My Buddy has a 98 1500 4x4, Im posting this for him here, as you guys have been very helpfull to me in the past and hoping you can help him out too!

As title says, no matter how hard he stomps on it, wont go faster than 40-45km/h , also rpms cap out at about 3k. Engine also sounds like a total bag of ****.

Just started happening randomly. Any ideas?

He says CEL light is on, I am going over after work to read his codes with my reader, but right now dont know what they are yet.

I know his Plenum is F-ed, could that be it?

He has new plugs, wires, cap, rotor, and Catalytic.

 

How new are the plugs, wires and cat? Is the air filter clean? What circumstances lead up to the current situation? Go back and figure out what he has done to the truck recently and go from there.

 

Plugs, wires, air filter, and cat all new within 2 months.

He says he drove it to work fine Yesterday, parked all day, after work, got in and it was running like a bag of crap.

I checked his Plenum by looking down the intake with a flashlight when we did his plugs and there is some oil in there, No big pool, but its definatly not clean, I assume it is blown. Hes planning an Engine swap next year so hes been putting that off.

 

OK, next question, when you say sounds like a "total bag of s***", what exactly do you mean? Knocking? Pinging? Exhaust sounds bad?

 

However new the cat, it's suspect when those symptoms appear. And especially after you write "I know his Plenum is F-ed".

Some small bit of oil on the plenum belly pan is perfectly normal, thanks to the PCV valve. And especially if your buddy is one of those who has never replaced the valve. So now the question is: Is the plenum pan gasket truly hosed? Or is that merely a supposition?

A failing crank position sensor can also limit RPM and cause missing at higher RPM.

 

+1 onnall the points above....but pull the upsteam O2 sensor and see what it does. If it rund better, then the cat is already jacked.

 

Well you guys were right again, We pulled his front O2 and it ran much better, was able to get up to highway speeds no problem. Must be the Cat.

Thanks for the tips guys.

 

Wouldn't a cat that is 2 months or less old taking a crap be a definitive symptom of a severely blown plenum?