Air/fuel running lean..... no temp sender hooked up.

[RFMustangGT]

Quick question guys. Can the temp. sender not being hooked up cause the car to run lean? I put an aftermarket sending unit in and never put the factory one in another spot. Just a thought that came across my mind while trying to resurrect this thing from storage. BTW, it did the same thing before it went into storage so I dont think it's from sitting over a year. Thanks!

 

[toyman]

Are you referring to the gauge sending unit or the ECT sensor for the PCM? The one for the gauge has no affect. The ECT sensor, depending on how the PCM interprets the loss of signal, will have a big affect. If the PCM sees that as a cold condition extra fuel will be added giving a rich mixture and a lean condition if it sees the loss of signal as being hot. My guess is the default is rich to protect the engine. IIRC the ECT sensor is the 3rd most important sensor used by the PCM.

 

[RFMustangGT]

yeah it's the gauge sending unit. Guess I need to look elsewhere. What the car does is when you are not rolling in the throttle (ie just holding constant speed) you can feel the car hold back as if you had your foot off the gas and the car was trying to cut back fuel to slow it down. It used to run rich all the time but now it's shifted to running lean. I guess maybe I have a vacuum leak or maybe an O2 sensor?

 

[HISSIN50]

What codes are you seeing?
Do you have a WB?

 

[RFMustangGT]

codes that it is pulling are 511 PCM ROM, 172 HO2S System Lean Bank 1, and 176 HO2S System Lean Bank 2.

 

[toyman]

Check fuel pressure and replace filter if you don't know when it was last changed and clean the MAF sensor.