FAQ: 3.8L V6 Ignition Surging
All of a sudden your car has just started to act funny. It just seems like it's out of power, or the car just shudders/skips/sputters violently. This is a typical 3.8 V6 problem.
The solution is either electrical or physical. You will have to go through a few things before you can determine whichever it may be.
Since your ignition system uses several components in sync, the cause could be one or more things. --
On the CFI 3.8 V6, there's a TFI chip underneath the distributor cap that likes to blow out suddenly; this can also cause the car not to start. On EFI cars, the same chip is located on the outer distributor housing but since it's away from the heat underneath the cap, it's a bit more reliable.
It could also be a bad throttle position sensor, which causes all sorts of strange things to happen to your car. It could also be a bad idle air controller, bad spark plugs, spark plug wires, ignition coil, or even a bad EEC computer.
1984-85 V6 cars are especially susceptible to faulty EEC-IV computers from the factory; they usually go between 40,000-50,000 miles. This is a trial-and-error kind of problem, unless you have a computer code reader. Fortunately most of the components are not very expensive and can be found rather easily.
If you've determined that the cause is not electrical, you just may have yourself a bad timing chain. The 3.8 timing chain will stretch over time the 3.8L seems particularly susceptible. The stretched chain will allow the valve opening and closing, and your piston and firing order, to become out of sync with each other. Eventually this will severely affect performance and can cause the camshaft to snap.
As a general rule, a new timing gear set and chain should be installed every 75,000 miles on a 3.8 V6.
This problem usually will not show up on an EEC tester. As common as this problem is though, it may just be the ticket to new life in your engine.