niceguypmp3

on my '06 uplander with the 3.5L and 223k for about a year now then when accelerating it's low on power. I'll describe what it does. When accelerating, it starts to lose power at around 2500-2800 rpms. it wont go any higher than about 3000 rpms and it just falls on it's face. no codes showing. If you manually pull it down into 1st gear and slowly accelerate then it will go 4000+ without falling on it's face but if you get into it then it faulters. when pulling a hill then it doesn't pull as hard in OD as it used to and so it downshifts to 3rd. Less power at that 2500-2800 that 3rd gear at 55mph has. if it needs to downshift to 2nd then when it tries to do the downshift, it just loses all power and instead of the rpms going up, then actually go down like you just let off the throttle. if you let off the gas or shut off cruise and it goes back to 3rd or OD and then will start to slowly accelerate again. When it tries the downshift to 2nd and then you stop it, then you get a momentary odor in the vents that is almost gaslike or exhaust like. the odor only comes during that time. when it's pulling a hill in 3rd gear then if you slightly let off the gas then it will start to pull a little better. Everything was telling me lack of fuel, so i assumed either fuel pump or the in tank fuel filter. I took it to the dealer and they said that it has great fuel pressure at all rpm's but they couldnt test drive it to see if it drops during a hard pull. So in their opinion it's not the pump or filter. they checked exhaust flow thinking maybe the cat and that checked out good. They are going to do some more checks, but after i explained in further detail what it does, they think it may be something with the transmission. I know uplanders are notorious for trans problems but it's not slipping that i can tell. Unless it starts slipping slightly and it lowers engine power to help stop the slipping but i get no reduced engine power message. Anyone have any idea what it may be or where to check? Any help would be greatly appreciated!

niceguypmp3

The dealer was stumped as to the problem until their oldest mechanic with about 45 years experience looked at it and he figured out that the problem was due to a huge vacuum leak. upon further inspection, he discovered that the intake air boot between the mass air flow sensor and the throttle body was split about 3/4 the way around so it was sucking alot more air than the sensor was detecting which was making it have an extremely lean run. they ordered a new boot and in the mean time they put silicone on the crack and i am driving it. it's better than it was but not 100% yet so the silicone must not be completely sealing it. i'll find out if the problem is solved when i put the new boot on it.

Papa Bear

Thanks for the update ! Looking forward to hearing how the new boot affected the fault.

niceguypmp3

ok, another update. I got the new boot put on tonight and no change whatsoever. so i figured maybe the mass air flow sensor needed cleaned. so i took it off and noticed the air filter looked strange. took out the air filter and it weighed like 5 pounds. that thing was completely 100% plugged with dust. So i banged it on the ground until no more fell out of it and then put it back in and now it runs perfectly fine! that filter is only a year or so old. These uplanders must have a poor design for the intake for the air filter box and it must suck dust really bad. Now i'll have to check the air filter every few months. good thing it isn't too hard to check.