Cylinder Misfire and OBD-2 Codes

**jmcc1071** · 05-01-2013

I have a 98 Grand Prix SE 3.1 and I'm just about at wits end with it. I recently replaced plugs and wires to try and fix a bad idle/choppy acceleration and it did nothing to solve it. So next on the list was to replace the intake gaskets. Did that. Before was only showing OBD-2 codes P0303 (Cyl 3 mis), but after putting the motor back together, I still have the same problem and it now shows P0303 again as well as P0122 (Throttle/Pedal position sensor circuit low input) and P0102 ( Mass or volume air flow ciruit low input).

Side note: While I had the fuel rail off I inspected the injectors and found that a few of them were clean and appeared to have no wear, and the O-ring on 5 was busted so we replaced and greased them all.

Anything that could help would be greatly appreciated because I don't want to spend any more time or money that I don't have to.

**Iceman6669** · 05-01-2013

Did you try the coils to see if that fixes your miss? The TPS sensor code could just be that it needs to be re-installed, I had the same issue when I took mine out... The p0102 I have no idea on.

**jmcc1071** · 05-02-2013

Okay, so I just tried a new coil pack and swapped it out for all the old coils and got the same problem each time.

**dbextreme** · 05-02-2013

Pull the plug on #3. Put the plug in the wire, hold the wire by the boot and ground the threads of the plug on a mount. Have someone start the car to make sure that plug is getting fire. You should have a nice bright white spark coming from the plug. (sounds weird to do, it's how I do it without getting shocked... LOL) The other way you can pull the wire and put a screw driver in the boot touching the metal. Hold the boot and the handle of the screw driver placing the metal shaft of the screw driver close to a piece of metal. Have someone start the car, see if you have spark arching from the screw driver shaft to the piece of metal it's close to.

If you don't have spark, it could be a faulty ICM.

If you have spark, clean the MAF and TPS with MAF cleaner while checking all your electrical connections to the parts. Also, it may sound crazy, but check your EGR. I had this issue on another type vehicle and it was the EGR valve.

**jmcc1071** · 05-02-2013

We disconnected the EGR while it was running and there was no change in the symptoms.

**jmcc1071** · 05-04-2013

Took off the ICM and had it tested, and took the wires off and have arcing across each coil pack. So ruling out the ICM and coils, anyone have any ideas?