Hi, I'm new here and I have kind of a wierd problem. My 2001 durango 4.7 makes a not too loud popping noise at between 4300 or 4600, followed by a big loss in power - enough that the engine won't get past 4700 rpm even in 1st gear. Engine makes real good power and torque below 4000, and is smooth and quiet otherwise.

My friend is telling me its bad cats, but the engine also sounds so much different, I just don't think thats it. I can tell many cylinders aren't firing right. I'm thinking something more like bad valve springs or sticky valves or adjusters. But there is 167k on it. I tried searching for similar situations, but didn't find much.

Also, once you lose the power, it stays lost until the rpms drop to about 3500 or so. So what was good power at 4000 is now gone unless I let it slow back down. Now that I type this I realize there is a better chance it could be a cat on one side. Although the truck did recently just pass a california smog test.

 

that is the torque curve of the 4.7, it falls off just under 5k RPM, this is pretty standard and does not indicate a problem. I would like to ask you why you are reving it up that high, its not necessary w/ a v8 that makes good torque in the lower end of the RPM range, it is more efficient to keep the revs down, and does not have a major effect on performance to do so (even when im driving hard i dont get above 5k)

 

Yes I made sure to look at that same graph 2 days ago, and yes I know what a low end torque cam feels like we have a 2006 nissan armada, tons of torque and nothing after 4500. Pulls our bass boat up the grapevine like its not even there.

That said, your right, 90% of the time under 4000 will be fine. But as low as 4300 rpm the engine will pop and starts running on about 3 cylinders, trust me I know its not the end of the power band... Maybe I should make a video, to help explain better.

I have a scanner and there are no codes coming up, I did have an evap leak, but I found it (old cracked and disconnected hose) and fixed it already.

Any help is much appreciated.

 

Here is a video I took this morning

 

ok that is definitely not normal, you have an OBDII logger, what is the pre-cat oxygen sensor doing during this? do you have a solid cam and/or crank sensor issue? no MAF sensor on these trucks so that isnt the issue.

 

Thanks for getting back to me. It always starts right up and I've never seen any kind of sensor codes come up in the month or so that I've owned it.

I don't know if its a computer problem or valve train problem but I think I can smell exhaust from the intake after this happens. Or at least I get some exhaust smell in the cab, even though the truck is moving forward the whole time. I thought maybe the map sensor would show something.

I can try looking at the 02 sensors next. Maybe try a computer reset too. But I got some stripped wheel studs I discovered while I was tightening up the rear brakes that I gotta replace. This truck was previously owned by the state of CA general services so theres my problem lol...

 

This plug is from the #7 cylinder. I noticed half of it is all black, should that mean anything?

 

 

Well I still have good power under 4k so I'm not too worried. I probably need a compression check and a leak down test. I noticed a brand new water pump on there so that kinda scares me a little bit. I just think its maybe weak springs and or maybe the valve guides are bad. I have 49 psi on the fuel rail and it holds well when I stab the throttle.

...........

I had no bumpstops, and my shocks were the stock chrysler ones at 160k miles. I could fully collapse the shocks in 1 second flat with 1 hand lol. For $39 these gabriel ultra shocks seem pretty dang nice. No more bouncing on metal to metal suspension for me. It took only 5 minutes a side to change out the bumpstops and shocks, super easy.

Probably get some all terrain tires tomarrow, I'm thinking yokohama geolander ats, the sidewall tread looks pretty sweet, and I had them on my work truck before.

 

Looks like you run fuel cleaners, and a lot of it too. It is not good to do that, and from the look of it you need to replace the plugs as well. Go get you a new set of Champion Copper plugs, yes the cheap ones and gap to .040 and install.