Won't rev over 4500 rpm

[MDA]

I swear I have a vacuum leak. I was looking around to try and find any hose issues. Didn't see any. Started her up. Rev and it only goes to 4500. I know that it's throwing a P0420. Would that actually cause limp mode?

 

[VPRPWRD]

clogged catalytic converter

 

[hawk02]

I think that with no load on the motor/free rev it limits it at 4500rpm, how is it driving, if you get on it will it go over 4500????

 

[MDA]

Forgot to mention I have no cats.

Havent tried it while driving yet.

 

[VPRPWRD]

Do you have the o2 cheater harnesses on? P0420 is catalytic converter efficiency code, could also be a bad o2 sensor giving the PCM a false reading.

 

[MDA]

Just cleared the 0420. Still doesn't rev over 4500. I'll try it under load in a little while.

 

[VPRPWRD]

Let us know what happens when you drive it.

 

[hawk02]

I think I may have it mixed up with my old 05 Hemi, that had a 4500 limiter in park and "N", not sure if Dodge did it with these trucks, but I wouldn't want to free rev it over that anyway......

 

[MDA]

Do you have the o2 cheater harnesses on? P0420 is catalytic converter efficiency code, could also be a bad o2 sensor giving the PCM a false reading.

As far as I know, I do not have that. Truck was bought with these MODs.

 

[VPRPWRD]

Have you had it for a while or did you just recently purchase it?

 

[MDA]

Just drove her and went past 4500. Guess it is limited when in park.

I've had it for about a month.

 

[VPRPWRD]

Well that's good to know, did the p0420 come back?

 

[MDA]

Yes it did.

 

[VENOMOUS1 RACING]

Bad O2 sensor! Does it have a tuner? sCT handheld? Does it have O2 simulators on rear O2s?

 

[hawk02]

Nice to know, same as my old Dodge Hemi truck. I finally knew the right info!!! LOL

 

[VPRPWRD]

You definitely need to get o2 sims on the rear o2 sensors, but at least it sounds like your revving "problem" isn't really a problem at all.

 

[MDA]

Thanks for all the replies everyone.

About the o2 problem... I do not have a sct. I need to get one. If I get the sct will I still need the sims?

 

[VENOMOUS1 RACING]

Thanks for all the replies everyone.

About the o2 problem... I do not have a sct. I need to get one. If I get the sct will I still need the sims?

No but you'll need to have good O2s there, they are just tuned out. Could very well be a front O2 acting up which fuel the engine correctly.