Rough Idle and Car Simply Not Running Right
 

986 Boxster MY99 55K miles

Hello. I'm having some idle and rough-running issues. As my car is sitting in traffic, the idle fluctuates just a bit between 800-1000 rpm. Not a big deal as far as I know. Might it be a dirty throttle body? I recently had a tuneup completed: new plugs, filters, etc. I also recently added Red Line's fuel system cleaner and since then, my car seems as though it doesn't run as well as before. I've heard others say it's a good idea to change your oil soon after adding cleaner, but my mechanic said that it's unnecessary. I just find it odd that the car runs worse AFTER adding the cleaner.

Finally - and please pardon my ignorance - I also have a bottle of Swepco 503 cleaner. Would it be unnecessary - or even dangerous - to add that as well, considering that I just added the Red Line? I've been trying to educated myself as much as possible about my new toy, but I obviously have a long way to go. Many thanks for any suggestions.

How much gas is in it right now?
Randy

And what brand of gas?

It has almost a full tank of Chevron 89 octane (the highest I can get where I live). I dumped a bottle of Red Line into the tank when it was around 1/4 full last week.

Ok, The very first and least expensive thing I would try is. fill it up and see how it runs. Not much point in panicing at this time. See what happens.
Randy

Do you mean top it off? There are probably still remnants of the last brand that I used, so maybe that's part of it. Thanks.

Sorry, Thought I read your poast as having less than that. Top it off or what ever and run what is in the tank out. If you have to put more gas in it along the way. So be it. Just saying. It's not time to start throwing money at it. Other than that. Get what's in it out and go from there.
Since this issue seems to have started with the red line stuff. Do not add more gas additive in it.
Randy

Understood. Thanks again.

I'd tell you to syphon it out. But been there, tried that. Got the T-Shirt. There is something in the filler tube that stops you from putting a line in it.
Don't worry at this point. Best of luck. Randy

The harsher the fuel system cleaner (or fuel injector cleaner), the more the reason to change the oil right after burning that stuff out though a tank of gas. Appears some of that stuff can slip by your rings and enter the oil, which is not good for the oil. I don't know anything about the Red Line stuff you put in there, but when I sought advice about BG44K, I was told it was imperative to do an oil change afterwards. But a bottle of Techron was more than likely not so bad. Either way, I don't use any fuel system cleaner until two tanks before my next oil change. The first tank has the cleaner in it, and the second tank just to dilute whatever cleaner is still left in the tank.

A fluctuating idle as you described could be a myriad of things. Like Randy said, burn through that tank to eliminate one of the variables. Then, if you're still having problems, continue to troubleshoot. Could be the throttle body and idle air control valve needs to be cleaned. Heck, could be the gas! When I was in AZ, I filled up my bike at a shady no-name-brand Indian reservation gas station and when I got down to about a quarter tank, parked the bike overnight, and the next day my carb floats were so gummed up that they continued to let fuel flow into the bowls until they overflowed and poured onto the ground! Talk about scared, a hot engine on a 115F day and fuel streaming out from underneath my bike. I couldn't get that bike stopped and off it fast enough. :)