88 Accord Vaccuum Lost Breaks

[asaph]

I recently had to have pull the head on my 87 accord, 2.0 carb auto.

When I put everything back together I lost the brakes. I have traced the vacuum lines, including the one from the manifold to the booster, can't find the leak.

The idle is high most of the time, but sometimes it will slow down to under 1k rpm and then try to die, and then engine run on is common.

took the car to mechanic, timing is right on, can't find prob. any suggestions?

1988 accord LX
2.0 engine
12v
auto
air
cruise
carb.

[VTEC_Inside]

Lost the brakes?

I'll assume you mean the power brakes since you also mention vacuum lines. Did you reinstall the one way valve in the hose to the booster?

[asaph]

I did not take that apart when I pulled the head off. I did disconnect the hose to check to see if I had some vacuum from the manifold side, and I did. I did get brakes one time after that, but when I stopped the car hard, the engine stalled. After that the brakes were gone again.

[A20A1]

What is your vacuum reading?

24" hg ???

If you removed the intake manifold from the head, check your intake manifold gasket and buy a new one if you didn't replace the old gasket.

Check you PCV valve.

Check your valve timing not just ignition timing.
Also set ignition timing with ignition advance disable.

Make sure your throttle cable is not too tight and that the throttle isn't open too far, you want to be sure you're on the idle circuit .

What is your idle speed when the car is fully warm?


What speed does your car idle when you shut it off... usually high idle will cause the car to diesel / run-on .
...also ignition timing can sometimes cause that too, I dunno if valve timing can cause that, but I'm sure it may have some effect.


Low vacuum can cause your idle diaphragm / throttle controller to go wacky and raise the idle more and more and you'll get dieseling... part of the reason would be that you are relying to heavily on the throttle controler adjustment... meaning you adjusted the screw too far in to make up for the low vacuum and thats how you have the such an unstable idle.

Find the vacuum leak or adjust the ignition/valve timing, again make sure nothing is holding open your throttle like the throttle cable.
Don't adjust the throttle stop screw unless you touched it after removing the head.

If your head was causing poor idle and you adjusted the carb to compensate, you'll probably have to readjust the carb anyways now that the head or gasket or whatever you did is fixed.




--- But currently I'm leaning towards vacuum leak & bad throttle controller adjustment.

[asaph]

I do not have a gage, I have taken the car to a mechanic so they will have to check that.

I did remove the manifold, and replaced the gasket.

valve timing vs ignition timing...are you talking about the relationship between the head and block. If so, when I installed the head, the marks on the cam sprocket lined up with the top of the head on both sides, and the block was at TDC on the compression stroke.

ignition timing was checked by me while engine warm at about 1200 rpm or a bit faster, and advance hoses removed and capped.

idle speed when fully warm has been as high as 2000 and as low as about 850 very rough.

I don't have the car right now, the mechanic is going to take it to another shop tomorrow dedicated to Japanese cars as he cannot find the problem.

When I get the high idle I do get the deiseling problem.

[asaph]

I forgot to say I had only had the car for about three weeks when the head gasket ruptured. I got it really cheap, and it ran great except that it shook at low idle like it needed new motor mounts.

I had not touched anything when the gasket blew. I never touched the carb before and I don't know if the previous owner did.

[A20A1]

hrm, that makes things worse. :)

Might want to check your primary booster venturi as well, thought that would cause a slight studder on accleration or poor accleration.

Do you have any suspicions as to why the gasket blew?

Running lean?

BTW 1200 RPM is too high an idle when the car is fully warm, it should be closer to 1000 but high enough so that when you drop the car in gear (AUTO) the idle will be steady.

[asaph]

I am not sure why the gasket blew. I think after I looked at the engine bay in more detail as I was doing the tear down that it had been hot before I bought it. I was even more sure of it when I pulled the water pump and it was almost brand new and the gaskets on the thermostat were new.

It had probably overheated and had some patch work done and I got it just before the end.

The idle does try to drop down, but when it does it is iffy. The idle was fine before except for the shake, and the motor mounts were trashed so I chalked it up to that. I am leaning still to it being a vacuum leak, but I have not been able to find it.

btw... was I right about what you called valve timing?

[Honda-Master]

yo A20A1 why do you always tell people to set timing with vacc advance disabled??? you are supposed to leave hoses as they are.. if you remove hose from advance diaphram you will retard the timing if you set it this way once you plug the vacc hose back in timing will be advanced ,, hose # 2 inner hose at vacc advance is supposed to have vacc all the time and you set timing with hose connected ,,,

[Honda-Master]

asaph,,,,,, is the brake pedal hard?? when u step on brakes with car running do you hear a hissing noise ?? if so booster is leaking ,,it would also make engine run rough at idle ..... and as for setting the timing 1200 rpm is too high it should be set at 750-800 rpm with hoses connected at vacc advance and make sure u get vacc at inner hose and diaphram does not leak,,

[asaph]

The bake pedal goes all the way to the floor after the engine is started. It is hard before startup.

the booster may well be leaking all though I cannot tell for sure. It does make the idle rough any time the brake is engaged.

[Honda-Master]

you got a leaking brake booster...........as for the pedals going to the floor does it go to floor anytime u are at a stop?? if so u got a bad master cylinder as well...,,,,,,,, you can get reman booster at the DEADZONE ( autozone ) , checker

[asaph]

Well I feel stupid.

Sometimes a cigar is just a cigar....

I just got back from the mechanic that the car got towed to and it is a brake problem.

The rear brakes are blown out. The pistons were leaking and so when I added more compression due to the repaired head, it just forced it to blow brake fluid out onto the brake shoes even more. The problem was probably there before, and I did not know. Anyway, I feel silly after looking for a problem that was more complex than it just being brakes.

Wierd coincidence. Thanks for everyone's help. I will be taking advantage of all the info to tune the carb up. The tech said it needs a complete adjustment, (running rich now) more than I can pay him for at this time. From what I have found on the forum I should be able to step my way through it.
I am really glad I found this forum
Thanks again for all your help!