Question about 1999 Pontiac Grand Am GT

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Cylinder 3 misfire

I have a 99 pontiac grand am i ran the obd 2 on it and it keeps coming up multiple cylinder misfire. i have replaced the spark plugs, the coils, the o2 sensor,fuel injectors,the boots, crankshaft position sensor,catalytic converter,fuel filter,the tps,idle air control and amongst other things can you please help me

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  • workingr Jul 17, 2008

    mine started doing the same thing Saturday, I replaced the plugs, plug boots, coil packs and ignition control module, still misfiring. You get your figured out yet? I think its the computer.

  • Anonymous May 13, 2009

    I have replaced everything you have and still cannot figure out my issue.... My intake manifold gaskets are new as well.

  • Anonymous Mar 15, 2014

    changed plugs,coils,insulaters and injectors , but still runs rough

  • Anonymous Mar 23, 2014

    replaced injectors fuel filter spark plugs have 61 psi fuel press

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Make sure you're using the recommended spark plugs. When my car did that, I had put Bosch Platinum Plus-4 plugs in and got that same problem. Turns out the plugs are too hot and cause it to fire prematurely and kick the misfire code.

Posted on Jul 24, 2008

  • holva dalmasi
    holva dalmasi Jan 20, 2014

    when you changed the spark plugs to the right ones did it work?

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Wow man! you change a lot of stuff, it ain't better to buy a new car?

Posted on Jun 17, 2008

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Misfiring on cylinder #3


Misfiring can be cause by ignition coil,spark plugs,wires,engine valve,cylinder compression,
if it's a quad four then crack around the ignition coil. there is 2 coils like 1-4 coil and 2-3 coil
first check spark plug color or foul of gaz
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My girlfriend has a 99 pontiac grand am with the 2.4 l an has a cylinder number 2 misfire .. it spits an spudders out exhaust any ideas where to start ?


Plugs, a coil tower, and four spark plug boots would be a good start. Wery common for the towers to go bad on these.

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My 2000 grand am has multiple miss fires


P0300 Diagnostic Code - Random/Multiple Cylinder Misfire Detected

Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.

A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

Symptoms may include:
* the engine may be harder to start
* the engine may stumble / stumble, and/or hesitate
* other symptoms may also be present

Causes: A code P0300 may mean that one or more of the following has happened:
* Faulty spark plugs or wires
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector(s)
* Burned exhaust valve
* Faulty catalytic converter(s)
* Stuck/blocked EGR valve / passages
* Faulty camshaft position sensor
* Defective computer

Possible Solutions:
- If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
- If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.


Hope helps, and keep us updated.

Jan 05, 2011 | 2000 Pontiac Grand Am GT

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1999 grand prix gt 3.8v 6 error codes 300 and 302


The PO300 code is random/multiple cylinder misfire detected. Sinsc you have the code PO302, that means that cylinder 2 is the one misfiring, usually a bad coil pack, or spark plug.

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I have a 99 grand am SE 2.4 4 cylinder and my problem #2 misfire, repalced spark plugs with AC delco rapid fires, replaced coil packs, replaced coil pack housing, changed spark plug boots, had ignition...


A misfire doesn't always have to be ignition... it's just the most common cause. Faulty or plugged injector, low compression. You need to check fuel pressure and test the fuel injector flow. Then check compression. If you don't have tools for these tests, take it to someone who does. Testing is much cheaper than throwing parts at the problem.

Feb 25, 2010 | 1999 Pontiac Grand Am GT

1 Answer

I ran a scanner on my 2002 pontiac grand prix 3100 V6 and it reads out as multiple misfire i already changed the spark plugs,what could the problem be?


A code “multiple misfire” may mean that one or more of the following has happened:

•Faulty spark plugs or wires
•Faulty coil (pack)
•Faulty oxygen sensor(s)
•Faulty fuel injector(s)
•Burned exhaust valve
•Faulty catalytic converter(s)
•Stuck/blocked EGR valve / passages
•Faulty camshaft position sensor
•Defective computer

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

Feb 01, 2010 | 2002 Pontiac Grand Prix

2 Answers

1996 Pont Grand Prix ---- P0303 again & again


The Specific code "P0303" is stating that the Third Cylinder or Cylinder number 3 Is mis-firing, thanks to all that you have done this has narrowed it down to two "confirmed" possible problems;

The first is that the Exhaust VALVE itself may be "Burned" and the Second may be a Poor condition or "Faulty" Catalytic converter(s).

This is only a possible cause but please keep in mind that on some certain models (not too sure about this specific model) there are multiple O2 Sensors located in different spots. (usually in or next to the preliminary and primary catalytic converts)

Also one of my experiences lead me to beleive that the Ignition Control Module (ICM) may be faulty causing the injector to not provide proper Fuel to the Cylinder.which will more often than not cause the computer chip to sense the misfiring as opposed to the bad signal from the ICM.

Hope it helps you out, and good luck.

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Check the plug wires for those 2 cylinders, next check the injectors, as they can cause misfire when defective.

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