5.9 Magnum very sluggish

PNW 1500 · Feb 19, 2017

So just last night my wife and I were out driving and I started to notice that the truck was acting very sluggish. This morning I had to go do some running around and the truck seemed worse than last night. It is extremely sluggish, when it downshifts like it wants to take off it will not go over 2500 RPM and wont shift up unless I let off the gas pedal. By the time I made it home it was even worse and the acceleration was almost non existent. I was reading on some of the other forums that my cat could be clogged or possibly a bad vac line but I checked all my vac lines and all are hooked up and not slit or rotted. Trans fluid and oil is all at proper level and just fueled up yesterday morning. Does anyone have any idea what this could be. I am extremely new to Dodge so Im not familiar with some of the acronyms and parts that are common issues. Any and all help is greatly appreciated and welcomed. This is my daily driver and I really need it to be operational ASAP and with a little amount of money spent as possible.

Truck is a 1998 extended cab with just under 190K miles. Everything is completely stock on the truck.

jbmobbs · Feb 19, 2017

Pull your first o2 sensor out and drive it. If it runs better then it's a clogged cat

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PNW 1500 · Feb 19, 2017

jbmobbs said:
Pull your first o2 sensor out and drive it. If it runs better then it's a clogged cat

Thanks ill give that a shot

PNW 1500 · Feb 19, 2017

That seems to have worked. But just in case if I replace my cat tomorrow when shop opens and that doesnt seem to cure it completely what else should I check into? Should I replace my O2 sensor while im at it? Its still fairly clean which I was fairly amazed at.

dodge dude94 · Feb 19, 2017

Fix your plenum, replace the O2, and the cat.

Fixed.

PNW 1500 · Feb 19, 2017

dodge dude94 said:
Fix your plenum, replace the O2, and the cat.

Fixed.

What do you mean by fix the plenum? And what's intaled?

Yeret · Feb 19, 2017

You're cat's toast. Are you using oil? If so, I'd bet money that your plenum gasket is also toast and is probably what plugged your cat to begin with. Read this for everything that you need to know about the intake manifold plenum...

http://www.ramforum.com/f61/plenum_gasket_what_where_what_should_i_do_about_*info*-37635/

PNW 1500 · Feb 19, 2017

Yeret said:
You're cat's toast. Are you using oil? If so, I'd bet money that your plenum gasket is also toast and is probably what plugged your cat to begin with. Read this for everything that you need to know about the intake manifold plenum...

http://www.ramforum.com/f61/plenum_gasket_what_where_what_should_i_do_about_*info*-37635/

No I have not used any oil. Just did oil change couple months ago after I bought the truck. I'm only 2nd owner of truck and the guy I bought it from said he had all the gaskets replaced that were in need. He was extremely meticulous with this truck.

dapepper9 · Feb 20, 2017

Start with the cat and the 02 (NTK or Mopar) and go from there. It sounds like the previous owner MAY have dealt with the plenum issue but only time will tell. Monitor oil level and at next oil change do a visual inspection of the cylinder 8 spark plug

PNW 1500 · Feb 20, 2017

dapepper9 said:
Start with the cat and the 02 (NTK or Mopar) and go from there. It sounds like the previous owner MAY have dealt with the plenum issue but only time will tell. Monitor oil level and at next oil change do a visual inspection of the cylinder 8 spark plug

Thanks for the heads up. I have an apt for a new cat tomorrow so hopefully that will help. As for the O2 sensor, the one I removed to do the initial test looked fairly clean, but if I replace it does it unplug up above the transmission? I followed the wires up and it feels as though there is a plug up there but cant seem to see it.

PNW 1500 · Feb 21, 2017

Got cat switched, truck runs great now. Even on the lift my exhaust guy said it's amazing how clean the underside and engine of truck was. At further inspection the element in the cat had broke loose and blown back and was blocking the outlet. Thanks to everyones input and advice. I may still check into the plenum gasket for peace of mind.

Gr8bawana · Feb 22, 2017

Glad to hear problem fixed. :favorites13:

5.9 Magnum very sluggish

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