Hello,

I failed the Low Speed RPM test on my 83 280ZX, 5-speed, N/A, with 120,000 miles.

Here's the Low Speed numbers:
HC - Reading = 198, Limit = 220 ----> OK
CO - Reading = 1.49, Limit = 1.20 ----> Fail
CO2 - Reading = 14.2, No Limit on the form
O2 - Reading = 0.03, No Limit on the form

Here's the High Speed RPM numbers:
HC - Reading = 49, Limit = 220 -----> OK
CO - Reading = 0.31, Limit = 1.20 -----> OK
CO2 - Reading = 14.7, No Limit on the form
O2 - Reading = 0.41, No Limit on the form

Any help would be much appreciated. Thanks...Robert

 

What's the timing set to?

Do you have a cat installed?

Have you checked the oil / plugs / plug wires / cap & rotor / sensor wires?

 

It hasn't had a tune-up in quite awhile, sounds like that's the place to start. Cat is in place, replaced the muffler a couple of years ago.

Thanks...Robert

 

What's the timing set to?

 

Not sure, haven't checked it in ages. What do you suggest?

 

Check the timing (with the vac advance on the distributor unplugged). Stock timing should be @ about 8 degrees. It will put out better emissions @ 3-4 degrees (but no power at all). Set it before taking it to the shop, then reset it after you get it back from the shop.

Also make sure the plugs are clean & have proper gap... an oil change sometimes helps (if the oil is really dirty & old). Also check vacuum lines (vac leaks can throw off emissions). Just a classic tune up & setting the timing will help.


OH... and check the O2 sensor (if it's the orig, it's probably time to replace it).

 

Thanks alot