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Old 12-25-2005, 01:43 AM   #1
projectrally
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Join Date: Jan 2004
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Location: South Portland, Maine
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2007 Forester XT 5mt
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Default P1143?

Code=Pressure Sensor Circuit Low Input

I've got a 99RS. Checked here and RS25.com to find out what this means, exactly. I assume it's MAF related, but I can't be sure. Anyone want to help me out? At first, it was just this code, but the engine was running fine so I didn't worry about it. Then, the car started to behave strangely, like it wasn't receiving throttle inputs. The car would decelerate like I no longer had my foot on the gas. No throttle compensation would fix it. Then, all of a sudden, the throttle would be back and I would be driving fine again. Later, when I checked the codes again, I had thrown cylinder misfires on all 4 cylinders.
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Old 12-28-2005, 12:01 AM   #2
ase05scooby
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the maf sensor just reads the amount of airflow its not pressure related i have alldata at my job and ill check it in the morning and see if i can find anything to help you.As for the misfires it could be spark or compression or fuel related
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Old 12-28-2005, 07:13 PM   #3
ase05scooby
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P1143 description is intake manifold pressure sensor circuit range low. The sensor reads pressure and will affect fuel and air ratio to the engine its very possible for this to cause a misfire.Its usually located on the throttle boby check all your vaccum hoses and make sure none are cracked or disconnected.The most common cause of this problem is the sensor itself going bad try unpluging the sensor and starting your car if it changes anything its your sensor if there is not a change you have another problem. Try this and let me know how it goes.
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Old 12-28-2005, 07:48 PM   #4
ivwarrior
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I had this happen in my work van the other week. Poor running, wide open throttle and it was just slowing down. Then all of a sudden it would clear out and take off. Then the next day it would start and stall out. Couldn't keep it running. Dumped in 2 bottles (27 gallon gas tank) of dry gas and after about 15 more "start and stall out" events, it stays running. Filled up with fuel, drove a few miles and it cleared out completely. Haven't had a problem with it since.....

Cliff notes: Perhaps you have water in your gas tank, try some dry gas.
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Old 12-31-2005, 12:57 AM   #5
projectrally
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I've run 4 tanks of gas through it. So I don't think it's got anything to do with moisture in the gas tank. I've just changed the coil pack and the plugs, so i don't think it's got anything to do with the ignition system.

But after driving it a little more, let me explain the problem more accurately...

The car runs just fine half the time. Then, all of a sudden, throttle will just disappear. It doesn't matter if I keep it where it is or drop the pedal to the floor...once the throttle goes, the car starts to decel until it decides to fix itself, which it does just as suddenly, and then the car starts accelerating again. Usually, once this cycle starts, it continues: Car runs fine, then throttle disappears and car begins to decel, then throttle returns and car speeds up, then car runs fine again, then throttle disappears, etc.

When I'm around town, this problem usually shows up in first and second gear when pulling away from a stop. The throttle disappears, the engine runs poorly and sputters. The car lurches a bit like it does when a new driver is attempting to learn a manual trans and they don't know how to let out the clutch gently. The cure for the problem is to accelerate. Once the car gets up around 4K, things seem to level out. Keep the car a gear or two lower than you want to be in, and keep the revs high, and the car drives just fine. Sometimes it drives fine anyway. The problem just keeps coming and going. It's there at one stop light, and gone at the next.

The same is true on the highway. The car will run fine at cruising speed for half an hour, then all of a sudden, bam, it starts acting up. Once it gets into the habit of messing up, it's hard to break it. So far the only thing that seems to work consistently is to drop it into 4th and ride with the revs around 4500 (a bit lower works, but 4500 is just where it runs when you're on the highway in 4th). Then, after driving in 4th for a while, i can shift back up into 5th and the problem goes away. For a while anyway.

All i can figure is that somehow when I'm in 4th, I'm in open loop and the car is happy. When I shift back into 5th, the car is fine until it drops back into closed loop. Then things are unhappy. At least, that's my best guess at this point. Please help!
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