I have a 2004 Pacifica, 3.5 engine with 108,000 miles on it. The car has an interment bucking/hesitating; like the gas petal is not working and then surges after pumping it several times. This happens regardless of temperature. This can happen while cruising at 50 miles an hour or just pulling out of the driveway. Sometimes while idling, or at a stop light, the engine will start to run very rough; not a miss but a fluctuation in idle speed. The idle will drops so low it sometimes stalls. I took it to a Chrysler dealership and had them check it out. They found a bad O2 sensor which they replaced. It did not fix the problem. I replaced all the spark plugs and wires, cleaned the throttle body while the upper manifold was off, and checked the silicone gasket. I ran some injector cleaner through the infectors and replaced the Throttle Position Sensor. I use only OEM parts. I pulled the Idle Air Control Motor, cleaned it, and it moved when the ignition was turned on. I also cleaned the manifold Turning Valve but I don’t know if it works. I am stuck? What else should I check?

 

That engine interminent hesitation/buckling is cause by a bad EGR valve. I had a similar problem. I had it replaced by a mechanic for $160.00 including the EGR valve. The vehicle has no more hesitation and its running about 24.6 mpg

 

Thanks for the reply. I will change the EGR valve because “sometimes” while idling the engine will begin to run very rough. My problems could be caused by multiple problems. I don’t think the EGR valve would cause the engine to act like it has just become disconnected from the accelerator pedal. You can be driving down the road at 30 mph and the engine goes silent and pushing the pedal doesn’t do anything.

 

This just happened to me yesterday for the first time. I'm driving down the road maybe have gone maybe and mile and the gas pedal does nothing and the engine sounds like it wants to stall. Most of the time it doesn't and I just pump the gas pedal for a few minutes and then I'm okay the rest of my trip. Of course til I get back in the car to go to next desitnation and same problem all over again. Just started yesterday. Kinda scary!

 

Do you have a question? EGR valve you are wondering?

 

Hi. I am experiencing the same problem with my 2005 Chrysler Pacifica. It drives fine then out of no where it stalls and there is no power in the gas pedal. I conducted research on 2005 Chrysler Pacificas and there are tons of people out there with the same issues. There are two recalls one for the headlight and one with a fuel pump module-don't know if this is the problem. It is scary driving the car because you don't know when it will do this. My husband would get in the car and it wouldn't do anything. It is currently in the shop now and if I find out what the problem is I will let you know.

 

Oh by the way a Chrysler customer car rep advised us that is what we get for buying a used car when we were inquiring about the recalls.

 

Did u change both oxigen sensors or was it just one at the time?

 

My 2004 Pacifica has a complete loss of throttle when starting out in the morning or once the car has been off for 15-20 minutes. I also have replaced a lot of components and done a lot of work trying to correct this problem, but the fix has alluded me. I have a laptop with an OBD2 connection and Digimoto software. I have an error code 02 sensor 1/1 Heater Circuit. Until I clear this error I don’t think I can move on. My understanding is that before the O2 sensor is above 600 degrees it will not produce the 0-1 volt needed by the PCM to control the fuel. Even if I let the car idle until it reaches operating temperature the car will still act like the throttle is not connected for about 10 seconds while driving. I have no control of accelerating the car until it decides to go and then lurches into acceleration. I can avoid this situation (before it happens) by shifting into neutral and raising the RPM’s of the engine to 2000 and holding it there for 20 seconds. I believe this raises the O2 sensor temperature and corrects the problem because the car drives normally after that. I can’t do this first thing in the morning because the whole exhaust system is cold but if I warm it up first or drive a little ways and then raise the RPM’s the car will work fine. If I’m in slow traffic or idle a long period of time the engine will begin it’s erratic idle and I must raise the RPM’s again or when the light turns green traffic will piles up behind me waiting for the engine to go.
The throttle position sensor (TPS) continues to work sending to the PCM the correct pedal position throughout all my test runs. Once hot the O2 sensor sends a constant varying voltage between .1 and .9. (as read by my software) but before that is at 1.2 volts and stays there. The problem happens when the fuel rails go from open loop to closed loop. My understanding is that if O2 voltage is not supplied to the PCM it will supply it itself. I think it is doing that but for some reason between the hand off from the open loop to the close loop there is a gap in O2 voltage. When this happens the PCM shuts down the fuel infectors. Once the correct voltage is supplied the engine works fine. I do not have the 5 volt heater voltage going to the O2 sensor as reported by the error code (P0031). There is a 4 prong connector connecting the upstream O2 sensor to the PCM. At that plug check the brown wire with a tan strip for 5 volts while the engine is running. The black/light green wire is the ground. My wire is not grounded but I checked it with the car off. Today I will recheck it with the car running to be sure. The manual say check out with heater circuit with the DRBIII, which I don’t have, so my checks are all with a meter. The manuals conclusion is to replace the PCM unit. I know from many other post on the internet just changing the PCM will not guarantee me a fix. I think there are other problems I’m missing. Before I go any farther I must have the O2 heater circuit working and I believe I have a grounding problem. About 2 weeks ago the passenger door started giving an interment “Door Ajar” warning. The interior lights will come on and will drain the battery if the car is shut off. If it happens while driving I have to listen to Ding, Ding, Ding, the whole trip. Several months ago the back hatch started opening up all on its own for a week.
I’ve added an extra body ground but that didn’t help. I will be removing the PCM and cleaning it making sure it is grounded today and check O2 ground. The manual tells me there are 2 grounds, a power ground and sensor ground. It looks like I need to check G101 (lower left side of engine) and G102 (left side on engine).
sseverett

 

That's definitely your EGR valve. I had the same symptoms and I went to the dealership and bought one and changed it myself. Took a hour to replace and drives perfect. I believe the part was around $30. Very easy to do if you have the right tools.