How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Doug in North Carolina Your Own Question
Doug in North Carolina
Doug in North Carolina, ASE Certified Technician
Category: Dodge
Satisfied Customers: 302
Experience:  ASE Master Mechanic, 12 Years Experience Specializing in HVAC, Electrical and Driveability Problems.
Type Your Dodge Question Here...
Doug in North Carolina is online now
A new question is answered every 9 seconds

I have a 96 Dodge Intrepid 3.5L 140K. It has a rough idle

This answer was rated:

I have a '96 Dodge Intrepid 3.5L 140K. It has a rough idle and when cruising at 60 mph it runs the same way, almost like it's starving for fuel. I took it to a shop and they said the scanner only found a fluctuating fuel injector. I replace the injector and it acts the same way. I use a bottle of Iso-Heet (fuel-line antifreeze, water remover & injector cleaner) with every fill up (I live in Alaska). I replaced the spark plugs 2 months ago and the fuel filter 1.5 yrs ago. Spark plugs all look good and uniform. I used new gaskets when I replaced injectors.

Good day. My name is XXXXX XXXXX I'd like to assist you with the rough idle. Do you have any fault codes causing the check engine light to come on? This would help isolate the diagnostics to a certain area of the powertrain system.


Next would be what type of plugs did you put back in and what was the spark plug gap set to?


What's the history on your plug wires, do they still have a date printed on them and if so what is it?


Do you smell any raw gas from the engine bay?



Customer: replied 7 years ago.

I don't have a have code reader. Do you have one you would suggest?


Spark plugs: Autolite Platnum, I didn't adjust the gap

The issue started about a week ago. The plugs have been in for almost two months. Are there O-rings some that can be replaced in the valve covers for the spark plugs? There was a little oil on a few of the plug when I inspected them, but the endes of the plugs all looked good and uniform.


Plug wires: Belden Premium High Temp. 7mm GD, I have not changed the wires, I have owned the car for two years.


No raw gas




If you've got oil in the spark plug tube wells then that's going to be a big area of concern. The oil can soak through the plug wire boot and cause spark to short to the metal tube rather than go through the spark plug and jump the gap.


Next would be the spark plugs. Champion works best for your vehicle and quite honestly, I've not seen a case where autolites worked good any any car for the last 10 years. Many times they will keep the car running for a short period of time but give it a couple of months and they begin to act up. Also, you don't need to fork over the money platinum plugs for this application. The simple copper plus plugs work just fine. Most people think Champion plugs are junk and I do see them as the plug of choice for lawnmowers. But... they really do work wonders in a chrysler product.


You wires would also be suspect now since they've been exposed to the oil. When you do the plugs I'd recomend doing the wires as well just to be on the safe side. Keep in mind if you've got oil in those spark plug tubes then unless you fix that then you will just ruin your new plugs.


I asked about the raw gas smell because the 3.5L had problems with the fuel rail cracking. If you don't smell any fuel then I would not attribute the idle issue to the fuel rail.


The last two things that come to mind are the intake manifold bolts and the EGR valve. The intake plenum is the large piece that sits over both valve covers. It bolts to the intake manifold between the valve covers. The bolts that hold it down to each cylinder head sometimes broke which would cause the engine to pull air in. This can be checked by spraying a carb cleaner in a number of places around where the intake manifold meets the heads. You'll be listening for a sucking noise or a change in the idle (either it flares up or starts to stumble).


The EGR valve is designed to route exhaust gases back in to the intake stream in order to cool down combustion temperatures. Sounds silly but the hot exhaust gases are actually inert and when introduced it really does cool down the temperature a little. Regardless, this device sometimes would stick partially open causing a rough idle or a surge as your at a sustained speed. If you have a vacuum gague then you'd be able to see a slight flutter at idle which could indicate the EGR valve is partially opened when it should be completely closed. If it's stuck open even a little then the computer doesn't know it and does not make the necessary adjustments to calculate the fuel corrections.


I'd recomend starting with Champion plugs, new wires and fixing your oil leaks. j


Doug in North Carolina and 3 other Dodge Specialists are ready to help you
Customer: replied 7 years ago.
Do you have any ideas to fix the oil leaks? Or would you suggest removing the valve covers and fix something that way?

Removing the valve cover would be the best way to fix this. It allows you to clean the gasket mating surfaces thoroughly of any old gasket material but also oil that gets caked there. If I'm not mistaken the 3.5L has large threaded caps that hold the valve cover to the spark plug tubes. These caps come off and the tube seal is under it and can be serviced without removal of the valve cover itself. I'm away from most of my technical information but could provide better answers for you either tomorrow night when I'm back home or Monday morning.


I do not suggest any kind of oil stop leak. Stop leaks are bad for clogging up passages that are needed for coolant and oil flow so stear clear of that.


Are you able to wait until later for additional answers or did you need it by tonight or tomorrow morning?


Customer: replied 7 years ago.

I should be able to get it from here. I appreciate the help.



Ok, Thank you for using Just Answer and good luck with your work.