Fuel System Treatments? - Ford Mustang Forum
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post #1 of 5 (permalink) Old 10-09-2018 Thread Starter
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Thumbs up Fuel System Treatments?

Greetings Gents.

Been running a little rough at idle off and on the last few months, so I figured I would run a fuel treatment in to see it makes a difference. My rpms drop to down to around 500 for about 2 seconds, then kick back up to about 1100, then settle at 900 where it should be. Doesn't happen every time I'm at idle though. This happens either at start-up, or when I'm on the road and come to a stop. But there are days that it idles right at 850 to 900 at startup and throughout my drive without dropping.

Every electrical part under the hood has been replaced in the last year except the Distributor. Also, the Fuel Pump, Filter and the Timing have been changed.

Do you all have any specific treatments you tried and noticed a difference that you can shoot my way?

LH :

87' 2.3L
5 Speed Manual

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post #2 of 5 (permalink) Old 10-10-2018
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Being in SoCal I/we deal with different blends of fuel all year round..... like now, we have been running the "winter blend" for several weeks...the temp was still in the 80's, none of our cars liked it....the older the worst it was... and the variable idle speed is common with this as if it detects a miss it will then raise the idle so it will not stall...… what I do after all these years is to add acetone to the fuel.... my base add is 1 ounce per gallon..... it won't hurt any of the sensors/cats/etc, and it works......it will also clean the fuel pump/sending unit if it gets contaminated with fuel that has high sulphur levels (as to replacing the pump as the oe's recommend)….. with the latest round I had to jump up to 2 ounces per gallon to eliminate the issue but all is well......and like I said, we deal with this all the time.

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post #3 of 5 (permalink) Old 10-11-2018
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There are a couple of things that you can do to stabilize your idle, that come to mind.

Removing and cleaning the throttle body would be at the top of my list of things to do, along with clearing the ports for the idle air control valve as well. After those parts have been thoroughly cleaned, it would be a good idea to re-adjust the base idle speed: I set mine at 750 RPM with the idle control valve plug disconnected. When your car is warmed, you should be able to unplug the Idle control valve and your engine should stay close to 700-750 RPM. If not, adjust the idle stop screw.

The PCV valve can also contribute to a wavering idle speed if it's worn out. If you haven't done so already, increasing the base spark advance on your car, will make a substantial difference in both power and idle stability; I would suggest 16-18 degree of initial advance; (set with the spout connector unplugged.)

Double check vacuum lines, it is easy to miss one. Some mechanics like to use smoke detection, but a good end to end visual check will usually do.

Let us know what you find.

89' Mustang convertible, high compression N/A 2.3.

85' SVO under s l o w deconstruction.

93' hatch currently under development

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post #4 of 5 (permalink) Old 10-17-2018
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Joined: Aug 2018
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I have an 87 GN that unfortunately sits more than it gets driven so once a year I will go to Home Depot and get a gallon of Xylene (in the paint section) and drive it to the gas station as close to E as I can. Have you a long funnel handy and put the whole can of Xylene in the tank followed by 3 gallons of premium fuel. It will clean everything from the tank to the injectors and even the valves incredibly well...it also changes the effective octane rating to about 110 in this mixture. Drive to empty, more than a few WOT passes....refuel and add some marvel mystery oil to the tank to re-lube things.
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post #5 of 5 (permalink) Old 10-17-2018
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Joined: Nov 2013
Location: Lynchburg
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I had some experience with Xylene. I spent most of my life in north central Ohio and always had a winter car. In 1978 I had a late model Corvette and a 66 Rambler I used for the winter. We got the mother of all blizzards that winter and were stranded in the plant for 3 days. Some co-workers with 4 wheel drives drug our cars into the plant to thaw out. When I went back to get the old Rambler it rattled like mad and quit running. I had it towed and ended up putting in another motor. A couple months later a colleague told me, proudly, that he had got my car started by pouring Xylene in the carburetor. I guess the old gal couldn’t stand the prosperity of having a taste of “high octane” fuel.
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