vacuum advance both ports to manifold - 86 LXi

[AC439]

Hi all,

I have searched and read the few threads related to it but still I'd want some input before doing it.

The vacuum advance on the distributor was broken and has been replaced with the non-fuel injection type from rockauto (the two vacuum connections pointing downwards after installation, I know, rockauto was blaming me while their catalog is incorrect and it was a rough experience with them). Anyway, the vacuum advance was expensive and I intended to keep using it. I have put longer vacuum hoses and its been ok and working. But I think the timing is not optimized.

However, I remember reading somewhere the vacuum advance of the non-FI accord advances less compare to the FI advance. I know the one further away is for cold coolant/engine condition to add another 4 degrees. So I'm thinking why not connect both vacuum ports to manifold for the additional 4 degrees to compensate it. But I live down in FL so its always hot anyway.

I wonder if any LXi owners have done the same by connecting both vacuum advance ports to manifold vacuum and plug the vacuum pipe from the engine cold solenoid ? I have never heard a ping or knock in my entire life so I don't want to risk over advancing the spark and damage the engine. Some of you said our engine is very tolerance to knocking.

What is your thought ?

Thanks.

[Oldblueaccord]

AC somehow I missed this post so Ill bump it more than anything.

Doing what you said will add 4 degrees to cruise timing (light throttle high manifold vacuum) im guessing.

If it runs ok for you I don't see a problem. Alot of timing at steady cruise will make a motor surge alot in my experience.

My car conversely has always had some ping especially when shifting gears ever since I had it. But its EFI.

There pretty tough motors anyway. I run e85 and checking my tune with a wideband the car can easily run 16.5 or a little more in some situations and my motor is not damaged at this point.

[AC439]

Thanks for reply. I am working out of town and there is quite a bit of hwy driving. Current ignition timing only gets me to 29.5 mpg on average (80% hwy driving). I have this car for over 20 years and I recall it gave better mpg before, like over 30+. I thought my timing is not optimized, especially after installing a non-FI vacuum advance. It somehow feels the power is not as strong below 70mph (light throttle, vacuum advance on). But I can hit gas pedal harder and it will pull strong from 65-70 to 80-85 mph (mechanical advance on, vacuum advance off). Therefore, I want to tweak the vacuum advance to give a bit more performance (especially better mpg) for cruising condition.

I'm going to try the idea today and post feedback.

[Oldblueaccord]

Update?

[AC439]

I have connected both ports to port vacuum and plugged the cold advance pipe. However, I just noticed I have a brake booster vacuum leak (see my other post) and I do not notice any difference of power or mpg at this point. The car does feel sluggish especially trying to keep up with traffic on interstate. I think I will have to replace the brake booster first, then my manifold vacuum will be restored to the norminal value. Then come back to play with vacuum advance timing (use one or both ports).

[AC439]

Life has been busy but I finally have some updates. I replaced both the brake booster and the master cylinder due to leaking brake fluid into the booster. The booster was making some boiling water sound for half a min after turning car off. The old booster had a pool of dark brake fluid inside and thus it didn't hold a vacuum. The accumulated brake fluid was the source of the boiling water sound because air passed through the fluid when it leaked.

The brake is much better after the repair work and the new booster is sealed well. I just have to fine tune the brake pedal travel (now seems a little excess).

So, back to the vacuum issue. Now the booster is fixed, the manifold vacuum is higher and back to normal. I have the vacuum advance restored to the original connection (no longer connects both ports together). The car appears to have restored to previous engine response (vacuum advance works better in response to normal vacuum pressure). I am going to work out of town with a bit of highway driving and will further test responsiveness and MPG as well.

I believe when the booster was leaking, the engine was running lean so the ECU compensated by giving more fuel through the injectors. I expect my MPG will improve and will test it out in the next two days or so.

[Dr_Snooz]

Nice work. Keep us posted.

[AC439]

The first tank after the repair showed MPG improvement (around 30 from previous 27 to 27.5). I'm on my second tank but have lots of local driving lately. The engine behaves like before, feeling its power has been restored. I am very happy with the booster repair that led to normalizing the vacuum pressure.

Too bad the car wont start today at the office. A jump was not successful until moved the shift level from park all the way to 2 then back to park and it started. Not sure if this is battery problem or not. Its a Walmart battery of just 2 years new. I am connecting to a charger now but it doesnt seem to talking in much charging current....

[POS carb]

That sounds like a neutral switch issue. If the battery was bad it wouldn't just start working