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Question from Dave:
In the process of doing some general maintenance on my 1981 EFI. I have removed the support plate to get access to egr valve, and it is clear that some of the potting material from the fuel flow meter and computer has flowed into the throttle body. While there are still pools of material on the support plate, the throttle definitely needs cleaning and at least one injector is coated with black goo.
Does anyone have a suggestion for cleaning the goo off the plate (thought I would start with "Goo Gone")? I am already replacing the spacer assembly between the intake manifold and throttle body... but how worried do you think I should be about cleaning this out of the intake manifold too?
I cleaned the inside of my 82 EFI Imperial assmbley with a lot of spray carbureter cleaner and a little screwdriver to pick at it. I got most of it out but it took a couple of hours.
Certainly, you need to clean this glop out of any area where it can interfere with the throttle butterfly, and clean it off the fuel rail nozzle area. If one or more of the nozzles is plugged up, your performance will be affected significantly. I don't see much hazard in leaving some of it down in the intake manifold.
The spacer between the support plate and the intake manifold is extremely critical as to sealing to both mating parts, and the gaskets are complex and delicate. If you feel you must replace these, try to get NOS ones, or at least be careful to save the originals and inspect them carefully. Any air leak here, even very slight, will really screw up the way the car idles.
Nothing I have found is a magic elixir for dissolving the goop, I think acetone is very good, but you must be careful around any non-metallic parts, as it very likely will attack those too. Lacquer thinner and Carburetor cleaner are some help. Also, but basic grunt work (scraping, peeling, gouging etc.) is what we are all reduced to sooner or later.
Follow-up question from Kurt:
Oddly enough, I am doing the same thing to my 81, but haven't yet taken off the support plate. I'm trying to get at the EGR as well. All I want to do is replace the EGR valve and clean off any carbon deposits down there as well. Do you think it's worth it if the EGR is functioning? Re-setting the support plate may pose a problem. Did you have a new gasket or did you re-use the old? Also, what caused your meltdown? I haven't had one yet, but have a lot of old parts from junkers that did melt. Anybody think it's worth it to remove the support plate to replace a functioning EGR? Or is there another way around removing it to get at the EGR? I can't see any other way.
Reply from Bob:
Whether the EGR Valve works or not, there are two metering ports, (one for each bank of cylinders), installed in the bottom of the manifold, under the Support Plate, with small holes in them to admit gasses into the mix. If these are clogged, the whole EGR concept is worthless, moreover, the passage between the EGR Valve and these ports is usually clogged with tars, especially on high-mileage cars, and the system won't work. Not employing the EGR Valve is your choice, but if it has a defective or leaking vacuum chamber, you'll have a lean mixture and then EFI will be unable to compensate for this since it occurs after the information for the correct Fuel-Air Mix is determined. If you remove it, then use a blank plate to cover the opening.
The "melting" of the potting compound is usually from original equipment modules. If it gets into the throttle plate bores, it'll disrupt the operation. Use the same cleaner for the Throttle Plate as is used to clean the upper dish and modules. Carb cleaner and/or a similar substance. It's messy and takes time; must be done.
Reply from Dave:
I have removed the EFI support plate and used three cans of carb cleaner to remove the potting material from plate and throttle body. Both now glisten. I decided to do everything else I can now, because it's such a hassle to get the plate out. With the plate gone, you can get at the EGR valve. I took it out and reamed out the carbon using a vacuum cleaner to suck up all the little black pieces. I replaced the valve just so I wouldn't have to think about it again.
I also pulled the valve covers and painted them, cleaned up the intake manifold and painted it, put on new valve cover gaskets. For the heck of it, I also replaced the temp sending unit because it's cheap to replace and impossible to get at without taking everything apart. While I'm at it I'm also replacing most of the hoses, too, especially the fuel lines leading to the plate.
I replaced the spacer assembly with one from my local Chrysler dealer. Cost was $22.00 and it's in stock in Detroit. I absolutely replaced the foam gasket between the plate and throttle body. There is no way to remove this gasket in one piece and reuse, but it's critical to avoid air leaks. I got mine from Brad's NOS Parts (on the web) for about $13.
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