TPS reading is unstable.

Whizbang · 06-01-2010, 07:32 PM

I had a haltech tps for a long period of time but have always had issues with inconsistant readings. With the accel wizard open and the car not running, i get varying readings of 0 %/s to 19.7 %/s. The moment the car is running, its all over the place up to over 150%/s at time. This is all without me touching the pedal. This is obviously kicking the accel enrichment on and makes the car buck and / or run lean.

I thought the tps was bad, replaced it with a OEM hyundai tps (had a d shaft so i went with it). Seems to be a narrower range than the haltech tps but i have getting the same problem with the readings. the car is also immedately running worse, even with the tps calibrated...

Im figuring im getting some interference from the other wires in the system since all of the wires are ran through the same place in the firewall and i do not have shielding or shielded wire.

Any other thoughts? I have looks at my grounds several times, the voltage is constant to the TPS when the car is off. Ill have to check with it running.

i have been trying to figure this is out for at least a month and its rather fustrating.

NoDOHC · 06-05-2010, 08:25 PM

If you unplug the wiring from the TPS, but leave the wiring otherwise intact, does the behavior continue? If so, it is noise.

If not, it may be noise, but is likely due to mechanical vibration of the wiper in the TPS.

If there is no jumping with the TPS unplugged, get an ohm meter and watch the resistance between the wiper of the TPS (center terminal) and one of the other two. If it moves while the engine is running, the TPS is experiencing too much vibration. you can couple it with rubber hose to the shaft (old trick that works pretty well) and mount it on rubber.

Whizbang · 06-06-2010, 02:40 AM

ill have to give that a try tomorrow

RotaryProphet · 06-06-2010, 08:37 AM

You may also try replacing the TPS with a pair of resistors; measure the resistance between +5v and signal, and between ground and signal, and pick up some resistors in that ballpark. Then just stick them on the wires. If your signal is stable, you have a TPS issue. If it's still wonky, then shut the engine off. If it's -still- wonky, it's your wiring or the circuit in the ECU. If it stabilizes with the engine off, it's likely interference.

06-01-2010, 07:32 PM	#1
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp Posts: 3,190 Rep Power: 20	TPS reading is unstable. I had a haltech tps for a long period of time but have always had issues with inconsistant readings. With the accel wizard open and the car not running, i get varying readings of 0 %/s to 19.7 %/s. The moment the car is running, its all over the place up to over 150%/s at time. This is all without me touching the pedal. This is obviously kicking the accel enrichment on and makes the car buck and / or run lean. I thought the tps was bad, replaced it with a OEM hyundai tps (had a d shaft so i went with it). Seems to be a narrower range than the haltech tps but i have getting the same problem with the readings. the car is also immedately running worse, even with the tps calibrated... Im figuring im getting some interference from the other wires in the system since all of the wires are ran through the same place in the firewall and i do not have shielding or shielded wire. Any other thoughts? I have looks at my grounds several times, the voltage is constant to the TPS when the car is off. Ill have to check with it running. i have been trying to figure this is out for at least a month and its rather fustrating. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

06-05-2010, 08:25 PM	#2
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	If you unplug the wiring from the TPS, but leave the wiring otherwise intact, does the behavior continue? If so, it is noise. If not, it may be noise, but is likely due to mechanical vibration of the wiper in the TPS. If there is no jumping with the TPS unplugged, get an ohm meter and watch the resistance between the wiper of the TPS (center terminal) and one of the other two. If it moves while the engine is running, the TPS is experiencing too much vibration. you can couple it with rubber hose to the shaft (old trick that works pretty well) and mount it on rubber. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

06-06-2010, 02:40 AM	#3
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp Posts: 3,190 Rep Power: 20	ill have to give that a try tomorrow __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

06-06-2010, 08:37 AM	#4
RotaryProphet Rotary Fanatic Join Date: Sep 2008 Posts: 147 Rep Power: 17	You may also try replacing the TPS with a pair of resistors; measure the resistance between +5v and signal, and between ground and signal, and pick up some resistors in that ballpark. Then just stick them on the wires. If your signal is stable, you have a TPS issue. If it's still wonky, then shut the engine off. If it's -still- wonky, it's your wiring or the circuit in the ECU. If it stabilizes with the engine off, it's likely interference.