What happens if you unhook the TPS and start your car?

[ArlyDude]

What happens if you unhook the TPS and start your car?

I'm wondering if this is the problem to my cold start hesitation and I wanted to see what happened if I just unplugged it. I'm afraid the motor will just rev all the way up.

 

[carguy07]

Could not rev much, the throttle is closed. I would not mess with unplugging it. Get a scan tool and see what it is reading.

 

[ArlyDude]

I got a code scanner. I am just tired of this hesitation everytime I start her. It goes away after I step on the gas hard for about 5-10 seconds. Also, I am down about 100hp according to my gtechpro.

 

[KenH]

Unhooking the TPS will set a check engine light. I don't think it will cause the car to rev out of control, but I'm not sure how it will react.

To test it, you can measure the voltage on the TPS sensor or via a scanner with the key on, but the motor off. Throttle closed, the voltage should be around .5V and at wide open throttle it should go up to something greater than 3.5V, preferably closer to 4V or so.

When opening and closing the throttle slowly, the voltage should raise and lower smoothly without suddenly jumping around which could cause erratic part throttle operation. If the voltage does not raise much above 3.5V, the car may not go into WOT (open loop mode) which could put it down on power as the car will try to control A/F using the O2 sensors which it shouldn't in open loop mode.

If you measure at the sensor rather than using a scanner, you have to allow for .1 to .2V cable harness drop by the time it gets to the PCM.

 

[dansauto]

idle hang=leaking intake manifold, TPS out of range will through a check engine light, cold start hesitation is probably air temp sensor not TPS. Put a scan tool on and check valuse

 

[ArlyDude]

Where is the air temperature sensor? How much are they? Are they hard to replace?

 

[Bill B]

What do you mean by hesitation? Is it hard to start? Does it stall if you try to accelerate when cold? If it is hard (long cranking) to start it could be a fuel line check valve. That was more prevalent on earlier cars (gen 1) The pressure drops and has to build back up before the car will start.