CRX HF weird stuttering problem

I have an '88 CRX HF with 175,000 miles on it. The engine shudders
pretty violently when the accelerator pedal is held at a particular
spot in its range of travel. It occurs in any gear, at any RPM. It is
more noticeable at lower RPMs probably due to the lower inertia of the
reciprocating mass. If I press the pedal down past this point, say
~1cm, it goes away. Similarly, if I let up on the pedal the same
distance, the shaking also stops.

Car has new plug wires, new O2 sensor (Bosch), new distributor, and a
MotorVac flush service done. Its also had a new timing belt put in and
a valve adjustment done in the past 25k.I suspect it could be the
throttle position sensor, but I'm not familiar with its construction.
Is it possible that it could have worn out in this spot and is sending
bad/no signals? Any other ideas?

On a related or unrelated note, the car also idles erratically,
sometimes too high (1100RPM), sometimes too low (250RPM), sometimes it
bounces between 900-1100RPM. A Honda tech told me my accelerator cable
was too tight. I haven't fooled with that yet.

 

I think that's your problem there. Dump that crappy Bosch O2 sensor and get
an OEM unit.

 

first things first: check the ecu for error codes. go to tegger.com to
see how it's done. report beck accordingly.

 

Non-OEM O2 sensors being behind poor performance has come up
here before. I echo Misfit's suggestion.
https://www.automedicsupply.com/ has OEM ones for about $35
total for your 88 CRX. I bought a new OEM O2 sensor here a
few years ago for my 91 Civic. No problems in the
transaction. Works great.

Also, thoroughly purge the cooling system of air. Various
idle control components are cooled by it. Air in it will
cause sub-optimal idling, among other things. Make sure the
fan comes on twice during the purge process. From cold
engine to fan coming on twice may take over 40 minutes. It
does on my 91 Civic.

 

I placed an order for the OEM sensor, and downloaded the PDF for
checking the codes. How do I go about purging the cooling system of
air? I'll post results when I get them.

On a side note, does 43-44mpg sound about right for an '88 w/175k?

 

A factory service manual for your 88 CRX is free online at
http://www.honda.co.uk/car/owner/workshop.html . See the
procedure for purging (= bleeding) under Engine, Radiator.

fueleconomy.gov reports that the 1988 CRX HF should get at
least 45 mpg in the city and at least 53 mpg highway. That
might be worth nothing. There are some online CRX groups
that you might ask. The Usenet archives (groups.googling for
88 CRX mpg) turns up a wide range, with yours appearing to
be about in the middle.

My 91 Civic has 176k miles on it. Fueleconomy.gov reports
31/35 city/highway. Yet it averages about 40 mpg year-round.
From online reports of other c. 91 Civic owners, that's
pretty usual for a properly maintained one.

Your engine has the same displacement as mine (1.5 L) but
yours is MPFI (mine is DPFI) and 8-valve SOHC (mine is 16).
Also, I suppose your CRX is notably lighter in weight.

Some fuel economy-oriented maintenance tips:
http://home.earthlink.net/~honda.lioness/id11.html

If the car has never had its PCV valve replaced, I'd do
that, first. I replaced my 91 Civic's at 138k miles, and
this made a huge difference in gas mileage, like 10% or so.
The valve was badly fouled with waxy buildup.

 

Replaced the O2 sensor today with Denso OEM from automedic. Took a
short drive in rush hour and I believe this solved the problem.

I heard that it is good to clear the ECU of codes when you install a
new sensor. Is this true? If so, I heard the radio needs a security
code to function again if the battery is disconnected long enough to
clear the ECU. Anyone know where to find the code?

Thanks for all the help. This is my first Honda, and it's comforting to
know there is such great support online. : )

 

Actually, unfortunately, the problem is still happening, to a lesser
degree. I can't find the stutter until I am in fourth or fifth gear,
and really looking for it, but it's still there. So I guess I'll reset
the ECU when I can, and try the other procedures listed in the
thread....dang.

 

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If it had a Throttle Position Sensor in it, I'd vote for that, but it's
too old for that, right?

'Curly'

 

curly, the o.p. /still/ hasn't bothered to check for codes afaict. in
my experience, tps problems /definitely/ show on the ecu.

 

I have a 90 Model Crx DX and my car is doing the same thing. If you
finally figure out how to fix it, PLEASE, share the info with me. We
have tried everything but a new computer.

 

Not sure, but I'd check the entire fuel system: tank, pump, filter,
injectors, and fuel lines.