Hey everyone. I'm new to the forum and am sending out my first call for help. I picked up a 2001 RAM 1500 4x4 with the 5.9L earlier this year and lately, it's developed a real annoying hesitation. After starting the truck and driving for a minute or so, I get a severe hesitation that's so bad, if you try to accelerate, there’s practically no throttle response and the truck will backfire. If you floor it, either nothing happens or the truck revs to the red line but doesn’t seem to
go anywhere. After a minute or so of this, if you keep standing on the accelerator, the problem will go away and the truck will run fine. It sort of works it's way through the issue and clears itself up. If you stop and shut the truck off, it comes back once you start driving again.
The truck has a new throttle position sensor and a new Idle Air Control motor. It also has brand new plugs, wires, cap, & rotor. I have no check engine light and can't seem to figure this out. The way the problem shows up and then goes away every time, makes me think it's a sensor of some sort. It's definitely most predominant when the truck is warmed up.

Any help would be greatly appreciated.

 

More than likely you have a plugged CAT. Get a hammer and bang on it and see if it rattles. You could also disconnect your front O2 sensor, leave the wires plugged in and leave the sensor hanging. Now take the truck for a drive and see how it feels. If it drives better, then that's your proof right there, your CAT is bad.

 

I had a similar problem,turned out it was a bad O2 sensor, Speed Control Sensor, and my Shift Linkage was loose and wasnt fully grabing.

 

^^+1 on the cat being your culprit. The o2 sensor could be going as well due to excessive heat build up from the blocked cat.

 

Thank you to everyone who's responded. I took out the O2 sensor as suggested and took the truck for a drive. It seemed to run better so I took it over to the local exhaust shop and had them cut out the cat. The guy said it wasn't the worst he'd ever seen but it was definitely starting to get plugged so I had them install a new Magnaflow cat and the truck ran pretty good coming home.

Went out this morning to go somewhere, started her up, and wouldn't you know it, about a mile into the drive as usual, it starts again. Step on the gas and the engine just about dies, backfires through the TB, no power at all. Stomp on the accelerator a few times....nothing. Try once more, the RPM's go up to about 5K but the truck doesn't take off so I back off and floor it one more time.....and that does the trick. From this point I can drive it all day without a problem UNTIL, I shut the damn thing off. Then the process starts again. And I never get a CEL when this happens.

I'm stumped. I picked up the truck in January with a bad transmission. Had that removed and completely rebuilt with all new parts, electronics, converter, etc. Replaced the IAC in March when that died. I've done a complete tuneup with plugs, wires, cap, and rotor. Pulled the TB and completely cleaned that. Checked inside the manifold and didn't see any puddles of oil, just a light varnishing so I reinstalled the TB with a new gasket and a new throttle position sensor.

Could it be the O2 sensor? MAP sensor? Crank Position Sensor?
Could it be compression related? I'm not getting any cylinder misfire codes...

The thing runs great other than this issue.

 

After doing all this work did you disconnect the battery to clear all codes?
If the cat was bad it is possible that your front O2 may be bad or acting up. It may be worth a try to replace it. Afterward, be sure to disconnect the battery.

 

hey larry, read your post and i am having the exact same pooblem execpt mine seems to do it more when you first get going ,but happens when warm too. i have had it to 2 garages and no one knows what is wrong. have changed out just about every sensor including front o2 sensor and checked fuel pressure. if u figure it out could you please post the fix, as the mechanics don't have a clue unless they can read it off the codes.



Thanks,
Al

 

Hey Ram15002ndGen...thanks for the help! I took your advice, as well as others on this forum, and so far, the hesitation is gone.

Al......here's what I did to solve it:

1) Replaced the cat. When we took it out, the exhaust shop said it was definitely starting to plug up. He estimated it was about 30% plugged, maybe a little more, so put in a Magnaflow cat.

2) I replaced both the before cat and after cat O2 sensors. I did both since the truck has almost 124K on it and figured while I was under there, it's no more effort to do both. One word of caution here...take the old O2 sensor out and bring it with you to the parts store so you can match up the connector. My truck is a 2001 and I bought the ones listed in the parts catalog but when I got home with them, they had the wrong connectors. Turns out that even though I have a 2001 model year truck, the sensors are model year 2002 and have square connectors instead of round connectors.

3) Finally, after installing the new O2 sensors, I disconnected the battery to clear any codes.

So far, it's running good.

Can't thank everyone enough for some excellent advice. You guys are the best!

-- Larry