1. Home
  2. Volkswagen, everything else
  3. '85 Jetta (Gas) fails NOx Emmissions inspection

'85 Jetta (Gas) fails NOx Emmissions inspection

Just took my '85 Jetta for the required Oregon emissions inspections - and it failed the NOx test with a measurement of 4.78 g/mi which is over the state limit of 3.70 g/mi.

My first thought was - a bad EGR valve. But it doesn't have an EGR valve. My second thought was maybe I had the wrong spark plugs or incorrect gap or bad timing, making the combustion temp "hotter". But my spark plugs are Bosch Platinum WR7DP with a gap of .032 and the timing is 6 BTDC, just as it should be.

Any ideas ???

The other emissions are well within spec - CO is 11.2 g/mi (Max=32.0), THC is 0.94 g/mi (Max=2.00)

Thanks in advance for any advice.

- FM -

Reply to
Fred Mau
Loading thread data ...

Hows the cat?

Reply to
Biz

read here, it is interesting :-)

formatting link

and here

formatting link
the potential causes of non-compliant NOx readings are:Misfire condition Malfunctioning or improperly adjusted EGR valve (N/A IN YOUR CASE) Failed oxygen sensor Leak in exhaust tubing upstream of converter Excessive carbon deposits in combustion chamber Improper spark advance Blocked coolant passage Overly lean air-fuel mixture Damaged cold air duct Corroded or damaged engine sensor electrical connections

Plugs could be Bosch WR7DCs or WR7DTCs(?) gapped at 0.028". Check the FI seals for leakage.

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

Reply to
dave

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.