Thanks, Geoff. Check engine light is not lit, but I'll check for codes anyway.
In case I didn't already mention on this forum, I have replaced the EGR valve
and the camshaft sensor which were both throwing codes within the past year.
I'm not quite sure how you'd use the unlit blowtorch. I'm assuming you do
this with the engine running. What will happen if a vacuum leak is detected?
Thanks again.
John
Geoff <[EMAIL PROTECTED]> wrote:
Note: I thought I sent this out days ago, but it turned up in my
drafts
folder this morning. Sorry for the delay!
This requires some detective work. Typically this situation is caused by a
poor fuel-air mixture, which has a number of potential causes.
There are several factors that could be implicated:
o The cold engine is getting too much air. Possible vacuum leak; possible
stuck idle air control valve in throttle body.
o The cold engine is getting poor sensor data. Possible throttle position
sensor issue, also (remotely) possible O2 sensor issue
First thing to do is to check for trouble codes in the PCM. You can use the
key on-off-on-off-on method to see if any trouble codes blink out via the
check engine light. If you get something other than codes 12 and 55, report
them back here and it will help us to diagnose it.
If you don't have trouble codes, check for vacuum leaks using an unlit
propane blowtorch. Pass the nozzle of the torch around the areas where the
intake manifold mates to the top of the engine. Also check over any vacuum
lines you find, including the ones that lead to the evap charcoal
cannister. Make sure the fuel cap is secure.
Also check the condition of the throttle body. Is the butterfly gummed up,
causing it to stick partly open? If you see a lot of soot and varnish,
there's a good chance the idle air control motor is gummed up and sticking.
You'll have to remove the throttle body and clean it thoroughly using Gumout
and q-tips. Clean the idle air passage especially well. Avoid getting the
solvent on the throttle position sensor.
You can check the operation of the O2 sensor using a digital voltmeter.
Acceptable values are usually between 0 and 1v; when the engine warms up it
will cycle between those two values. An excellent description of O2 sensor
operation can be found at http://www.mr2.com/TEXT/O2_Sensor.html.
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