timmy0tool

iTrader: (7)

just FYI upstream sensors do differ from downstream, in wiring and connection to the car.
to be expound further, upstream measures air/fuel while downstream measures cat efficiency.

are the cats you ordered factory replacements or will they need welding?

OMAHA

Eastern brand

OMAHA

replaced all parts, cats and sensors, fuel filter......STILL HEARING A MISS!! Mechanic looking at the possibility of a bad plug or wire. Wants to diagnose problem before putting new cap and rotor, plugs and wires on. ANY IDEAS!??

Nlewis

oldskewel

iTrader: (1)

here are my notes for my '91:
O2 sensors
Denso is OE, Walker is a decent alternative.
There are 4 total
2 "main" O2 sensors are Left and Right, pre-cat, identical, heated, 4-wire (blue, white, 2 blacks for the heater - polarity of those does not matter).
Denso OE is 234-4211
Denso universal is 234-4000
Walker universal is 250-24000

2 secondary O2 sensors are Left and Right, post-cat, identical, not heated, 2-wire. Only for emissions testing. Do not affect running. Only reason to change those is if I get a CEL telling me they're bad.
Denso OE is 234-2015
Denso universal is 234-2000
Walker universal is 250-22000

dveneman

If you still get a code after changing the O2 sensors, make sure there are no exhaust leaks anywhere .
A leak may be causing the system to signal a fault.