msmith65
Well-Known Member
- Joined
- August 18, 2004
- Messages
- 345
- Reaction score
- 0
- City, State
- Dallas
- Year, Model & Trim Level
- '93 XLT
My '93 4.0 won't pass inpection. Too much NOx, over 1100 where 905 is the spec.
It's had some overheating troubles this year, at idle with the AC on, so I can see where too-high combustion temp could be the cause.
However, I don't see an EGR -- the likely source -- on this vehicle. In combing the archives here at the forum, I found some opinions that EGR wasn't installed on non-CA vehicles until midway through the 93 year model -- same time as the switch from R-12 to R-134a. This was definitely an R-12 vehicle.
With no EGR and no OBD codes flashing, what should I look for?
The generic form from the inspection lists:
Again, no codes. I did have a bout of acceleration ping last summer, which I traced to an intake leak (near the MAF sensor, which I cleaned) and fixed.
It's had some overheating troubles this year, at idle with the AC on, so I can see where too-high combustion temp could be the cause.
However, I don't see an EGR -- the likely source -- on this vehicle. In combing the archives here at the forum, I found some opinions that EGR wasn't installed on non-CA vehicles until midway through the 93 year model -- same time as the switch from R-12 to R-134a. This was definitely an R-12 vehicle.
With no EGR and no OBD codes flashing, what should I look for?
The generic form from the inspection lists:
- 02 sensor
- EGR
- ignition timing
- feedback sensor failure
- vacuum lines
- catalytic converter
Again, no codes. I did have a bout of acceleration ping last summer, which I traced to an intake leak (near the MAF sensor, which I cleaned) and fixed.