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what is it on firewall?

vaicase

vaicase

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Messages
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Location
morley michigan
I have a 95. I was wondering abobe the master cyl there is a black box. with plug in in it, and a place for what looks like an hose. However there is no hose on it. Also there is one on the engine. Can someone tell me ,what they do? The one on the firewall keeps coming unplugged. the clip is broke ,so i zip tied it yesterday. Thank you
 
thanks guys. now what is that? what does it do? does the truck need it. advantage to having it is what? thanks again. the reason i ask is i put a new pittman arm on and when i removed the steering box, or when i put it on i broke holder clip and it came off. last tuesday i pulled my big trailer 100 miles and then yesterday i noticed it fell off. now it did drive a little different ,,,i think. thank you
 
Crankme69 said:
The ecm uses that to correct the boost press for elevation. Easy fix plug in the connector and wrap a zip tie around it to hold/lock the connerctor in place, many of my locks are held like that on mine.
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LOL :hmmm: We call that Illinois Engineering! :laughing:
 
I did a little reserch. It seems this sensor on the f vin , trucks only reads at start up. I dont understand why though. Its something to do with altitude and boost. It sounds like to me it has something to do with the wastegate on the turbo. could be a little bit of though. thank you
 
vaicase said:
I did a little reserch. It seems this sensor on the f vin , trucks only reads at start up. I dont understand why though. Its something to do with altitude and boost. It sounds like to me it has something to do with the wastegate on the turbo. could be a little bit of though. thank you
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O nan OBD1 6.5(94-95), the barometric pressure sensor(firewall mounted one) is used at all times to correct boost pressures based on elevation. At sea level a 6.5 will hold roughly 7 pounds of boost sustained, but at around 17,000 feet of elevation it will hold about 14.7 pounds of boost to keep the same volume of air inside the combustion chamber as sea level. With it unhooked I believe the ECM will default to sea level and set a code which could give you reduced engine power. Like above posters said, zip tie the plug up to hold it in place and go.
 
well, need to hook mine back up then! my 95 still runs pretty good though.

will a chip bypass this? I am not entirely sure mine hasnt been chipped, as it runs pretty hot power wise compared to the others.
 
In OBD1, since it was also a vacuum sensor, it could only read BARO at certain times, L65 or "F" VIN vehicles didnt check for vacuum like the EGR equipped trucks. As you gain in elevation, the atomoshperic pressure goes down, so boost is relative to a changing variable. The PCM uses that to know how much boost over atmospheric you have. To the engine and MAP, boost is a mass flow increase, more boost more mass, passing the same volume through the engine. Since the air is less dense as elevation increases, it may try to compensate with a couple PSI more boost. To the engine, more boost isnt more stress, because its the same total pressure as at sea level, just that atmospheric was greater and boost less.
 
btfarm said:
Thinking the same... as well as the driver and passengers turning blue from lack of oxygen...:hihi:

Would be one whale of a smoke show based on what I've done at 8,500 ft in the past. :eek:
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I've only had mine up to about 6100, but it didn't hardly smoke at all up at that altitude. Then again EFILIVE is pretty tuneable:hihi:.
 
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