Hesitation

My 95 Civic with the 1.6 VTEC engine (195,000 miles)has been experiencing
some intermittent hesitation. This is most noticable on warm days. It
seems to have started about the same time as the change in fuel that now
includes alcohol. About the same time I had also checked and cleaned a
well operating PCV valve.
I have no ECU codes. The idle speed sometimes drops a bit when the engine
is very warm. The plugs, dist cap and rotor are almost new, The fuel
filter is going to be changed again. I have reviewed many ideas on the
search feature. I'm not sure if this car has an EGR system of some sort?
My manual only makes reference to the 1.5 engine having an EGR system.
Thanks in advance for any ideas or assistance.

 

I assume the new plugs, cap and rotor are OEM?

 

Yes, OEM. I should also comment that I noticed the
PCV hoses were a bit brittle and I used some soft Permatex to ensure a
good seal after cleaning the valve. I'm planing on replacing the upper
and lower PCV hoses as well as the valve. Prior to sealing the PCV hoses,
the hesitation seemed to be worse.

 

Random hesitation on an old car is usually caused by a failing oxygen
sensor. It becomes covered by molten ash with age. Eventually it's too
slow for the emissions feedback loop so you'll get surging.

 

Do check the level in the cooling system reservoir; top off
per the manual; purge of air. Forty minutes may be required
before the fan comes on twice during the purge procedure.
(Have you had any work done on the cooling system recently?)
Temperature sensors, inter alia, not fully submerged in
coolant will send erroneous signals to the computer, etc.

The oxygen sensor should be eliminated as a cause of this.
The 92-95 Civics, for one, are supposed to set a code for
it. Still, I'd keep it in mind.

After 1992, only the Civic VX came with an EGR system,
according to my Chilton's manual.

Air filter has been changed recently, right?

 

Oxygen sensor was replaced around 6 months ago because of a bad heater.
Water pump, timing belt replaced a month before the problem started.
Timing is right on the money. Just filled up with premium and added some
fuel system cleaner (Chevron with Techron). I have also purged the
cooling system, but I will check it again. Thanks for all the ideas!

 

Is it OEM?

Was the purge done before or after the water pump change?

Just want to cover all bases.

 

Thanks Elle....Air filter has less than 10,000 miles and looks good.
Replaced fuel filter today. Some nasty looking muddy stuff came out the
gas tank side to my surprise. It had 50,000 miles on it. Did the 30 min
purge of the cooling system today with the nose of the car up on maint.
ramps. Tweaked the idle up 1/16 of a turn. I'm going to test drive it
now and see what happens. Thanks again to all for the ideas.

 

I'd be surprised, too.

Get some bad gas somewhere?

Are the fuel lines maybe clogged with corrosive debris?

Try not driving the car all the way until the fuel gage is
empty. It's said that the fuel pump picks up all the bottom
debris from the fuel tank this way and puts it into the fuel
system. Not good.

I'd also add a bottle of Chevron Techron (~$6 at Wal-Mart)
to a near empty tank, then fill.

Monitor this. Sure sounds like you are on the way to
identifying the exact problem (related to the gunk in the
fuel line).

 

The gunk came out of the fuel filter on the input side. Fuel line from the
tank was clean. The problem started occuring right after the big switch to
alcohol in the fuel about a month ago. Service stations had to get the
water and gunk sucked out of their tanks before the new fuel with alcohol
was added because that fuel would let the water at the bottom of the tank
mix with it. Looks like my fuel filter did its job and captured some of
that. Put some Chevron with Techron in my gas tank Saturday.
I'm hopful my hesitation problem is solved! Thanks again.