TPS voltage

[-LegnumVR4-]

Anyone handy with a multimeter to give me the correct resistance value? Mine was bumped ages ago and my throttle has always been a bit twitchy on/off.

[-LegnumVR4-]

Just want to check if the TPS is the problem for the twitchy throttle. Is there anything in the workshop manuals?

[bernmc]

Where is the sensor? If you let me know I'll see if I can check mine for you, provided it doesn;t involve removing the engine!

[-LegnumVR4-]

Its on the throttle body, the plug is to the right and below that funny looking round cap thing that has a hose coming from the grey cylinder on the fire wall. The plug has a brown/red colour to it and sits on a 45deg angle to the engine, its the one closest to the fire wall behined the intake pipe, not the one in front which looks the same

[-LegnumVR4-]

Any luck? Anyone?

[bernmc]

Any luck? Anyone?

I'll try to have a look for you if I get home before it's dark today. Working tonight, so may be able to look in the daylight tomorrow...

[-LegnumVR4-]

Cheers

[bernmc]

I had a furtle yesterday. Unfortunately, I couldn't for the life of me work out how to get the bloody connector off, and gave up after my screwdriver disappeared into the engine bay ! Wasn't prepared to poke into the wires' insulation. There are also 4 wires into the plug, so I'm not sure if it's just a simple variable resistor...?

If it is, surely if you test yours and get a smooth, linear change of resistance across the throttle range, then it should be ok - you'd expect odd jumps if it was the source of your sticky throttle.

I'll have another go if you're desperate, and can tell me how the plug comes off.. without breaking the damn thing!

[-LegnumVR4-]

Thanks for having a look. U have to remove the little steel clip that is on the plug, it's one of those ones that go 'ping' around the engine bay if u don't keep a hold of it All u do it get a small flat head screw driver and press on the end of the clip from the back of the plug (the clip starts from one side and finishes on the other). The clip should move forward, have a finger on the other side to stop it from flying off into the engine bay.

[bradc]

well, I would measure it, but I don't know what I'm looking for. Any chance on a picture Rhys?

[-LegnumVR4-]

2 photos of the plug which is connected to the TPS.

[psbarham]

Right, here goes, I hope this makes sense.
Symptom: Car was stalling at lights, when idling, its was idling properly and the engine seemed to be hunting for a idling speed. It would rev slightly faster, then slow down again, every couple of seconds.

Reading posts on here I assumed it was my stepper motor, and I took it to pieces to clean it. I couldn't find anything wrong with it however. So having ruled that out I hit the books to try figure out what was causing the problem.

The ECU takes readings from various sensors on the engine to regulate fuel injection etc.. and 2 of these sensors montior the position of the throttle, Idle Position Switch (IPS) and Throttle Position Sensor (TPS).

Basically the ECU puts the car into either an idling mode or a driving mode depending on where it detects the throttle is. When in idling mode its nice and happy to let the engine tick over. When in the driving mode its constantly trying to alter the fuel mix etc for driving conditions. My problem came about because, when I was idling, the ECU thought I was driving.

The accelerator cable, which terminates at the throttle body, is attached to the inlet manifold at the back by an adjustable bracket. This bracket allows you to set a little tension in the cable so you have no slack. Once this is set, you have to then alter the IPS so that your ECU knows where the idle point is.



The IPS/TPS are both housed in the black circular thing attached to the front of the throttlebody. Notice how, when the bolts are loosened its able to turn slightly to allow you to adjust its angle into the throttlebody.

The IPS is just a switch that closes when you take your foot of the accelerator pedal, causing the throttle body to close and in turn close the switch. If you remove the connector from the top you can measure between pins 1 and 2. With the throttle closed, you should measure 0 ohms resistance as the switch is closed. As soon as the throttle cable is pulled and hence opens the throttlebody butterfly, the switch should open and the resistance between pins 1 and 2 go to open circuit. (pin 1 is earth and is the black wire on the connector).

By loosening the bolts slightly (not removing them) you should be able to twist it slighty. You want to tighten it back up at the exact point where the switch is closed, i.e. throttle is closed so switch is closed, as soon as the throttle starts to open, the switch must open too.

[-LegnumVR4-]

The VR4 auto preface lift have 2 sensors that look the same, one at the front of the throttle body and another at the back. Ur photo shows one at the front and looks like an 2.5V6 n/a engine? I would say the one at the front of the throttle body on the VR4's is the idle sensor and the one at the rear is the throttle sensor? CAPS brings them up as being both a Throttle body throttle sensor but with different part numbers: front one is MD614736 rear is: MD614734. The only reason i'm pointing my finger at the back one is its been bumped so it should be out from the factory setting. At one stage i did have the idle adjusted for the rpm idle, it was a matter of pluging in the MUT-II and adjusting the large screw in the hole above the sensor, not sure if this upset things or not but will look into it. I know i have never touched the front sensor but have adjusted the throttle cable a few times so i'll start going over all the bits and bobs to fine out whats going on.

Thanks for the info