Pony 5.0

I just got my digital code reader from Amazon today and put it to use. I got a code 91, System always lean. I also found the vacuum line to the A/C broken. Is it possible for that small of a leak to cause a lean condition?

HACKGT350

yup any small lean can pull a code. try running the car and taking carb cleaner spray it around the engine on all the vacuum lines and along the gaskets of the upper and lower intake, if the idle goes weird you have found your leak

Texas5.0

I have the same code and have been told by several people on this site way smarter than me that code 91 probably means you 02 sensors are bad. Have you run both the KOEO and KOER tests with the 91 code showing?

Pony 5.0

I only ran the KOEO to pull codes since I have been getting an intermittent CEL. I just reset the computer and blocked off the vacuum line. I'll see tomrrow how my pony gallops and run the KOER. Thanks for your help.

JZTRK

REPLACE YOUR 02 SENSORS AND CLEAR YOUR CODES AND IT WONT COME BACK IT WORKED FOR ME 90 5.0 LX 5SPD

1991LX5.0

I know for a fact the its the O2 sensor because i just pulled my codes today and i got that code and another O2 sensor code. Looks like when i did my TKO swap i dented the side of my O2 sensor in so I know thats the cause

Pony 5.0

You were right! I fixed the the vacuum leak, reset the computer and rode my pony hard today. The code 91 did not show up; however a new stored code popped up: code 34 EGR not opening. I have an EGR delete plug in module that is supposed to keep the CEL from coming on. Will it still trigger a code anyway?