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How Do I Fix & Preserve Carb Vac To Maintain CRX HF MPG?

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How Do I Fix & Preserve Carb Vac To Maintain CRX HF MPG?

Postby ascendedmind » Fri Mar 18, 2016 2:54 pm

Hi, I just bought a 1985 Honda CRX HF 1.5 with 3 barrel carburetor. Everything is original & stock. Only has approx. 125,000 miles. I bought as an alternative to a hybrid. I really appreciate this car & working on restoring everything.

I realize this is a Honda CRX Performance forum, however I bought this version for High Fuel Economy & not for performance. Fans of the HF say don't devac if you want to maintain or keep the same MPG rating. In other words keep it stock.

Presently the carb or insulator base plate gasket has a noticeable vacuum leak verified with carb cleaner.

When started cold it idles approx. at 2350 RPM then when it warms up kicks down to about 1350 RPM.
Now at what speed should the motor be idling at from a cold start & what idle speed when warmed?

Under hood says 650-750 RPM for HF

Do you recommend I have a professional smoke test performed on the engine to check for any & all vacuum leaks?

Note: It was recommended by Permatex & others to use Permatex Permashield Fuel Resistant gasket dressing (aka Hylomar Universal Blue( which is Non-Hardening & Non-setting as a solution for the carburetor insulator or base plate gasket. If gasket is salvageable then use together with the Permashield.

Please don't recommend devac or replacing with Weber as I'm not interested in performance. I do have a brand new Honda Service Manual for my 1985 Honda Civic CRX ( HF model). But I'm not mechanically inclined, but can read & follow directions.

Any suggestions for finding a capable or good Honda mechanic in the Pacific NorthWest? I live in the Seattle-Tacoma area in Puyallup by the State Fair.

However, I may be forced to learn this.

Any special tools I definitely need to get? I bought a carburetor rebuild kit, float kit & purchased the last Needle & Valve from Honda.
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Re: How Do I Fix & Preserve Carb Vac To Maintain CRX HF MPG?

Postby windraver » Fri Mar 18, 2016 7:24 pm

Hello and welcome!

I wouldn't necessarily say that everyone here is "performance minded". I for one did my "D15Z1" Civic VX swap for its MPG value.

Unfortunately I don't have much experience with the carb 1g HF. Vaccum leaks generally requires slow and steady and structured analysis.

Smoke test is certainly an option but I've never done it and thus can't compare against it. If you've found a leak, then I suggest sealing it. If you're taking apart enough parts and you have the budget/time, then I would further suggest you perform a rebuild. Whether a rebuild of the engine, carb, intake, or even new vacuum lines, these things add up to better MPG.

A few sites I might also suggest that specialize in MPG:

And then 1G specialization:

Finally, it depends on what you need to do to determine what tools you need. Start with fixing what you know is broken and go from there. Might be good to correct that idle too.
I just noticed I'm never playing by the rules
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