Throttle hang... position sensor data logging makes no sense

sjscott

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Nov 30, 2018
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El Mirage, AZ
Ok, kind of long description but trying to be as throught as I can. My recently acquired 98 Contour SVT has a bad problem with throttle hang. It's throwing a check engine light for code p1120 (tps, ratch too low) and when first starting it up it runs ok but seems as it warms up it gets continually worse. At first the revs drop like normal, then it starts to not drop revs for 3-5 seconds or until I slow down to about 5 mph, then it starts to have the revs raise in neutral for 15-20 seconds up to around 4k rpm. I've reset the ECU, cleaned and tested the idle air control valve, replaced the TPS, cleaned the throttle body, and now at a loss what is causing the problem. The data logging for the throttle position sensor shows that the level it detects when the throttle is at idle seems to step/raise up the longer I drive. Starting at 6% throttle at idle (during which it runs fine) going up to around 7% (throttle hangs a little but drops after a few seconds) then jumping up to around 17% (revs going up to 4k in neutral with foot off the gas and wanting to stay there for about 15 sec.) Any help is greatly appreciated!
IMG_20181129_212836.jpg
 

SicilianSVT

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Dec 11, 2018
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Brownwood Tx
I have had this issue in mine. The regular v6 contours use a different TPS than the svts and the svts are quite difficult to find. I would start there and make sure you have the right one.


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sjscott

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Nov 30, 2018
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El Mirage, AZ
I'm about to get another TPS soon if I can't figure anything else out but it does turn the right direction and when tested it showed .8 volts at idle and 4.66 volts at full throttle. Though I did notice today that it's not just the throttle at idle that changes, when it's running fine the tps readings on the OBD2 range from 7% at idle to 74% at full throttle, but when the throttle hang gets really bad the readings are from 17% at idle up to 92% at full throttle. When I put it in neutral the rpms stay wherever they were when I push the clutch in/let off the gas and the idle stays high even though it's still reading that the throttle position is back at idle (the higher idle position of 17%) and the rpms stay there until I stop completely then it drops down to about 1100 rpms. I'm wondering if the ECU has some sort of fault but I'm trying to stick to the cheaper fixes first.
 

SicilianSVT

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Dec 11, 2018
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Brownwood Tx
It could also be a vacuum leak. My svt has done this as well. The small hoses on these cars overtime become brittle and crack. I replaced most of mine and it still does it sometimes so i figured i may has missed one. If its not the TB i would check all your hoses as well.


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sjscott

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Nov 30, 2018
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El Mirage, AZ
Ok, so I think I have this fixed, knock on wood. I pulled out the PCM so I could get the number off it to order a new one. As soon as I got it out I could see there was condensation between the pins and the wiring harness. Gave it a light spray of electrical contacts cleaner, wiped off the blue rubber seal/gasket that slips over the pins and then between the pins with a q-tip to make sure everything was dry. This was 5 days ago and it's running like it should be, haven't had it rev hang once. Also the throttle position has been reading consistently at 16% ever since. Still odd that these cars don't read anywhere near 0% at idle but it's running like it should so it's not a problem. Now I can move on to changing the leaky water pump and a dead o2 sensor.
 

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