Are you sure you have an air pump in your 94? I thought they got rid
of those stupid smog pumps with the magnum engines.
How close do you live to your testing station? How long did the truck
sit, not running, before it was started and run on the dyno? For my
last emissions test (before my engine swap... and coincidentally while
I still had a smog pump) I took the truck to a chain muffler shop
twice, failing both times, just over the limit on hydrocarbons. I
replaced things like the O2 sensor and the air pump switch with no
significant improvement. So I tried a different place... a smaller
shop with much friendlier service. Here's the difference between the
two shops:
chain shop
I drove 5 minutes from work to local chain shop, shut it off. It sat
10 minutes before they drove it onto the dyno and shut it off.
Strapped it up, set up sniffers, twidled thumbs, booted computer... 20
minutes later, started truck. Ran tests quickly, returned truck to lot
with failing marks.
small shop
I drove 20 minutes to smaller shop, shut it off. It sat 10 minutes
before they drove it onto the dyno and shut it off. Strapped it up,
set up sniffers, started truck. *WHILE THE TRUCK RAN* they booted the
computer, and tended other customers and tasks for 10-20 minutes. Ran
tests noticeably longer than the chain shop, and returned it to the
lot with passing marks.
The key is testing the truck WARM. Any shop *should* know how
important that is and should make sure the truck is warm first.
Don in CT
89 DakVert with 94 5.2/5spd/4x4 which has not yet been emissions tested...
74 Dart Sport 340 emissions exempt :-D
On 9/27/07, rws <rwsam2002@yahoo.com> wrote:
>
> Hi,
>
> I took the '94 Dak 4x4AT 5.2L @ 162k mi. in for the CA Smog Test and it
> failed the 25mph test HC Passing is 50 and the Dak got 51, so it failed
> by one.
>
> Cat converter (Magnaflow P/N 94006) was replaced Aug 2004.
>
> O2 sensor, ECT coolant sensor recent replaced, Ign. Coil, TPS replaced
> 2 years ago.
>
> Magnaflow tech said to test Cat by Temp differential front and back of
> the Cat and it should be 50-100oF difference. Temp will be around
> 400-600oF, so I need to find a temp gage for that range and need to
> find.
>
> But in the meantime I am suspecting the Air Pump or the Air Switch
> Valve.
>
> How do I test Air Pump and Air Switch Valve components to make sure
> air injection system is operating correctly? What is vacuum
> measurement at the Air Switch Valve?
>
> Also I am wondering if it is not getting proper air injection will that
> alter the temperature difference test on the CAT?
>
> ref:
> 15 mph test HC 85 MAX 18AVG 85MEAS NOx 491MAX 149AVG 432MEAS %O2 0.1
> 25 mph test HC 50 MAX 12AVG 51MEAS NOx 744MAX 144AVG 296MEAS %O2 0.2
>
> Please need help soon.
>
> Ron
>
>
>
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This archive was generated by hypermail 2b29 : Tue Oct 02 2007 - 15:23:18 EDT