performance issue
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performance issue
Am I missing something? My 91 Ranger 3.0 refuses to let me navigate the mountains out east without having to downshift to 2nd. at times. What compensates for baromtetric pressure at altitude? Any ideas will be appreciated. Thanx
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
Not sure if your '91 uses a BARO sensor. Do you have something mounted up on the firewall that looks like this?
If so, that is the primary input to the computer regarding barometric pressure.
If your '91 does not have a BARO sensor, then it's primarily up to the MAF to provide feedback to the PCM so it can make corrections based on altitude (without a BARO sensor, the PCM infers BARO based on the MAF signal and some other sensor input).
In any case, cleaning the MAF sensor sounds like a prudent move:
https://www.ford-trucks.com/forums/s...hreadid=126093
If so, that is the primary input to the computer regarding barometric pressure.
If your '91 does not have a BARO sensor, then it's primarily up to the MAF to provide feedback to the PCM so it can make corrections based on altitude (without a BARO sensor, the PCM infers BARO based on the MAF signal and some other sensor input).
In any case, cleaning the MAF sensor sounds like a prudent move:
https://www.ford-trucks.com/forums/s...hreadid=126093
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
Ken, my SHO has an MAF and a BARO (BP) sensor, looks just like the one in the pic, and it's mounted on the firewall. And I'm pretty sure the 3.8L T-Bird SC also has both a BARO sensor and an MAF. That's why I'm not really sure which years/models/engines would have the same setup...
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
Me too, until I bought the SHO. 
I'm trying to think why the DOHC Yamaha 3.0L and the Ford 3.8L SC would have the BP sensor in additional to the MAF. Both engines really have very little in common, except that they both are higher compression designs. I'm wondering if that is the reason (or one of the reasons) why barometric pressure must be more accurately measured and reported back to the PCM, as opposed to the PCM simply making inferences based on other data.
I'm trying to think why the DOHC Yamaha 3.0L and the Ford 3.8L SC would have the BP sensor in additional to the MAF. Both engines really have very little in common, except that they both are higher compression designs. I'm wondering if that is the reason (or one of the reasons) why barometric pressure must be more accurately measured and reported back to the PCM, as opposed to the PCM simply making inferences based on other data.
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