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1998 S1 runs sluggish and rough after full warmup, but only intermittantly

This Saturn S1 (1998) runs good most of the time but will after running for a good long time will sometimes begin chugg1ng and running rough. There is a trouble code in the computer for coolant sensor, but of course the car does not misbehave like this whenever the mechanic has been looking at it! Due to previous idling problems, which were fixed, the CPS. MAP, Throttle speed and Idle speeds sensors have been changed over a period of time this summer. This rough running seems to be a new problem. Sometime it will run rough for a few minutes and then clear up, sometimes it continues until the car is shut down and cooled off for a while. The fuel pump pressure is at 45-50 lbs - could this be the problem? Thanks in advance for any replies to this.

Reply to
Mgtaylor
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What are you waiting for? Replace the Coolant Temperature Sensor. Sounds like it is intermittently reporting a cold engine so you are getting too much fuel and it runs rough. These are known to fail often and are cheap and easy to fix.

Bob

Reply to
Bob Shuman

Thank you for your answer Bob. The coolant sensor code is gone and now I have a P0301 - missing on cylinder #1. This code only shows up when it is actually malfunctioning (random) which is why the mechanic has not seen it. According to the manual there can be a whole plethora of causes for this including spark plug, plug wire, low fuel output at injector(s), coil, emissions components, ignition weak or vacuum leak.

There are no other trouble codes so far. Could low fuel output cause this only in cylinder #1 because #1 is at the farthest point of the injector assembly from the fuel input?

Reply to
Mgtaylor

I'd guess you have a dirty connector on the fuel injector or a bad wire or plug. You can use some electronic contact cleaner to clean the connector and then see if it comes back. I'd also take a look at the ignition coil tower and all spark plug connections there too. They get corroded and can short out. You can easily remove and clean this off to remove the corrosion/growth. Could also be a head gasket leak, but I would not jump to that conclusion just yet.

Good luck.

Bob

Reply to
Bob Shuman

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