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discipled1
02-09-2005, 06:10 AM
troubleshooting: 3.8 v6 surging

For all 3.8 V6 engines

So you're driving around minding your own business, when suddenly the car just goes goofy on you. It just seems like it's out of oomph, or maybe the car just shudders and skips and sputters violently. You have just become the victim of a typical 3.8 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 CFI 3.8 V6, there's a TFI (thick film ignition) 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 TPS (throttle position sensor), which causes all sorts of strange things to happen to your car. It could also be a bad IAC (idle air controller), bad spark plugs, spark plug wires, ignition coil, or even a bad EEC computer. The 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, 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 yourself 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 3.8 V6. And this problem usually will not show up on an EEC tester. If you are experiencing this problem, I'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

The above information form www.coolcats.net/tech/troubleshooting
Cool Cats (http://www.coolcats.net/tech/troubleshooting/surge.html)

David Neibert
02-09-2005, 09:41 AM
That info is specific to the 1983-1986 NA 3.8, not the distrubitorless ignition system we use. The SC timing chain is very durable and has a good tensioner. I've never seen one fail or stretch to the point that it caused a problem with engine performance.

David

scbird1
02-09-2005, 10:29 AM
The tensioner might wear out after 200k but it will still be in perfect time. Try those old gm`s with the nylon mesh gear that falls apart after 80k :eek:
Some of the old electronics can be fun but the EEC will throw you some codes
Most of that stuff is made in japan

J.D.
02-09-2005, 12:39 PM
That info is specific to the 1983-1986 NA 3.8, not the distrubitorless ignition system we use. The SC timing chain is very durable and has a good tensioner. I've never seen one fail or stretch to the point that it caused a problem with engine performance.

David
Doesn't the 89+ NA 3.8 have a similar timing chain and tensioner? I once inquired at the dealer about replacing the timing chain in my NA and was told that it was not required.

scbird1
02-09-2005, 05:40 PM
Yes you are correct they are the same as I remember rebuilding my 93 LX.
I have never replaced one on a 3.8, only the tensioner