Each case could be different, but here's the latest on mine:
The diagnostic codes logged when the check engine light came on were
for ramdom misfires and misfire on cyl. 5. Both occurred at about 70
mph under a moderate load, which matches the codes logged from the
prior incidents. Cyl. 5 already had a new plug and plug wire, and a
new ignition coil pack was installed in February, so the FLVWD had to
dig deeper. After a few hours of testing and tinkering, the problem
was diagnosed as a dirty throttle body (caked with carbon), which was
impairing the function of the throttle control module. Diagnostics
also showed wide fluctuations in the mass air flow, which are
supposed to be relatively steady. The throttle control module will
usually "actuate" on command during a diagnostic test, but mine
wouldn't. After cleaning out the carbon and checking all
connections, the actuation worked, the mass air flow stabilized to
normal levels, and the idle seems smoother than before, even though
it wasn't too bad before. They added a can of BG44K fuel additive
for more cleaning. According to the tech, problems with the throttle
control module can manifest themselves in various intermittent
electronic glitches, from misfires to no A/C to hard starting, etc.
He also checked the EGR valve and it operated normally.
Does this diagnosis solve the problem? Time will tell, and I'll post
to the list if it recurs. Meanwhile, I'm interested in what the
others find out about their coughs.
Could this be what is afflicting the others? Tough to say. I've got
35k miles. However, I use mid-grade unleaded gas with detergent
additives, usually from Conoco or Texaco, I add a bottle of fuel
system cleaner a few times a year, and I get service at the suggested
intervals (including the major 30k service 6 months ago), so I didn't
expect the throttle to be dirty. Neither did the FLVWD apparently,
since this was the third trip to the shop for the same problem, and
this wasn't checked before. 3k or 4k miles for you other coughers
might seem to be too soon, but it is at least possible that a problem
could arise in so few miles.
Finally, to make good on my pledge to report good service as well as
bad: Ed Carroll Motors in Fort Collins charged only $17.50 labor for
the diagnostics and cleaning the throttle. Granted, my EVC was in
for its third visit since January for the same problem, but I was
expecting a MUCH bigger bill under the circumstances.
Joel Funk
97 EVC
