Having problems with your 2002 Pontiac Grand Am ?

Hesitation with slight throttle

\015 I have a 2002 grand am, se1 3.4l. This car is costing me some money on guess work by mechanics that can not seem to figure out my problem. At 35 mph and above my car seems to hesitate. It feels like it rocks back and forth and you can hear it winding, the RPM's jump up and down as well. But if I give it gas it will kick in O/D and take off with no problem. It only does it if I slowly press the gas down trying to get normal speed after a stop or hanging around 35mph or above. I had my tranny checked at AAMCO and they said it was not the tranny. I since had my plugs, wires, Oxygen Sensors, and fuel filter changed. I also tried my throttle position sensor and oil pressure switch. Still doing it. I also was told my middle coil pack was bad, changed that and same problem. I did not put cheap parts on there thinking i'd get better performance out of it in the long run. Now the big question is... I had my cat converter cut off, would that make it hesitate any? Some tell me not at all some say yes. I do get a code p0420... catalist efficiency below threshold (bank1) What is that? Cant be 02 sensor as they are new. The code was reset and came back on after a 45 min drive. I am lost and so are many people. I do not wanna pay Pontiac $108 for telling me there are no codes and they cant say. Any suggestions would help. Thanks.\015 Posted / edited by AnonymousUser on : 19-03-2018

Answers :

Well putting a new "cat" back on should sort it out,
\015\012what you have done by taking the "cat" off is to throw the engine manigment computer into a wobely,, its trying to get the fule mix right and it cant get the O2 mix right, so it cuts the fule mix back to fix this, however, doing that causes the throtel seconser to tell the computer it needs more fule, witch it then gets,,,back to the start again,,,02 go's right up!
\015\012the computer is having a fit, so starts to throw a "wobbely about it all!" to be blunt, its like a having a bad hair day,, or you could call it PMT, but it need to have that "cat" put back on to fix this,,and as for it taking 45 mins to tell you its not happy (ie po420 coad) its trying to be polite, your lucky it never just shut down on you and went into "get you home mode!" thats like 5 mpg at 30mph top's!!!!!!!!
\015\012till you fix it right,,,tell me why did you try to take off the cat??? it realy wont run right with out it, and the very fuw mpg you may have saved just just cost you twice that pluss all the agro to boot!
Repair Help & Product Troubleshooting for 2002 Pontiac Grand Am

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