2001 Grand Am problems


#1

We bought a used 2001 Grand Am (V6 automatic) a few months ago. Mileage was just under 100,000. It was running decently at first, but that improved once we did more maintenance. It’s gone from about 150 miles on the highway on a full tank to about 250. A lot of the problems didn’t reveal themselves until we took it onto the highways. These are the parts we changed in the last 2 months:

-new battery (old one was 0.1 above fail)
-all 6 spark plugs
-catalytic converter
-front oxygen sensor
-oil filter
-timing belt
-pcv valve and breather hose (old one melted)
-all 4 shocks/struts

Latest problem is OBD code P0301 cylinder #1 misfire. The entire car started to shake when we were in low speed in a drive thru. It only seems to shake in drive gear and it does it the whole time. It doesn’t shake in reverse or any other gear. Found out #1 spark plug was cracked and a chunk of the ceramic portion was missing. It got replaced but that didn’t fix the problem. Haven’t noticed any white exhaust yet. The ignition fails 1/7 of the time since P0301surfaced.

The last problem we had was P0420. We went to 3 different shops and nobody was able to fix the problem properly. It wasn’t until the pcv valve and breather hose were replaced that the code disappeared. The valve was actually cracked and parts of the breather hose were melted. I can’t understand why nobody noticed that.

I know there could be a lot going on, but I was hoping the possible problem could be narrowed down. Has anyone had similar problems?


#2

“The ignition fails 1/7 of the time…”

What does that mean?

If the spark plug insulator was cracked and possibly arcing, that may in turn have damaged a coil. Try replacing the coil that fires #1 plug.


#3

The fact that it misfires in drive but not reverse makes me suspect a bad ground or other wiring problem. When you are in drive the engine twists one way on the mounts but when in reverse it twists the other. This pulls on the wiring harnesses in two different directions. Sometimes a wire can look good but be broken inside the insulation.


#4

Timing belt?