Question about 2000 Pontiac Grand Prix

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2000Pontiac grand prix, code 304 misfire #4. Changed the spark plugs, wires, control unit for the plugs and the back 3 injectors, still have the same problem. Clear the code, comes back. slight ruff idle, but no problem acelerating. Check engine light flashes sometimes as I cruise and sometimes as I stop. had the injectors prof. cleaned, ran great for 5 mn, then came back. Any suggestions?

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Posted on Jan 02, 2017

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SOURCE: cylinder 3 misfire

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

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SOURCE: I am getting a misfire

Here is a copy of the "Policy Adjustment" that I took to the dealer with me this morning. Hope this helps any of you.

Subject: Special Policy Adjustment - Catalytic Converter #05551 -(09/14/2005)
Some customers of 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; and Buick Regal model vehicles, equipped with a 3.4L (RPO LA1 - VIN E) or 3.8L (RPO L36 - VIN K) V6 engine, may experience a condition where the vehicle exhaust catalytic converter is replaced due to complaints of lack of power or illumination of the Malfunction Indicator Lamp (MIL). This may be due to the front endcone insulation from the catalytic converter breaking away and blocking the front of the first catalyst brick and preventing the free flow of exhaust gas through the converter.
Special Policy Adjustment
This special policy covers the condition described above for a period of 10 years or 120,000 miles (190,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the customer.
For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after September 15, 2005 are covered by this special policy and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to September 15, 2005 must be submitted to the Service Contract provider.
Vehicles Involved
Involved are all 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; Buick Regal model vehicles, equipped with a 3.4L (RPO LA1 - VIN E) or 3.8L (RPO L36 - VIN K) V6 engine and built within the following VIN breakpoints:
Monte Carlo
Grand Prix
Monte Carlo
Grand Prix
Parts Information
Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO).
Part Number
Qty/ Vehicle
Converter, Catalytic (L36 engine)
Converter, Catalytic (LA1 engine)
Gasket, Catalytic Converter (Converter to I-Pipe, both)
Gasket, Exh Manif Pipe (L36)
Gasket, Exh Manif Pip (LA1)
Customer Notification
General Motors will notify customers of this special policy on their vehicles (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly).
Service Procedure
Catalytic Converter Inspection
Begin the inspection by reviewing the condition described by the customer. Refer to "Description and Operation," SI document 657895, to help you determine the correct symptom diagnostic procedure when a malfunction exists.

Posted on Feb 08, 2009

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SOURCE: 3.1 engine 96 misfires trough driving speeds and idle

i had a 94 that ran into problems like that with very rough idles and misses. i get about five different codes from injectors to oxygen sensor. turned out my negative wire from the battery was so corroded inside the insulation it was causing all sorts of problems. bought new cable and ends from canadian tire $40.00 and installed (had to clean the connection to the block with sand paper) but fixed all my problems after that.


Posted on Apr 17, 2009

  • 26 Answers

SOURCE: Engine misfires under load when warmed up.

check the mass air flow sensor, does it idle back and forth between 500-1000 rpms? if yes mass air flow sensor is the problem.

Posted on Jul 04, 2009

SOURCE: Car coded yesterday p0303 noe check engine light flashing

The only thing left is the injector or a vacuum leak on the manifold gasket sucking air in and causing a lean condition. Thats is its the only common issue providing you dont have a head gasket issue leaking coolant on that cylinder and the compression and valves are not leaking. The old spark plug should show a coolant issue if present. The white part will be shiney if you have a coolant loss. If the coolant is looking real dark you should have the cooling system checked for gas being pushed into the cooling system on compression stroke thru the head gasket.

Posted on Nov 12, 2009

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I have a 2000 Dodge Dakota and has a 3.9. It's giving a p 304 code. Runs really really rough. valves rattle and everything. put seafoam cleaner through it ran it down the road and has stopped. Had the

DTC P0304: Cylinder 4 misfire detected. Probable cause:
1. Check for latest control unit software update
2. Faulty PCM or ECM
3. Fuel injector(s) faulty
4. Ignition system fault. Check ignition module, coil, spark plugs, and wires
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Dec 09, 2014 | Dodge Cars & Trucks

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Engine lite on--code 304--also reader says-- cylinder 4 misfire--multiple

Could be a spark plug or fuel injector. Replace the spark plug first because it's cheaper. Is the car making any strange noises or doing anything unusual?

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Engine lite on--code 304--also reader says-- cylinder 4 misfire--multiple

misfires can be from the ignition circuit ( coil/s HT leads -plugs) and it can also be from injectors (low fuel pressure -faulty injectors - leaking injector washers --wiring to injectors).

Apr 12, 2014 | 2007 Saturn ION-2 Quad Coupe

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My 2000 astrovan has misfire shows code 3oo and 304

Have you cleared the codes since replacing the parts? If so, are the codes coming back? Does the misfire still exist even after replacing the parts? You post is rather unclear on this.

Feb 24, 2013 | 2000 Chevrolet Astro

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I have a 1996 ford contour i get the 304 code mice fire on cyl 4. i changed the plugs and the coil and they wires look good but the car is still sputtering and it back fired once. any ideas?

If you changed the plug, wire and coil and it didn't clear the misfire, then I would look at the injector. try switching it with another and see if the misfire code moves to the cylinder that you put the suspect injector in.

Jun 18, 2011 | Ford Contour Cars & Trucks

2 Answers

Check engine light on . will not pass DEQ code po 304

hoopers51, Code 304 is for a misfire detected on cylinder #4. Check the wire and the spark plug for that cylinder. Make sure that there is no corrosion in the boots of the wire and see if the spark plug is fouled up, or wet with gas. If the plug is fouled (a normal firing plug will have a grayish color to it) clean it and replace it. If the wire is bad then replace it. Make sure that there is no corrosion on the coil terminal when you pull the wire off. You might want to test the coil if you have an inline spark tester. These can be purchased very cheaply at any auto part store. Also what you can try is to remove the plug on the #4 injector when the engine is running. DO NOT try this with the spark plug wire. (Do this when the engine is off) When you disconnect the injector you will hear a misfire if it is working properly and this will tell you that the injector is not the problem. If there is no change then you should check for power to the injector. (once again, when the engine is running) The injector on that cylinder may be weak and is leaking. This will dump too much fuel into that cylinder causing the misfire and you will have a wet spark plug. All of these, a bad wire, a bad spark plug, a leaky injector or one with no power, or a bad coil will cause a misfire and will increase the HC's on an emission test. Good luck with this.

May 25, 2011 | Plymouth Breeze Cars & Trucks

1 Answer

2006 pontiac grand prix recevied code P0303, changed spark plugs, wires, and fuel injector. Car still shakes and check enigine light is still on. Acceleration is fine.

Spark plugs,wires and injectors, have nothing to do with your problem

PO303 is a misfire on cylinder #3
You may have an individual cylinder coil for that cyl or a coil pack for
several cyl,don't know the engine you have.

You may also have other issues that are causing the shaking

Nov 28, 2010 | 2006 Pontiac Grand Prix

1 Answer

2002 grand prix 3.1 code says number 6 cylinder misfire detetected. I changed the coil pack spark plug and wire and alSo changed the board tat the coil sets on. Computer stillsays #6 misfire detected. The...

It's a possibility the injector is the problem. It may not have the psi it needs, therefore the cylinder could be misfiring, or the injector could be letting too much fuel in. Before I change the injector, I would try to have someone to clean the injection system to see how it works. The cleaning around in South Carolina is $99-$149 depending on where you go.

Jul 04, 2010 | 2002 Pontiac Grand Prix

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

#4 cyl misfires/code 304

P-0304 indicates number 4 cylinder misfire. Are you using Toyota parts dept spark plugs? More often than not, non-toyota plugs make the v-6s run poor, right out of the box....
Try this:With the engine running, pull the connector wire off of the #4 injector. Note to see if there is any change with the idle quality. No change? You may have a bad injector.

Aug 12, 2008 | 1997 Toyota Tacoma

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