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I have an 03 grand prix autozone said it was a random

Customer Question
I have an 03 grand...
I have an 03 grand prix autozone said it was a random misfire. vague! so I changed the plugs and wires and had one new coil pack to swap out between the three , no luck. so I changed the cat converter thinking it was plugged. didn't hurt but didn't fix it! what else could make it run rough even at idle?
JA: Is the rough idle intermittent or consistent?
Customer: consistent
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: yes . plugs wires and CAT
JA: Anything else you think the mechanic should know?
Customer: no
Submitted: 1 year ago.Category: Pontiac
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Answered in 4 minutes by:
8/12/2016
Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago
david craig
david craig, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 4,492
Experience: owner/mechanic at 3D Automotive
Verified

Hi Im David. the most important thing here is not to start throwing parts at your car. 1. you not sure if its going to fix it.

2. you're wasting your money and time.

3. you dont know what cylinder is misfiring.

Now you said you bought 1 new coil pack and tried swapping them betwwen the 3? there are 6.

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

it can be a coil pack, a fuel injector, a wiring issue, a bad cylinder etc....

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Customer reply replied 1 year ago
the coil packs have two points per pack for a six cylinder which makes three two point packs. and shouldn't the computer throw a code for an injector or wiring issue?
Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

my bad, thinking of a different engine. and no the computer does not throw a code for an injector fault

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

on high end scan tools you can read injector behavior and actually shut them down and back on.

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

a generic code reader is very limited.

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

and depending on if its a wiring issue to the failed cylinder component its only tell you its a misfire

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Customer reply replied 1 year ago
ok yeah I wonder how precise they were. what about the throttle position sensor? oh and it was putting of a sulfur smell!
Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

tps not the problem. that would give you a fault. sulfur huh? do a backpressure test on the cat

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Customer reply replied 1 year ago
ok I will try that. thank you . and could it be one of the sensors on the exhaust ?
Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

not making it run that bad

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Customer reply replied 1 year ago
ok so maybe just getting too much back pressure somewhere then?
Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

yep. clogged cats will do that

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Customer reply replied 1 year ago
that's what I thought so I changed it and still no change.
Customer reply replied 1 year ago
what else could be clogged enough to cause this?
Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

hang on a few

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

sorry man, got really busy yesterday at my shop. Dont take that as your issue not being important. Its hard alot of times to keep up with both. Im looking into this right now.

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

Do a compression test on all the cylinders. Before we dive into anything else, lets make sure we arent dealing with a dead cylinder. Ill be checking throughout the day for the results.

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

any progress?

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

do you still need assistance?

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Pontiac Mechanic: david craig, ASE Certified Technician replied 1 year ago

hello??????

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Pontiac Mechanic: sprinkles08, ASE Certified Technician replied 1 year ago
sprinkles08
sprinkles08, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 23,507
Experience: ASE Master and Advanced level certified. Factory trained with 17 years dealership experience
Verified

Hello and welcome to JustAnswer!

I'm assuming you had a multi cylinder misfire code set, P0300. This code sets when the engine controller is seeing misfires on more than one cylinder at a time. This could be several things.

Did the problem start not long after getting fuel?

Are yu able to feel a constant miss?
Is there any abnormal engine noise?

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Ask sprinkles08 Your Own Question
sprinkles08
sprinkles08
sprinkles08, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 23,507
23,507 Satisfied Customers
Experience: ASE Master and Advanced level certified. Factory trained with 17 years dealership experience

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