what is this?
10-04-2005, 06:07 PM
#1
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Car: 87 firebird,89 formula,74 Olds that runs 12.34
Engine: LG4,L98,455Olds
Transmission: 7004r,7004r,th350
what is this?
I have two pics of two different sensors. What is what and do they both need manifold vacuum to work?
http://www.cardomain.com/ride/2136219/1
http://www.cardomain.com/ride/2136219/1
10-04-2005, 06:13 PM
#2
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Car: 81 Corvette
Engine: 355, ported vortec heads
Transmission: 700r4
The first pic I'm not sure what it did. I know the plastic vac line broke on mine and it didn't care. Sorry, I know that isn't much help.
10-05-2005, 09:03 AM
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Car: 89 Formula Firebird
Engine: 305 - Demon 525
Transmission: 700R4
The 2nt pic or the bottom on looks like a relay.If I'm not mistaken it has one thick red wire that goe directly to the eletric fan. If you can track down that in the haynes I'm sure you will find the name of it.
10-05-2005, 09:23 AM
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Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
The one with the blue plug is the baro sensor; the other one, with the vacuum line, is the MAP sensor.
The baro sensor DOES NOT get vacuum. Only the MAP. Somebody that didn't know what they were doing, added that extra vacuum line.
To get a "vacuum" reading accurately ("vacuum" being the difference between inside the manifold and outside it), compensated for altitude and so forth, the ECM needs to know both the pressure inside the manifold (MAP) and outside (baro).
Get rid of the rubber line that doesn't belong, and the car will probably run better.
The baro sensor DOES NOT get vacuum. Only the MAP. Somebody that didn't know what they were doing, added that extra vacuum line.
To get a "vacuum" reading accurately ("vacuum" being the difference between inside the manifold and outside it), compensated for altitude and so forth, the ECM needs to know both the pressure inside the manifold (MAP) and outside (baro).
Get rid of the rubber line that doesn't belong, and the car will probably run better.
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10-05-2005, 10:00 AM
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Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Alot of cars don't, and do.
It's also a safe bet that if your car doesn't have the baro sensor, the ECM isn't running code to use its signal.
However, if the RCM is looking for a baro, and it sees something else, weird things are bound to happen.
It's also a safe bet that if your car doesn't have the baro sensor, the ECM isn't running code to use its signal.
However, if the RCM is looking for a baro, and it sees something else, weird things are bound to happen.
10-05-2005, 10:12 AM
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Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Is this a ccc-qjet? There will be two pressure sensors, one on each side of the firewall. They are essentially identical except one is connected to manifold vaccuum and the other isn't. The computer takes a reading from the sensor without the vaccuum connection for a baseline air pressure reading. This allows it to correct for changes in altitude.
TBI/TPI may be similar but I have limited experience.
Sofakingdom said the same thing. He just posted before me.
TBI/TPI may be similar but I have limited experience.
Sofakingdom said the same thing. He just posted before me.
Last edited by naf; 10-05-2005 at 10:14 AM.
10-05-2005, 06:59 PM
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Car: 87 firebird,89 formula,74 Olds that runs 12.34
Engine: LG4,L98,455Olds
Transmission: 7004r,7004r,th350
Thanks for the replys. Yes this is on a CCC carb LG4. I bought this car from an idiot and I had to undo alot of things he did. After I did the car ran great but now I am chasing a bogging problem and cant figure it out. Although today I think I may have found the problem. I did a vacuum test on the engine and it indicates I have a clogged exhaust. The kid I bought it from said he gutted the Cat but I have not verified this.
10-05-2005, 10:14 PM
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Car: 1989 Iroc-Z
Engine: 5.7L TPI
Transmission: 700R4
Since his car has the LG4 carburated engine in it, picture #1 is the "BAROMETRIC PRESSURE SENSOR" and picture #2 is the "DIFFERENTIAL PRESSURE (VAC) SENSOR", They both serve a similar function