I've been having an occasional problem with a "sputtering" engine on my 2002 Ram 1500 (5.9 liter).

Here's the scenario: ......The motor starts & idles just fine, and also accelerates from an initial dead stop just fine. However, a frequent problem has been occurring when I let off the gas in order coast through a yield or come to a stop. Then, when I gently accelerate after just letting off the gas, it tends to sputter & hesitate, but runs great at full power after I get above 25mph or so. This problem only occurs at slower speeds. If I pull the truck over while it is still sputtering, then turn off the engine & re-start it, the engine runs fine again. I am not getting any "Check Engine Light" or error codes (DTC's) activated.

Here's what I've tried so far: ......Installed new spark plugs & wires (re-routing them to permit adequate isolation), cleaned the cap & rotor contacts, removed & thoroughly cleaned the entire Throttle Body, installed new Idle Air Control Valve (IAC) & Throttle Position TP Sensor (TPS), verified proper vacuum w/ no leaks detected, verified no leak in the plenum, the PCV is good, & both of the upstream Oxy Sensors were just replaced. I have also temporarily connected a fuel pressure gauge, and the monitored pressure remains steady at 49psi (with NO noticeable fluctuation). I've disconnected the battery (& drained all residual power) several times in order to reset the PCM.

I was wondering if this is due to a glitch in the Powertrain Control Module (PCM), and if I need to get the computer re-programmed in order to resolve the problem. "AutomotiveComputerExchange.com" can provide a fresh re-programmed PCM for around $280, but I was wondering if this is a necessary step to take.

Any advice-help would be appreciated. Thanks!

(2002 Dodge Ram 1500 ST Sport Quad-Cab 4x4, 5.9 liter, automatic, 79000 miles)

 

Could be the fuel pump.

 

If it is the fuel pump, then why does the fuel pressure gauge indicate steady pressure at 49psi? If the pump was failing, wouldn't there be a pressure drop at the same time I am encountering the sputter?

 

Sorry, I glossed over that. Was the gauge there during idle or while driving? Just thinking out loud.

 

i doubt that its the pcm.

you mentioned cleaning dist cap and rotor... i would replace them.

gentle acceleration problems can be related to leaky vacuum. as a simple test, i'd disconnect and plug the vac ports at the manifold, just to see if it fixes it.

other random thoughts. coil, cam pos sensor in bottom of dist, crank pos sensor, water in gas.

i'd run a big dose of gas treatment/fuel injection cleaner through it. might not help, but its cheap and won't hurt anything.

has it always done this, or is it a recent problem?
if recent, did it start after any kind of service, or event, or anything ?

if nothing else develops, you might take it to someone with a scanner for diagnosis. i'd think about 1 hr or less at $60-80 ought to cover it. it might save you from throwing parts at it.

 

Sputtering could also be cause by a faulty camshaft sensor, which is in the base of the distributor. Clean and inspect it as well before replacing anything. It could be something as simple as a broken wire.

 

Thanks for the input. The Camshaft Position Sensor was inspected & verified to be in good condition. Coil is good. Fuel has been purchased from various locations for some time now, so water shouldn't be an issue. Thoroughly tested for vacuum leaks, none detected.

The problem started to occur at a random, with no modifications or recent service being a factor. It has been occurring more frequently, but sometimes there is no indication of any problem. It runs great for awhile, then occurs again.

Each time I reset the PCM (by disconnecting battery & dumping all residual power), the engine "re-learns", runs great, then I get the sputtering & hesitation again. It does this regardles of engine temperature as well.

???? ........I'm at a loss for some fresh ideas now.

 

My truck use to cut out every time I hit a bump. It ended up being the coil harness that was giving a faulty connection. Just a thought. Good luck

 

Like others said, I would replace the distributor cap and rotor. Easy, pretty cheap, and won't hurt anything.

If that doesn't solve it... how did your reroute the wires? Did you route them as per the TSB from Dodge? I doubt its that, since its not a constant thing, but just another easy to do thing that won't hurt. What plugs did you install?

Take off the air cleaner assembly and look down into the intake manifold with a flashlight. Any oil in there? These engines are notorious for the broken plenum gasket, 99% of them are affected by that it seems. I thought mine was barely broken until I had it taken off and replaced with a modified intake... it was SERIOUSLY broken, probably a half pint of oil in the manifold itself. I just couldn't see it until after it was off.

I'd try running a slightly higher octane of gas. If you run 87 now, try two or so fill-ups with 89/91/equivalent. If that gets rid of your problem, then its possible oil from the broken plenum is getting into your gas and causing a lean mixture. Also, along the same lines, see if you can't test (or have someone test) your injectors. Thats probably more likely to cause a hesitation then a lean mixture, actually. Usually a lean mixture will cause pinging at WOT long before you have hesitation/misfire.

 

Thanks for the input. The inside of the plenum is dry & clean. Also, I tried running some 91 octane for awhile .....didn't make any difference. Thanks anyway.