MadVladCivic

Greetings.

96 Civic DX w/ 111K miles. Passed Maryland emissions inspection on
July 14. Spark plugs (NGKs) replaced last November (less than 3k miles).
Car fires right up at start and is quiet and smooth. CEL has never been
illuminated. Car does not run rough or jerky. Acceleration is ok but it could be better. New fuel filter installed in June along w/ fuel pressure gauge.
Oil changes every 3k+ mi or 6months or so. New air filter.

Issue: An intermittent situation. Actually noticed this for the first time when
I was parked w/ the engine running after a short drive. While in Park mode,
the engine was surging. Subsequently, I see it when coming to a stop (stop light or sign), the engine appears to be racing/surging. It does not drop down into the gentle idle RPMs. The onset appears to be random and it disappears as suddenly as it onsets. When it onsets, the car seems to want to drive thru the brakes even as the braking to the point of stopping the car is completely normal. Flushed the brake fluid in June as I thought it might be fluid fade. Inspected and lubed the brakes as well. When the car is in this surge mode, the brake pedal will slip little by little towards the floor. Shifting the car into neutral while it is stopped and re-applying the brake demonstrates a normal brake pedal, eg, no sinking. When the surge disappears, the brake pedal is completely normal. The a/c seems to play a role but it is not 100% correlated. Switching the engine off also seems to
offer a re-set of the condition.

Throttle body need a good cleaning? IACV need cleaning? MC in early stages of failure? No FITV on the 96s.

Thanks.

ohsnapzafingcu

iTrader: (2)

If the pedal is slowly sinking to the floor it sounds like a brake master cylinder issue with the internal seals leaking. When you flushed the fluid do you recall how dirty the fluid was?

MadVladCivic

The fluid was only about a year old. I had seen the fluid fade issue before
in traffic on the Capital beltway in July 2-3yrs ago. It behaved much the
same way. Thought it might have returned per the description of my wife
so I flushed again. It wasn't that dirty. It passed the brake tests per the
service manny as well.

If it is the MC, shouldn't the pedal sink consistently and not just
at a few stop lights and then back to normal for days at a time?

mk378

Pedal sinking to the floor and failing to hold still is either a bad MC or a fluid leak. If you aren't losing fluid, replace MC. And yes if the seals are bad they may grab sometimes and leak other times. It will eventually get worse until it won't brake at any time.

A blown diaphragm in the brake booster will make the engine race when you step on the brakes (anything letting extra air into the intake on these MAP-controlled systems will cause idle to increase). If the booster is blown there will also be no power brakes but you may have gotten used to that.

MadVladCivic

If the diaphragm is problematic, shouldn't the engine race EVERY time
the brakes are applied; not intermittently?

No brake fluid leak. Passes the engine-off brake booster test per the
service manual among the other tests as well.

MadVladCivic

OK. Updated corroborative info.

Applied the Brake Booster Inspection tests from Civic service manny.

Functional tests #1 & #3.
Leak tests #1 & #2.

Passed all tests. Pedal level held constant for functional tests
#1 and #3 and for leak test #1. For Leak test #2, pedal started off
w/ give but firmed w/ successive pedal pumps.

These results duplicate the results from these same tests conducted
weeks ago.

So, if I took the car to a mechanic complaining of the situation described
in the initial post, the mechanic would also conduct these tests, yes?
Before indiscriminately replacing stuff.

Former User

Not if the mechanic is any good at his profession. Your symptoms are inconsistent with a brake booster issue.

Save some cash and replace the brake MC yourself and then bleed all 4 wheels until the fluid runs clear and no bubbles are released.

MadVladCivic

I was wondering when you were gonna show up!

I agree. It is likely NOT a brake booster issue. Basically, what I was getting
at w/ my comment that you quoted was that a mechanic would apply the
same tests out of the Honda manual that I did--getting the same results.
Are there other diagnostic tests for an MC given that I could not reproduce
the sinking pedal in the two tests (Functional tests 1 & 3), which seem to describe a diagnostic for the MC?

What size pushrod is indicated? The 13/16 inch?

Thanks.

Former User

Listen to mk. If there is no fluid leak and system is properly bled, the next logical step is to replace the MC. That's what a good mechanic would do without hesitation. Buy the MC for your car from Honda.

MadVladCivic

BTW, assume I take the car to a mechanic and explain the situation as I have in this thread. He a) decides to run the same tests as I have run and finding the same results that I have found, he b)takes the car for a test drive.
Assuming he cannot reproduce the pedal response as it is intermittent,
what does he do? Tell me he could find nada wrong or replace the MC
based solely on my description?

Former User

Replacing the MC is the next logical step, so he should do that based on your description of the problem.

Buy the Honda MC and hand it to the mechanic when you bring him the car.