I put a new transmission in my truck and all was well beforehand. When i took it out and testdrove it it was fine as well or atleast i think so as i hadnt driven it for a while. Well then i seafoamed it b/c there was a bit of carbon buildup in the intake. It looked like a damn brushfire going down the road it was so bad. Shortly after that the power went to crap. It would barely accelerate without really mashing on it. So i decide to change the spark plugs and all but the #6 and #8 cylinder were caked with carbon. It started up and idled better but now it is worse than ever with power. It will barely go 65 down the road without having to give it so much throttle it downshifts into second. On top of that, i got a whopping 152 miles before my gas light came on with the 26 gal tank. thats only about 6 mPG when it was getting 18 MPG before this.

Could this be a plenum gasket, clogged cat converter (it is rattling bad and the exhuast got a lot quieter), or a computer problem? It is running so rich that it looks like a damn diesel smoking black when i step on it and it burns your eyes. Its obviously way too rich.

 

My first thought is the cat has gotten clogged. If it stopped rattling, started running rich, exhaust sound got quieter, spark plugs full of carbon buildup, getting poor gas mileage, and you've lost power since running the Seafoam through it, I would highly suspect the cat has become clogged. I don't recall hearing of anyone clogging the cat by running Seafoam through their system, but I have always wondered if it was possible. My first place to look at closer would be the cat and the pre-cat O2 sensor. The sensor may have been coated / damaged from the Seafoam breaking loose all of the carbon buildup.

 

well the truth is i tried to hollow the cat due to it rattling since i dont have emissions and they are very expensive. It was rattling b/c there was a few pieces that i could not break up that were still in there. Well after the seafoam i took it on some spirited runs and then it stopped rattling. I am guessing that at high RPM the piece might have finally got stuck in there just right. We will see if this is the problem when i put the true duels with straight pipes on in the next couple weeks.

 

While taking it for a run, those loose pieces may have become lodged in the pipe opening, thus blocking exhaust gases.

 

well now i have an excuse for true duel straight pipes. But i think it also has something to do with the plenum gasket. It has too much buildup in the throttle body and it burns oil in the high rpms. We will see when i recover from the money i spent on the trans. Its my secondary vehichle so w/e ya know.

 

Looking down the TB is not the best way to check the plenum! Block off the breather tube at the valve cover, block off the PCV valve hose at the intake (hose and intake )and see if you have pressure or vaccum at the dipstick tube. Pressure is good , vaccum is not.

 

Zman, i will try this in just a little bit.

Update to the problem:

Decided to park on some concrete and put a load on it with a brake toque of sorts. The whole time it was under a load it was poaring black smoke out of the tailpipe and did not even have the power to break the tires loose. It was missing a bit, but that could be due to it loading up so much, or it could be it missing that is causing it to load up. I cannot make sense of the problem. There is no missfire light or anything. i would think if it were running that rich that the computer would lean it out with readings from the oxygen sensor. Could the oxygen sensor be the problem? i do have a code 21, but i am 99% sure that it is from the after cat 02sensor considering the cat is gutless.

Well off to try zman's trick... i will update afterwards

 

alright so I tried zman's way and the thing was sucking massive vacuum. If this is a true sign of a bad plenum I will be replacing it right away. I just need some confirmation before I spend the time and money. I need this thing running its getting sold. I was at the dodge dealer and was looking at a new ctd and I think I am going to buy one!

 

Even if it wasn't bad, its not a bad idea to replace it with the APS or Hughes kit anyway. That way it should never go out. Thinking about doing it myself here soon, after a bit more $$$ finds its way into my pockets.

Even if you decide to sell it, will a buyer notice the problems you've been talking about? Most likely! So the repair is a necessity anyway.

 

Does not compute. Vacuum leaks mean unmetered airflow, which means lean running condition. Check your fuel trims. Sounds to me likea MAPsensor issue.