I have a question that several dealers were not able to resolve! I have a 2003 Town and Country Limited 3.8L and 125K mi. It has a subtle miss when the motor is under a load (say 45 mph in high gear going up a hill). It also idles a little rough. The vehicle has not thrown any codes. With the above miles and everything original, I performed the following. I have installed spark plugs, wires, and coil pack with absolutely not change. After some research, I'm leaning toward cleaning the throttle body. Can you give me your opinion/advice? Thanks so much. Also, I bought the T&C used and the carfax showed it was serviced regularly at dealer. It does burn quart of oil in 2000 miles. I do all my work myself. I enjoy a challenge, but this one has me stumped. Also, if you recommend the throttle body to be cleaned, do you recommend the Mopar cleaner or can I go to Auto Zone for cleaner? Are there any other web sites or forums you recommend for guidance/video etc. I am not familiar with how this forum works. Would you please email to [email protected] Thanks.

Did you use the same Champion spark plugs that originally came in the vehicle. I've seen too many instances where non-Champion plugs break down quickly on Chrysler products. In one instance, a Dodge pickup truck would not start after two weeks. The original Champion plugs were installed and it fired right up and ran like a top. Gap the plugs to spec.

Use any throttle body cleaner, to clean the throttle plate and throttle body--I use Valvoline Throttle Body Cleaner.

Thank you for the quick response. I could not easily find the Champion plugs,so I had it crossed over to NGK. I don't like and usually don't substitute, but with the new plugs, then wire, then coil pack, the symptoms stayed exactly the same; therefore, it seams that I didn't properly identify the problem. I feel certain if I put the old plugs back in or got the exact champion plugs, the problem would still be present. Again, thanks for your response. Do you feel the carbon build up is the next logical step? Any idea on average time to clean the throttle body. I'm not per say a mechanic, but have done several intake gaskets, trany and mtr replacements. I did have a 5.4 expedition and cleaned the throttle body. I remember a special grease required on the throttle body that was a requirement for proper operation. Thanks.

The subtle "miss" may be a slight case of engine knock. This link may help:

https://www.askmehelpdesk.com/cars-t...tml#post324106

See if the problem goes away by using slightly higher octane gas. Ultimately, I suspect you need to install a colder running set of Champion spark plugs--the NGK plugs are likely too hot.

Start using full synthetic SAE 5W-30 engine oil. This will slightly lower the octane requirement and help the engine to run cooler and cleaner. Conventional engine oil evaporates easier (higher NOACK Volatility), which is burned, causing sludge and engine knock problems.

I would try some fuel injector cleaner, I had the same problem in a Jeep and a good quality injector cleaner fixed it!!