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86 honda accord dies when brakes applied


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02-17-02, 08:10 PM   #1  
fotopep
86 honda accord dies when brakes applied

My 86 Honda Accord (carbureted dx model) dies when the brakes are applied and won't let me set the idle speed below 1200 rpm's without dying. I've heard that this is indicative of a vacuum problem in that applying the brakes somehow changes vacuum pressure? Any suggestions on how to troubleshoot and correct?
Can't seem to figure it out using Haynes manual.
Thanks in advance.
more info:
I recently solved a fuel supply problem by replacing a faulty ignition coil that wasn't powering up fuel pump. Both fuel filters are new, and fuel pump is 2 yrs. old. Plugs are clean. Idles and accelerates fine till I touch the brakes, then rmp's take a dive--weird!

 
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02-17-02, 08:20 PM   #2  
Power brakes I assume...I think you'll find that your brake booster is bad. Probably a busted diaphragm inside it. I'm not very familiar with that car though.


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02-17-02, 08:22 PM   #3  
mooser1
the power brake booster on your car operates off of vacuum...it sounds as though your booster has gone south, in effect creating a giant vacuum leak, this is why you can't get it to idle below 1200...

check the large vacuum line running from your intake manifold to the booster unit, you may get lucky and just have a broken or loosened line...might have pictures of this line in your Hayne's manual...

 
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02-17-02, 09:42 PM   #4  
fotopep
thanks

thanks a million for the timely advice--I'll check it out tomorrow and post reply!

 
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02-18-02, 12:00 PM   #5  
Joe_F
I agree with both of these guys. Sounds like a wiped booster. Is the brake pedal hard?

 
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02-18-02, 12:28 PM   #6  
fotopep
thanks again joe

brake pedal is mostly spongy--not hard, but doesn't go anywhere near the floor either. Can't find the booster yet--Haynes manual says it's behind master cylinder, but I don't see a vacuum line connection there, and the manual doesn't diagram it out for me.
Also, I'm going to bleed the brakes to make sure there is no air in the lines. Even if that's part of the problem though, that doesn't explain the idle issue. Sounds like I'll need a new brake booster.

Also, anyone know where that pcv valve is located? I wanted to check it as well. But, once again Haynes stops short of diagraming it out.

And yes, I'm in the market for the factory manual as my honda problems have become too complex to be without one.

 
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02-18-02, 12:58 PM   #7  
mooser1
man, those Honda's are a vacuum line nightmare...

manual is right, the booster is behind the master cylinder, I mean right behind it, the master cylinder actually bolts to the front of the booster...should be a larger (1/2" - 5/8") line running to it.., check this line for breaks, might be the problem...

pcv valve is located in a larger line, same as above, coming out of the valve cover...

from what you describe about the brake pedal, I am beginning to think maybe another line is broken or loose somewhere and when you apply the brakes it takes all the available vacuum away from the rest of the system...there are a million vacuum lines on this thing along with several vacuum controlled valves...very carefully inspect each line under the hood, I'm almost certain you'll find some bad ones...check the largest first and work your way down to the smallest...

post back what you find, I'm curious...

 
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02-18-02, 01:46 PM   #8  
Joe_F
If there is a check valve from the line going to the booster to the intake/engine area (this is where it gets its vacuum) check that and the grommet for cracks or breaks. It will do the same thing as a bad booster. Shouldn't be more than a few dollars at the dealer or any parts store.

 
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02-18-02, 03:00 PM   #9  
mooser1
kinda hard to see in the pictures I looked at, but there seems to be a large diameter line coming out right at the back of the carb, I would suspect this one to be the booster line...

 
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02-18-02, 06:28 PM   #10  
mooser1
this picture will show you the elbow and the large vacuum line to it that should contain the PCV valve...


 
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02-18-02, 07:58 PM   #11  
fotopep
will do

thanks again guys! I'll follow your suggestions and let u know what I find. Especially kind of you to include the picture--that's where I expected to find the pcv valve, but on my honda that pictured vacuum hose goes from the valve cover to the side of the air filter where there is a small filter in a small box, but no sign of the pcv valve at either end or in-line? hmm, I'll look thoroughly tomorrow again. Appreciate your help.

 
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02-18-02, 08:59 PM   #12  
mooser1
darn, only pic I could find, took me about 2 hours to figure how to post it.....

Oh, well, it's the thought that counts...

 
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02-19-02, 03:37 AM   #13  
Joe_F
Look on your underhood vacuum diagram sticker. It should picture where the PCV valve is. Get the new one from the parts store and you'll know what you are looking for

 
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02-19-02, 01:22 PM   #14  
fotopep
here's what I've found so far

First, when carbureter cleaner is sprayed around manifold intake gasket, engine revs and bubbles are visible in two places.

Second, I found and tested break booster vacuum line. Clean with good suction. I also tested brake booster using Haynes 3 step test, and it passed all three. (pedal firms up progressively when pressed 3 times while engine running, stays firm with pressure for 30 seconds with engine off, and moves down slightly when engine turned on etc.) So does that indicate my booster is ok but just draws enough vacuum from an already leaking system that it forces a stall?

Third, found pcv valve in center and under air cleaner on U-shaped 4" vacuum line. When vacuum line closed with pliers, audible click heard from pcv valve. Thus it seems to be working. Also found one other small vacuum line with slight cracking and replaced. Thoroughly inspected and traced all of them.

So, anyone care to share my options for correcting the manifold gasket vacuum leak? And does that explain my fast 1200 rpm minimum idle? Is it possible that I can get away with tightening the four bolts holding the carb down on the gasket? Gasket looks clean, but leaking plenty it appears. Any idea how much it will cost for parts?
Thanks again in advance. Would love to get one more year out of this car as my finances are a bit compromised presently.

 
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02-19-02, 01:32 PM   #15  
Joe_F
If you spray cleaner and the idle goes up, you found your leak. Try tightening the bolts, but you probably need a new gasket for the carb. Shouldn't be more than a couple of bucks through a parts store or the dealer.

 
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02-19-02, 01:40 PM   #16  
mooser1
sounds like you're on the right track now...

brake booster is good according to Chilton's...

sounds like PCV is working ok, it's cheap to replace if in doubt...

yes, this does explain the 1200 rpm idle situation...

you're going to have to correct the intake gaskets for sure, don't know what they cost, you can try tightening the carb bolts but probably won't cure it, once they're that far gone it's time for replacement...

good job on finding the problems, glad to help...

 
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02-20-02, 08:51 AM   #17  
I would suggest to remove the hose that is closest to the intake manifold & plug it up. If it idles properly you found your problem. Your leak may lay on the vacuum hose going to the brake booster. I hope this helps. Keep us posted.

OM

 
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02-20-02, 09:35 AM   #18  
mooser1
man, otto, you're right on top of it.....

very timely advice.....

 
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02-20-02, 07:19 PM   #19  
fotopep
latest progress

refresher:86 Honda Accord DX 5-spd carbureted 2.0 160k miles 1-owner
thanks for your help!
Ok, today I tightened down the carb. and apparently eliminated the manifold gasket leak--no increase in rpm's when carb cleaner sprayed this time.
Now she'll idle for awhile about 1000 rpms as opposed to 1200. Below 1000, she starts to die and then something kicks in that takes her all the way to 1500 plus and then she backs down again.
Can't find anymore vacuum leaks--inspected the brake vacuum again and it looks good.
Tried pluggin a couple of hoses from the intake manifold with no noticeabe difference in idle stability.
Is there a vacuum controlled idle swith/solenoid/controller that I should test? Once again, Haynes doesn't get that specific, but in scanning other Honda posts, that seems like something I should test.
Also, is it possible I'm running lean in my gas/air mix? Again manual's generalized direction evidently don't apply to my model.
The vacuum/emission control/carbureter/idle speed complexity of this friggin beast is a nightmare. If we hadn't spent fourteen quality years together and I hadn't donated all my xtra money to corporate America via the stock market this year, she'd be retired. The reality though is that I need another 15 or 20k miles out of her if possible. Think I should pay a visit to the dealer? Perhaps their experience would streamline things in this case.
Also I've got a bid on ebay for the 1986 Honda Accord Factory Service Manual--should get it as I don't think there's too many other fools out there in my shoes.
Anyway, once again--any advice will be appreciated.

 
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02-20-02, 09:29 PM   #20  
Joe_F
The factory manuals are well worth it. Check for the price of a new one. Believe it or not, it might be CHEAPER than Ebay.

I don't bid on Ebay. I give the seller an offer he/she can't refuse. Most times if there are no bids, they contact me and I wind up with what I want .

Hold onto your shoes until you get it. Then try to tackle your vacuum problem using that as your guide.

Carburetor woes and troubles plague these when they get very old.

Drive it as is (if you can't rectify the vacuum leak) as an old Honda in need of repair will soak you fiercely. This is when these cars come unravelled...when they get old like this.

 
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02-20-02, 10:32 PM   #21  
Does it still die when you apply the brakes?


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God bless!

 
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02-21-02, 08:15 PM   #22  
fotopep
nope

No, doesn't still die when I apply brakes. But, rpms drop somewhat sometimes. Brake booster still suspect in that brake is not consistently totally firm--even after bleeding yesterday.
Bought a fuel pressure/vacuum gauge today and discovered fuel pump is pushing 2.o psi--should be 2.6 to 3.4 to be satisfactory according to Haynes. I checked it at the carburetor. Tomorrow I'm going to attach a small length of fuel hose to the fuel pump itself and measure pressure there, just to confirm that it's the fuel pump and not the line that is under spec. Also I'm going to try to pick up a used or otherwise cheap brake booster.
Think my problem is likely a combination of things. In spite of the frustration at times, I'm enjoying playing detective technician with you guys help. And if I can get the factory service manual, I'm sure that will help too. Any input still appreciated?
I have access to a u-pull-it junkyard that will allow me to replace parts cheap, and I can test most before buying. So I plan on working through this in a process of elimination in order to get another year out of the beast! Thanks for sharing!

 
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02-21-02, 08:20 PM   #23  
mooser1
hey, thumbs up ..... glad to help, keep us posted.....

 
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