On Friday I had four separate things go wrong, all at the same time, with essentially no warning. It feels like they have to be interrelated; as bad as some of my cars have been, I've never had four simultaneous mechanical failures. In descending order of importance:


1. The engine has a horrible idle which feels like one cylinder is misfiring. There's no CEL showing, but I know from my wife's pickup that sometimes the light won't light in this situation.


2. The transmission shifts brutally into second and third. Downshifts are perfect, and so is the shift from third to fourth. When I first got the car, it didn't like to downshift into first. I added fluid, which fixed it. There is no issue with that downshift now.


3. The DoD is off. (To the guys who claim deactivating the DoD actually improves MPG--I have the DIC proof otherwise.


4. The traction control turns on and off.


Are these interrelated? Where do I start?

 

They could be Related and sounds like there is an issue with some Wiring somewhere. I would look over on top of the Transmission area where the wires are and see if there are any that have been damaged and might be shorting out on the motor or transmission. You might want to even look from the drivers wheel area with the wheel moved to the front facing the passenger side You might get a better view of the wires at that point.

I am not saying this is your issue. Just that with what your talking about and how fast or much things went wrong it sounds like a Wiring issue.

James

 

I moved the wheel and can't see any wires. Where exactly should I be looking?

 

Sorry I guess I should have gave more info.

So looking at the top of the motor on the right hand side there is your Intake, Under your intake is your transmission and other parts. There are loads of wires in that area going to the Airbox for some that go to the ECM/PCM and others that go around to other things. It can be tight under there and hard to get a good look at the wring that is close to the Transmission. At times I have seen a few different cars that have had some issues in this area. Most times with trouble shooting from the top looking for shorts and opens, I would take the bunch of wires that are under there, move them around some and at times I could get it to produce the issue that the car was having. Be it a Monte Carlo or Even same issue with a few Impalas. Then the problem is there is really very little room to get to things without removing a load of things from the car. So I found it was easier to just Move or even remove the wheel, and remove the cover in the wheel well and then there is great access to that area.

A few times I found wires that were shorting out when the car would hit bumps or what not and when I was able to look down under there. I found there was a strand of wires that the loom and wire became exposed would short to ground at different times.

Sorry I was trying to give some basic help on what may be helpful if you needed to track some more wiring on how one might get to it without moving a bunch of parts from the motor.

 

Don't apologize, I appreciate the help.

Paid a garage $40 for a diag. Turns out my CEL is burned out, and I have three codes, O2 sensor and a misfire on cylinder 7. I've already purchased a spark plug. Is there a brand of coil that's better than Delphi, or should I just go OEM?

They are sure the DoD and traction control problem will go away with the misfire. They don't have an opinion on the trasnmission concern. I'll keeo everyone posted, and thanks again.

 

You only bought one spark plug? If the plug really did go bad (unless it was a premature failure due to manufacturing defect), then I'd think it would be best to do them all. Also, are you certain it isn't the wire? Modern plugs don't usually go bad unless you've got a lot of mileage on them.

If you're replacing the coil, just get a stock one. They're extremely reliable and plenty powerful. If you aren't certain the coil is bad, maybe try swapping it to see if it moves?

I can definitely see a dead cylinder keeping it out of DOD. If it's on one of the 4 'always on' cylinders, that would make it run like complete garbage in DOD mode, so that should clear up.

As far as the transmission, try taking it to a trans shop. The 4t65 is common as dirt, any trans shop should be able to tell you pretty quick what it's going to cost to fix (unless of course it's got a zillion miles, then they'll probably just suggest a rebuild).
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I am going to replace all the plugs. What I'm not going to do is replace all eight, on the same day, in 90 degree weather, with a bad heart. (I also can't afford all eight coils at the same time.)

 

The problem is solved, for a grand total of $12. ($2 for a plug, $10 for a fish tank siphon at Wal-Mart to yield the plastic tubing I needed to put the new plug in the invisible hole. Thank you, YouTube.)

The coil was fine, the wire was fine, the plug looked like it had been hit with a flamethrower. All the problems are now solved, including the rough shift. The one thing I did discover (besides the plastic tube thing) is that the old plugs were Bosch, and were apparently only good for 50K miles. No more for me.