Car misfiring

1999 SATURN SL1
303,000 MILES • 4 CYL • 2WD • AUTOMATIC
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RHESHA
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When I first start the car it runs, and drives fine for a mile or two then it starts to jerk just a little then full on. The check engine light starts to flash. If I try to pick up any speed the engine ends up being revved up to 4000 rpm to try to get sixty five mph. I have had it scanned, and all i get is misfire in cylinder one. I have changed coil pack, wires and plugs, cleaned the gas tank, put a new filter on the fuel pump, and replaced the inline fuel filter. I do not know what to do now. Any new suggestions would be awesome.
Jan 29, 2018 at 11:27 AM
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ASEMASTER6371
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Remove the plugs and perform a compression test. let's make sure the engine is in good shape.


Roy
Jan 30, 2018 at 9:54 AM
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RENEE L
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Hello RHESHA,

Here is a link to an article form this site that features written step by step instructions, pictures and a video explaining how to conduct a compression test:
https://www.2carpros.com/articles/how-to-test-engine-compression

If you need further instructions or have another question please come back to the site, we are here to help.

Thank you for visiting 2CarPros.

Kindest regards,

Renee
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Jan 31, 2018 at 12:16 PM
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RHESHA
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I went last night and had the trouble codes scanned again. The results came back P300 and P340. Tonight I changed the crankshaft position sensor, and it seems to have helped some what. The printout for the P300 code suggested new injectors. The weather wasn't cold tonight so one of the factors was removed. Do you have to change all the injectors at the same time?
Jan 31, 2018 at 8:43 PM
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ASEMASTER6371
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the 300 code is for multiple missfires. the most common cause is low fuel pressure. not enough fuel is supplied to the injectors.

the 340 is for the cam sensor, not the crank sensor. make sure the timing marks are aligned correctly. one possible cause is timing marks not aligned

Roy
Jan 31, 2018 at 10:44 PM
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RHESHA
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Ok, I'll check those, and see that both of those are right.
Feb 2, 2018 at 11:38 AM
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ASEMASTER6371
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Ok, let us know the results

Roy
Feb 2, 2018 at 3:10 PM