Bad Thermostat Causing Ignition Problems?

I have a 1993 Honda Civic that recently started displaying some weird
ignition related problems.

I noticed that sometimes the tach ocaissionally spikes during operation.
The car also started to run rough one day and proceeded to get worse. I
replaced the ignition module (the one in the distributor) and it fixed the
problem (temporarily). About a month later, same thing (replaced another
module). I have done this several times.

I noticed that the car is running cooler than usual, and suspect a bad
thermostat.

My question is:

Can a bad thermostat causing a low coolant temperature cause the kinds of
problems with the ignition I am decribing here? (Theroetically, the coolant
temperature switch doesn't get hot enough, maybe causing the ignition to
deliver too hot of a spark all the time, causing it to die prematurely?)

HELP!

 

I don't see a correlation between low engine temperature and ignition
problems. If the car is running cold all the time then depending on the
temperature this may cause things to act differently than they would at a
correct operating temperature.

As far as "hotness" of spark I don't believe the voltage/amperage is
variable as far as output goes. What determines the voltage/amperage at the
spark plug tip is fuel mixture, compression of air in cylinder, cap and
rotor condition, cable condition, plug gap etc. I believe when it is time
to fire a plug the ignition coil just unleashes whatever is needed up to its
design limits. If you have low compression, a rich fuel mixture and a small
plug gap then it would not take much energy to jump the gap of the plug. If
you have a big gap, lean fuel mixture and a highly compressed air space then
it would take more energy to jump the gap. The ignition coil/ignitor
wouldn't die prematurely without some inherent defect.

I am not sure about the Honda setup but the Ford ignition modules require
heat sink paste on them to help dissipate heat. If this isn't installed
correctly it will shortly overheat and cause problems like you have
described, eventually failing altogether.

If somebody in this group doesn't have an answer for you I would check with
the Honda service manual and possibly attempt to run some codes on the
problem.

CaptainKrunch

 

I don't believe that replacing the thermostat will have any effect on
problems related to the ignition module. There could be another problem
related to the electirical system that is causing the ignition module to
wear out so quickly. It's hard to guess as to what it might be. I suggest
that you do a complete tune-up. If you don't have the proper testing
equipment--I suggest that you have the tune-up done by your favorite
mechanic or at the local Honda dealership. The mechanic will hook it up to
a very expensive computerized testing instrument and may be able to
determine the source of your problem. You should tell the mechanic about
your specific problem prior to tune-up.

 

Coolant a quart low will make temperature appear to be
cooler as engine is overheating. Fuel injection system must
know correct engine temperature to properly adjust fuel
mixture. If engine temperature is hot and coolant appears
cooler, then FI system has been observed to cause a cool
engine to repeatedly surge and a warm engine to run rough -
both while in idle. Why? FI system is only responding
according to its inputs - because of a coolant shortage.

How do you know engine is cool? Only from temp gauge on
dash? Not good enough. What is the temperature of water by
actually measuring inside radiator. A difference can exist
between these two reading.

Why, for gads sakes, were you wildly replacing the ignition
module - and multiple times? If ignition module was bad, then
simple test equipment would have made that obvious up front
before wasting any money on new modules. If you don't
specifically know what the problem is, then first get a
responsible dealer or mechanic to, first, take some computer
readings. Bottom line - it will cost less. And demand that
printout so that you can also learn.

 

Loose distributor bearing (felt using fingers) may cause the sensors no
longer work properly. Because this signal must be consistent, missing a
signal or adding too many signals could cause a bad firing timing. Keep in
mind that this signal is again modified by the ECU. For example, an RPM
spiking is probaly an indication that a normal sqaure wave width has suddenly
shrunk then, afterwards, go back to normal. The technician scope can pick
this up.

I recommend looking at the distributor, ECU and it's pipeline. Replacing the
igniter is merely a patch to the real underlying problem. -The low temp is
just probably an open thermostat.
Indi

 

I would definitely have to disagree with your coolant being a quart low
theory.

True that if coolant is low on some cars there might be no water availabe at
the appropriate temp sensors and the engine may be hotter than the guage
states. It is also true that coolant temperature is an input as to the
parameters in which an engine operates. HOWEVER this is not going to cause
a fuel injected vehicle to surge or run rough. It makes no sense. When you
start your vehicle and it is cold it certainly doesn't run rough or surge
and if it is hot it doesn't run rough or surge. The coolant sensors would
not cause a fuel injection system to operate outside it's programmed
parameters and cause driveability problems as you have described.

CaptainKrunch

 

I too will have to disagree on that.

Not even. The sensor for the gauge on that car is on the thermostat
housing, low down on the engine block, so you will have to be seriously
low on coolant before the sensor will get dry. If it does go dry and the
engine overheats, the sensor will get hot as well, and you most
certainly will se the temp gauge heading north. If you burst a hose and
loose all your coolant you definitely will want the gauge to show you
that the engine is overheating, and this is exactly what it does.

 

It is just that only hours before, we solved the exact same
problem on a Toyota. We had just put one quart of coolant
into the Toyota whose sensors said the engine was running cool
- but the water in radiator was boiling - bubbling hot.
Refilling the cooling system solved a surging and unstable
idle, and increased heat to the heater core.

FI system needs the exact engine temperature to provide
proper operation. With low coolant, the FI system was not
functioning properly causing surging when cool and unstable
operation when engine was 'long term operation' warm.

Its only a theory for the Civic. It was reality for the
Toyota.

BTW, all Hondas have a bleed valve at top of engine so that
air pocket does not remain inside engine. If coolant is low,
then the air pocket should be bled at this valve.