1993 Chimaera 4.0 warm low-rpm hesitation and unusual TPS
Discussion
Hi everyone,
I’m trying to track down a hesitation on my 1993 Chimaera 4.0 with the Lucas 14CUX ECU. When the engine is cold, it pulls cleanly even from low revs. Once warm, it noticeably hesitates or judders at around 1100–1600 rpm, in third gear as well as fifth. Above that range it drives normally. If I accelerate firmly from low revs, there is a brief hesitation and then it pulls well.
The car has a TPS kit fitted, using a Colvern CP17/715/NS-I, ES220 5 kΩ sensor. It previously drove well with this kit installed, so I don’t want to assume the TPS is necessarily the cause of the warm-running problem.
I’ve been checking it with RoverGauge and a multimeter:
At closed throttle, the best setting I can achieve is about 18% absolute / 9% corrected in RoverGauge.
The TPS signal measures 0.93 V at closed throttle. Even with the sensor removed from the throttle shaft but still electrically connected, turning it by hand cannot bring the signal below 0.93 V. It rises smoothly to about 4.3 V at the other end.
The 5 V supply is present, and the connector wiring appears to match the sensor: yellow to blue (supply), red/black to black (ground), and red to red (signal).
RoverGauge shows roughly 82% absolute at fully open throttle.
RoverGauge shows no fault codes. Coolant temperature rises normally and the lambda trims respond.
My understanding is that 0.93 V at closed throttle is high for the 14CUX, but I’m unsure whether this particular Colvern sensor has a different usable range, whether the sensor or kit has developed a fault, or whether the warm hesitation is a separate ignition or fuelling issue.
Has anyone used this Colvern kit on a 14CUX Chimaera and seen similar TPS readings? What would you check next to establish whether the TPS is responsible for the warm low-rpm hesitation?
Many thanks for any advice.
I’m trying to track down a hesitation on my 1993 Chimaera 4.0 with the Lucas 14CUX ECU. When the engine is cold, it pulls cleanly even from low revs. Once warm, it noticeably hesitates or judders at around 1100–1600 rpm, in third gear as well as fifth. Above that range it drives normally. If I accelerate firmly from low revs, there is a brief hesitation and then it pulls well.
The car has a TPS kit fitted, using a Colvern CP17/715/NS-I, ES220 5 kΩ sensor. It previously drove well with this kit installed, so I don’t want to assume the TPS is necessarily the cause of the warm-running problem.
I’ve been checking it with RoverGauge and a multimeter:
At closed throttle, the best setting I can achieve is about 18% absolute / 9% corrected in RoverGauge.
The TPS signal measures 0.93 V at closed throttle. Even with the sensor removed from the throttle shaft but still electrically connected, turning it by hand cannot bring the signal below 0.93 V. It rises smoothly to about 4.3 V at the other end.
The 5 V supply is present, and the connector wiring appears to match the sensor: yellow to blue (supply), red/black to black (ground), and red to red (signal).
RoverGauge shows roughly 82% absolute at fully open throttle.
RoverGauge shows no fault codes. Coolant temperature rises normally and the lambda trims respond.
My understanding is that 0.93 V at closed throttle is high for the 14CUX, but I’m unsure whether this particular Colvern sensor has a different usable range, whether the sensor or kit has developed a fault, or whether the warm hesitation is a separate ignition or fuelling issue.
Has anyone used this Colvern kit on a 14CUX Chimaera and seen similar TPS readings? What would you check next to establish whether the TPS is responsible for the warm low-rpm hesitation?
Many thanks for any advice.
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