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Author
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Topic: WTF with TPS?
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BCINGUU
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Member # 2397
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posted
 
 
Any sensor / PCM gurus out there?
I tracked down a problem with my TPS that was causing numerous idle, economy, and drivability problems. The TPS voltage was essentially not changing at all during driving. I replaced the TPS sensor but that did not help.
Turns out the reference and sensor return voltages were both 5V. On the wiring diagram, the TPS, EVP, and MAP sensors all have the same reference voltage connection (5V) and all sensors on the car have the same return wire (should be 0V).
Both the reference and return wires end up back at the ECU (pins 47 and 24 or something like that).
Just to see what would happen, I grounded the return wire. Probably not supposed to do that but what the hey. By doing so, I brought the return voltage down to 0 like it's supposed to be and the TPS started working correctly. Now the TPS output is between .94 and 4.5 or so volts and the car is running much better. So I left it grounded and drove it in to work today.
However, this is a band aid. What's really wrong with my car?
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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BCINGUU
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Member # 2397
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posted
Oh no! Double post!
[ July 19, 2005, 03:55 PM: Message edited by: BCINGUU ]
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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BCINGUU
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Member # 2397
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posted
Any help? I can't believe I have you all stumped! ;-)
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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92coupe
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Member # 1957
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posted
i can have a better answer for you later on but off the top of my head:
sounds like your pcm has a bad ground and/or those 2 pins broke loss and dont have a connection to ground.
if you have a friend that upgraded there pcm try out the stock 1 to see if it works correctly.
and grounding those 2 seperately is not "bad" the manufacturer puts most sensors ground through the pcm so they all share a common ground. also to protect against bad grounds. hope a helped a little.
Justin
Posts: 1209 | From: antioch | Registered: Oct 2002
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BCINGUU
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Member # 2397
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posted
Thanks for the reply, that does validate my action and I feel a little less guilty about it! ;-) The car is running great now and I have'nt had a problem since I did this.
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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Wildfire532FB
CAFords OG
Member # 1482
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posted
how did you check the volts on the TPS? and how was the car running that you knew something was wrong with it?
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68 Fastback
84 CJ7
94 HMMWV
95 GT
03 F350
17 Fusion Hybrid
Posts: 17578 | From: 530 | Registered: Jun 2002
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BCINGUU
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Member # 2397
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posted
Measured TPS between black and green wires off the TPS. You can jam a test lead into the back of the harness connector from a DVM.
Some of my Symptoms:
1. Idle would drop below set point upon release of accelerator - driving down the road, come to a light, let off the gas, car almost stalls.
2. Rough idle and hunting
3. Could not adjust idle screw to let idle go below 800 without the car dying
4. EEC was using the altitude spark table, not the sealevel one
5. Major hesitation on Heavy acceleration
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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