96 ex stalling while idling

A friend of mine has a 96 ex and says when the engine is hot and he is
idling at a long traffic light sometimes the engine will just start idling
really rough and then stall out. He starts the car and it's ok. Sometimes
for the rest of the day. This happens more when it's hot. The car has
120K. No check engine light on and scanner shows no codes. What could be
causing this? Thanks Larry

 

There are several possibilities. The best place to start would be to do a
complete tune-up. If your friend does not know how to do it, he should
have his favorite local mechanic or the local Honda shop mechanics do it.

If he does not want to do that--tell him to go to a auto parts store like
Auto Zone and get a can of chemicals that he pours into a full tank. The
chemicals clean all items related to the fuel system--especially the
injectors that can easily get clogged and cause all sorts of problems.

 

If it comes down to blind shotgunning of parts, I would start with the "main
relay" for about $50 at NAPA. I'm not sure how hard it is to get to on the
'96 (it is about an hour's job on my daughter's '93), but it is notorious
enough for symptoms like this that it is a good suspect. The rough running
before stalling, then works okay when restarted is especially suspicious for
the main relay. In addition, lack of a "check engine" light suggests the
problem is one the ECU has no knowledge of - often something between the ECU
and the spark or between the ECU and the fuel spray. Fading away always
makes me think loss of fuel pressure (ignition failure is more often like
hitting a switch) and the immediate return of normal operation suggests the
fuel pump itself isn't dying. The main relay is cycled every time the car is
started, so it gets my "evil eye" award for this one. In addition, the age
of the car makes sense for the main relay.

I replaced the one in her '93 a couple weeks ago after resoldering it a few
months ago. I am a new convert to the "replace if possible, resolder if you
can't replace" crowd.

Mike