3.8L V6 Surging
Page Revised: 10 May 2019
So you're driving around minding your own business, when suddenly the car just seems like it's out of power, or maybe the car just shudders and skips and sputters violently. You have just become the victim of a typical 3.8L V6 problem. The solution is either electrical or physical, and you have to wade through a few things first before you can determine whichever it is.
Since your ignition system uses several components in sync, the cause could be one or more things. On the 3.8L V6, there's a TFI (thick film ignition) module on the distributor that likes to blow out suddenly; this can also cause the car not to start. It could also be a bad TPS (throttle position sensor), which causes all sorts of strange things to happen to your car. A bad or sticking IAC (idle air controller) motor is also very common on these cars; you might consider checking and/or replacing it. Other culprits could be bad spark plugs, spark plug wires, ignition coil, EGR valve, MAP sensor, or even a bad EEC computer. The 1984-85 V6 cars are especially susceptible to faulty EEC-IV computers from the factory. This is a trial-and-error kind of problem, unless you have a computer code reader, but 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, then you just may have a bad timing chain. The 3.8 timing chain will stretch over time (as do all timing chains) but for some reason, this engine 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 3.8L V6. And this problem usually will not show up on an EEC tester. If you are experiencing this problem, we'd recommend getting a second opinion from a qualified mechanic. As common as this problem is though, it just could be the ticket to new life in your engine.