar) I was able to ease all the little tabs back to release the tank. Maybe I got lucky and the piece of gasket was blown OUT of the intercooler.

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Well, I pulled a Pheonix project fix on it (richard dean anderson would be proud).

I pulled the plastic end cap off, carefully pried all the little tabs out until the cap would set back on without obstruction, and proceeded to silicone the crapola out of it. I honestly didn't have any faith in this temporary fix, but after some cure time and the reinstall, I took it for a test drive. I made it to the end of the road, and pulling out from the stop sign I got up to about 11psi and POW! I figured it was catastrophic failure of the patch, but it turned out to be the boot blown off the intake horn. So I re-seated it, ran over all the clamps again to ensure they were tight, and down the road again I topped at 22psi (not wanting to push it too hard and press my luck). That's good enough for me for now, I just hope it holds until I can find a replacement IC. Gotta source an all-metal tank. The plastic end cap design is crap.

Long story short, my PO299 = busted intercooler = boost dump.

Anybody got a good IC laying around for cheap?

 

It sounds like the map sensor. If u unpluged it and pluged it back in and it started working better i would probley start there. There pretty cheep and easy to replace