CIS problems. High CO on emission test.

[Konstantine Bogach]

Can someone lend me good MAC-14 for a test?   I would drive couple hours to
do a quick swap and test.   I live around Princeton, NJ.

Konstantin.

Konstantine Bogach wrote:

> Hi.
> My time came to pay dues to CIS gremlins.    It started when I did not
> pass emission test - CO is 0.7 (whatever units they use) while limit is
> 0.5.
> I did not think much - changed wires and spark plugs - anywhay they were
> due to and I found that one wire was broken.   It did not pass test
> again.  The patient is 200tqa '89.
> Driving with duty cycle meter hooked up to CIS test connector I found
> that I can not fix the duty cycle.  At first look it turned out  to be
> 70% at idle,   I adjusted the screw to ~50% (engine is warm,  numbers
> are average values ).  Raise rpm several times,  checked - 50% at
> idle.   After driving several minutes  I noticed that idle duty cycle
> fell to ~30% at idle.   Adjusted again to 50%, drove several minutes -
> 70% at idle.  Again: it is all on warm engine.   I tested TPS - good,
> its wiring is good,  wiggling wires at connector did not changed .2 Ohm
> between TPS connector and ECU connector.  Checked air temp sensor - good
> (resistance ~500Ohm,  no broken wires observed,  wiggling test was
> passed).   No vacuum leaks.  By the way,  rubber cap from plumbing in
> Home Depot is like made for intake pipe.  Plug intake side and you can
> pressurize whole system except intake rubber boot over air flow
> meter.    So, I checked vacuum leaks - no leaks.
> Checked fuel system pressures - in spec.  Residual pressure holds very
> well which means injectors do not leak, right?   It also means that fuel
> pressure regulator do not leak as well, right?  So, I need to find
> another explanation for longer cranking if the engine is shut off for
> more than 30 min.
> This "binary" state when duty cycle rocks between ~30% and ~70% makes me
> think that ECU is faulty.   OXS is relativly new - 15-20 Kmi.  I looked
> at OXS signal on oscilloscope and it looked fine.
>
> My second 200tq '89 did not pass emission test with same results  -
> CO 0.7  but in this case duty cycle is stable on ~50%.   I did not look
> at this one yet.   It is just to add to drama :)
>
> I wonder what content of CO in the tail pipe other people have?
> Does anybody in central NJ of Phili area have gas analyser or can
> recommend a mechanic who knows CIS well and, preferably, will let me in
> the shop?
>
> I will appreciate your comments and advices.
> Thank you.
>
> Konstantin.
> Hightstown,  NJ.