I am having a major problem with my 2001 Ram with a 5.2. I have seen this issue in a few posts but I have not seen a fix for it yet. Heres what the symptoms are
The engine will start up fine and idle fine. After about five minutes of idleing the engne will start to stumble and miss. It gets progressivly worse and almost stalls. If I hit the gas it revs right up with out any problems. Then it will go back to stumbling again. When driving, it hapens when the truck goes into overdrive and the RPMs lower down to 1500 RPM. Then the engine will cut out, back fire, spit and sputter. If I floor it it will take right off and go. It only seems to happen at low rpms when driving.
Heres what I have done so far....
Cap,rotor, wires, plugs. I have OHMED out the coil, it was fine, i checked the Pick Up coil or Cam Postion Sensor and it was fine. I checked the fuel pressure at the rail and it was fine, it was about 50 psi, although it did seem to flutter when the engine was stumbling / Missing but it never dropped below 40 psi.
I am stumped. From some of the other posts I have seen I am thinking it maybe the fuel pump. Although it really seems like it is somthing with the Ignition / Spark. The exhuast seems to be flowing fine so I wouldnt think that it is the CAT.
Any Suggestions you have will be greatly appreciated.

 

Have you checked/replaced the front O2 sensor? There was someone on the forum that had a similar problem recently and it turned out to be the O2 or IAC. Can't remember which.

 

Have you ever tested a IAC valve ? It does throw a code for the O2 sensor but I assumed that it was just comng up from the extra gas in the exhuast from the stumbling /Missing. The IAC valve does sound logical, I will check it out. I will check the O2 sensor also.

 

+1 o2 sensor

 

has been happening to me randomly. try throwing some octane booster in the truck, or since gas is so cheap run some 91 octane through it. I havent had the stumbling/surging since i have put octane booster and switched to 91 octane last month.

 

its free to try- clean your iac valve. also clean the area around the iac valve. its only two torque screws. how many miles are on your truck? have you checked your plenum gasket? also you may want to clean your throttle body- it only cost the price of the throttle body gasket. so its close to free.

 

I checked the IAC valve and it seemed to be frozen in the extended postion. I was able push in and out but it was very tight. My manual said to unplug the sensor with the engine running and listen for an idle change, I did not notice any idle change. The manual also said that with the sensor off the throttle body, but still plugged in, turn the key on and the shaft should retract. The valve did not move at all. The valve was pretty dirty.
Long story short, I replaced the valve. It was 41.99 at autozone. Right away i noticed a difference in the intial idle speed. I let the truck idle for awhile and it did not start to stumble or miss. I took the truck for a ride and for the first mile or so it did stumble, miss, and back fire. I know usually you have to drive at 35 mph or for a certain time for the valve to program itself. It still stumbled, which pissed me off so I got on it a little. The more I drove it the better it got. I drove it up and down the road for about a total of five miles , making sure to stop and start again to see if it would stumble, and it did not.
For now the problem seems to be gone, but it is still early. I let the truck idle for about five minutes when I pulled in the garage ( yes the door was open!!) it did not stumble or miss. So far I am happy, but like I said it is still early yet. I will keep you posted.
Oh yeah befoe I forget, the truck has 105,000 miles on it. I have not changed the plentum gasket yet or cleaned the throttle body. I think I will clean the throttle body this weekend. I did look down the throttle body and it looked fairly clean.

 

the last time mine was stalling at stop signs and idling crazy it was the TPS. also about $40.

 

I had a 97 ram with the 5.2 it a very severe miss i did everything i could think of then less then a month later it quit completly IT WAS THE FEUL PUMP!!! AND I WAS 40 MILES AWAY FROM HOME if I were you I would replace it before it gets you stranded like mine did. after that it run fine for about a year then started missing bad again and it was because of a lifter sticking. If the check engine light is on put it on a computer and it should teel you which cylinders are missing.the feul pump will cost you 2 to 3 hundred.I sold my 97 and now have a 01 quad cab 4x4 360(5.9L).

 

The IAC valve was not the problem. The stumble / Miss is still there. I talked with a technician friend of mine and he siad change the coil and wires. The wires have a lifetime warranty and the coil will cost about 30 bucks. If that doesn't fix it then I will change the fuel pump. Thanks for all of your responses, I will pst my results.