Question about 2000 Pontiac Bonneville

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Car coded yesterday p0303 noe check engine light flashing

Car coded yesterday p0303 which said misfire in cylinder 3. if you cold start car it runs fine. But if you stop and restart it idles rough, runs crummy and then the check engine light flashes. recently replaced plugs, wires and coil packs..All help appreciated.Thanks.

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  • kellster743 Nov 12, 2009

    OK took it to a shop. Says injector is bad. Also says he has to clean the other 5 injectors?So an $80 part turns into a $500 repair?Really?


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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

  • Ernset ( Skip ) Bouvette

    we charge $120 to do an injector service. The part does cost a set price but we would do a service first hoping it woulld clean up the bad injector. If it did not then we would replace it at a cost of about an hour labor, so a diag to recommend and do a injector service after other items were ruled out would be about $200. Then to replace the injector would be cost of part, say $80 and labor, say $100 ....$500 does seem a little steep but really not out of range if you like and trust your mechanic.


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Try checking the knock sensor and clean the throttle plate inside and out and also the back of the throttle plae, many times the plate sticks from back firing that you can't detect by ear or feel. Also could have a plugged cay.

Posted on Nov 12, 2009

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  • Bruce Hathcock Nov 12, 2009

    The injector you could of replaced and the cleaning the other injectors is easy buy lucas gas treatment for 12.95 and put it in a tank of fresh preimum fuel and just have them replace the one and walk away. you did not rate me are you upset at me? The shop is hungry, the price is silly. But be aware that you may need new injectors down the road, the best solution is to replace them. However with one bad injector if it blows up your engine is destroyed Jsut remember that.

  • Bruce Hathcock Nov 13, 2009

    You can find it in most parts store orilys formally schucks or autozone or if you can'yt find iit there check walmart on line or any oil jobber in your aera or a Transmisson shop will carry it for transmissons and gas I would bet but if you don't find it let me know and give me your zip and I will look it up for you. I wanted to add that the injecter being defective could destroy the cat. If you continue driveing it, thats why you have the flashing check engine light. And be aware that if one injector is bad the others are not to far behind Like the other expert said $80.00 for the hook up of scanner is normal shop time and remove and replace the injector is $100.00 and injector is $80.00 so $280.00 is about right but if he is going to remove and clean the other injectors I would rather he replace then I know it is expensive but if the injecter dies it could destroy the engine, so you will have to weigh that into account, If you are going to keep the car then try to plan to replace then all as soon as yo can. Since the fuel rail is charged with up to 50 PSI if the inecter goes south (Fails) it can wash out the cylinder and destroy the cylinder or crank or both and will cost you a new engine. The price to do the repair right would equal 2 to 3 car payments. compared to buying a new car. Thanks for rating sir and I suggest you look at our profiles and or expertise and read other suggestions on manitence as well. It could save you before hand, And thanks for rating us sir.


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A code P0303 may mean that one or more of the following has happened:

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