need help

[carauto]

93 volvo 850 new cat ,new o2 sensor new plugs egr ok no codes (no) is high 1600 at 15 mph and 1400 at 25mph (hc) ok and (co's) ok also

 

[PlasmaBomb]

So what's the question?

What is causing high NOx readings?

 

[exdeath]

Have the EGR system checked out. What part of it is "ok" ? It's easily possible for the valve itself to be perfectly fine, but have a bad vacuum line or something that prevents it from opening. 93 is pre OBD II it's not likely to have a flow sensor required for EGR self diagnostic (eg no codes or lights).

 

[exdeath]

So what's the question?

High NO and failing emissions apparently.

 

[carauto]

yes fail smog all parts of egr ok only (no) high

 

[exdeath]

Please elaborate and be specific on "egr ok", what was checked and how was it checked and what are "all parts"?

Check engine temp and look for lean mixture also.

NOx is easy, it's caused by high combustion temps, and there are less than a handful of causes.

 

[carauto]

egr was check with vac pump and opens and closees on volvo has a vac trans ducer electonic part was replaced alwing vac to work

 

[5150MyU]

Clogged EGR passage possible and as exdeath said lean.

 

[5150MyU]

There is also an EGR solenoid somewhere around the radiator shroud which I assume is what you had replaced -check the vacuum lines, also a bad coolant temp. sensor could cause the EGR to be omitted from the picture-just offering suggestions.

 

[PlasmaBomb]

High NO and failing emissions apparently.

Yeah got that after another read through... It was really late...

If your CO and HC are low there is the possibility it is running lean.

There is also the possibility that the EGR is working but needs cleaned (if it hasn't been inspected).

What is the fuel economy like?

Isn't your car is too old for OBDII codes... (again I don't know how extensive OBDI was). So if someone just told you the EGR wasn't throwing codes it's not worth much...

Finally was the car sufficiently warmed up before testing? The cats work best when hot. You say they are new, so they should be working...

1600 ppm NOx seems really high... but then I'm not use to '90s cars...

 

[PlasmaBomb]

Parts of the emission system for the Volvo 850