Hope this is the right place. This is my 1st post and it's for my friend's car. She has a 1998 Monte Carlo 3.1 V6. She put about $2000 into it, has taken it to PepBoys and 3-4 local garages. Wires and plugs replaced and new fuel injector. Her problem is the car misses when idleing. When she had fuel injector replaced it didn't miss for about 1 week then started again. Is the piston bad or cracked??? Any help would be appreciated. Thanks! ~Linda

 

start switching plug wires around cylinders. switch them so they are still at the corresponding cylinder. take the one that the injector was replaced and switch it with a good wire. if the miss jumps cylinders its the wire. if it doesnt switch then try swaping spark plugs. if that doesnt change it then you are looking at a injector again or a valvetrain condition.

 

check the intake for leaks oil and vacuum