Hey, everyone...ive just been under the bonnet poking around with the multimeter, testing the TPS, which i have suspected was a bit dodgey.
Now...when testing the resistance of the top two spades of the tps plug....my multimeter is reporting infinate resistance, untill i open the throttle to about 1/4....the resistance then drops normally as expected.
I was wondering if this means that my tps needs to be adjusted, and if so...
how do i adjust it?...do i adjust it such that it reads infinate resistance on idle and drops as soon as you depress the accelerator?

I really not too sure about how to go about this one,....any help from magna guru's would be greatly appreciated

Thanks,
Daniel

Not sure how there sposed to be set on a magna, haven't had a peek yet, no need to :P but to adjust a TPS is usually two locking screws/bolts on the tps and once loosened you rotate it in the slots either side of it, have a try and see what it does to your res.

Matthius

Thanks for that Matthius...after doing a bit of reading around on the interenet, the adjustment is as follows
Take the plug off , loosen adjustment screws, rotate the TPS anticlockwise..check that the top two plugs is not an open circuit. Rotate the plug slowly clockwise untill the plug becomes an open circuit...tighten up adjustment screws....thats it.
I have noticed it to be quite sensitive. i.e. small movements in the tps, results in large differences in the throttle readout.

Thanks again for the help

Daniel

You also have to put a 14mm feeler gauge under the throttle lever/stop.I used a 10c piece which is close.

Eagleaus I assume you mean a 1.4 mm guage?

Is this also the correct setting method for a 3.5 TL (don't kill me, I don't know if the TF is a 3.5)?

right....following the sugestion of the spacer...i have re-done testing the tps.

The results i have gotten are as follows:
3.98 ohms rotated fully conter-clockwise
4.23 ohms rotated fully clockwise

I am not getting an open circuit through the rotation, as i should be. ( i thought i was, but that was only because i was being dumb with the multimeter and was using the wrong scale 4Kohms as opposed to 40K)

I am testing it the following way
1) Spacer under throttle stop screw (0.65mm...is what the haynes service manual i have just gotten says)
2) multimeter set on the 40K ohms scale
3) testing the top two spades on the tps plug

Is their something i have missed/(done wrong), or has my tps borked it?

Thanks for the replys so far guys :)

Eagleaus I assume you mean a 1.4 mm guage?

Is this also the correct setting method for a 3.5 TL (don't kill me, I don't know if the TF is a 3.5)?

The TF are 3Litre engines, as far as the feeler guage size goes...my hanes manual says 0.65mm

can anyone dumb this down for me? ... im sure there are others pulling their hair out trying to under stand this :P

can anyone dumb this down for me? ... im sure there are others pulling their hair out trying to under stand this :P

Basically i am trying to adjust the Throttle Position Sensor(a sensor which tells the engine computer how much accelerator you have put down). The Computer uses this information to work out how much fuel to inject into the cylinders, and as far as i know...when to change gears for the auto.
If this sensor is out of wack or faulty, it can cause an occasional unstable idle (because the engine computer thinks that the throttle is moving), and occasional surging.

ahhh got ya ;)... thnx ... im dure u helped half the forum to who were to embarrassed to ask :P

My engine is idling no problems. Only fun that I am having is that I have to depress the accelerator pedal to get the auto to shift up to 5th from 4th.

Maybe it is just a case of waiting for the ECU to relearn the change in TB's (got one from EZBoy. Just wanting to make sure I didn't stuff the install).

Funny thing is the guy across the road is a fitter and turner working for BP and he said he would be able to fit the TB to a lathe for machining. Yes / no? Would it make it easier?

Seems he did this for working on the TBs for his mustang.

Tim

My engine is idling no problems. Only fun that I am having is that I have to depress the accelerator pedal to get the auto to shift up to 5th from 4th.

Maybe it is just a case of waiting for the ECU to relearn the change in TB's (got one from EZBoy. Just wanting to make sure I didn't stuff the install).

Funny thing is the guy across the road is a fitter and turner working for BP and he said he would be able to fit the TB to a lathe for machining. Yes / no? Would it make it easier?

Seems he did this for working on the TBs for his mustang.

Tim

From what I've heard ez-boy and rpw say this is difficult with a magna TB as the walls aren't very thick, there isn't much meat to machine out.

Matthius

The only way i can get the tps to behave as described in the haynes manual(getting open circuit) is by
1) testing the bottom two spades of the plug. (manual led me to believe it was the top two)
2) Rotate plug fully clockwise whilst standing infront of the car, then back it off (counterclockwise)untill you get an open circuit.(manual indicates the opposite) :nuts:

Ah well im getting completely lost, i have had other people look at the manual and they think the same as me
Can anyone confirm that the way i have done it is correct?

Argh, im getting way out of my depth here....i think ill have to get it looked at by someone next time i get a service

Thanks everyone for your help

Daniel

The only way i can get the tps to behave as described in the haynes manual(getting open circuit) is by
1) testing the bottom two spades of the plug. (manual led me to believe it was the top two)
2) Rotate plug fully clockwise whilst standing infront of the car, then back it off (counterclockwise)untill you get an open circuit.(manual indicates the opposite) :nuts:

Ah well im getting completely lost, i have had other people look at the manual and they think the same as me
Can anyone confirm that the way i have done it is correct?

Argh, im getting way out of my depth here....i think ill have to get it looked at by someone next time i get a service

Thanks everyone for your help

Daniel

I realise that Daniel's problem has long been solved or abandoned, but after running into the same problem and not finding a solution on this forum, I thought I'd save anyone else the headaches I've had.

Symptoms: engine began to stall at idle when the air conditioner was turned on. The diagnostics did not indicate any problems but I investigated the Throttle Position Sensor anyway, suspecting that the engine was not going into closed loop idle because it didn't realise the throttle was closed.

The Haynes manual proved to be quite misleading, having identified the wrong terminals as Daniel suspected. The closed throttle position switch is actually tested by checking continuity between the bottom two terminals, identified on their illustration 4.41 as Terminals 1 & 2, not 3 & 4 as they indicate in the text (they also incorrectly refer to the illustration as illustration 8.41). A trip to the library to refer to the Gregory's manual confirmed this.

Gregory's also specifies a 0.45 mm feeler gauge for models without cruise control and 1.4 mm for models with cruise control. Given the quality control in this section of the Haynes manual, I am inclined to use these figures rather than rely on the 0.65 mm specified by Haynes.

Hopefully Haynes will sort this out when they update it to include TJ II/KJ II (as announced at http://www.haynes.com.au/prod1979.htm).

I realise that Daniel's problem has long been solved or abandoned, but after running into the same problem and not finding a solution on this forum, I thought I'd save anyone else the headaches I've had.

Symptoms: engine began to stall at idle when the air conditioner was turned on. The diagnostics did not indicate any problems but I investigated the Throttle Position Sensor anyway, suspecting that the engine was not going into closed loop idle because it didn't realise the throttle was closed.

The Haynes manual proved to be quite misleading, having identified the wrong terminals as Daniel suspected. The closed throttle position switch is actually tested by checking continuity between the bottom two terminals, identified on their illustration 4.41 as Terminals 1 & 2, not 3 & 4 as they indicate in the text (they also incorrectly refer to the illustration as illustration 8.41). A trip to the library to refer to the Gregory's manual confirmed this.

Gregory's also specifies a 0.45 mm feeler gauge for models without cruise control and 1.4 mm for models with cruise control. Given the quality control in this section of the Haynes manual, I am inclined to use these figures rather than rely on the 0.65 mm specified by Haynes.

Hopefully Haynes will sort this out when they update it to include TJ II/KJ II (as announced at http://www.haynes.com.au/prod1979.htm).

Hey mate, im planning on checking mine as i took it off to clean throttle body and stuff, and now it idles to high. Might even have a look tomorrow to familiarise myself with these terminals and the general set up. I'll probably be picking ya brain haha, im yet to get myself a manual. Only have the Mitsubishi one on my laptop.

Ive got both a mitsubishi manual on cd, and a gregorys manual. Both say to connect an ohmmeter to terminals 1 (sensor ground) and terminal 2 (closed throttle position switch). As you have mentioned, the correct terminals are the bottom two. Both manuals state that there should be continuity when the tps is turned fully counterclockwise, and then you turn it slowly clockwise till continuity is lost and tighten the screws at that position. Now Im wondering if the manuals have a misprint, as the two tps I have do it the opposite way around, ie no continuity when turned fully counterclockwise, and continuity when turned fully clockwise. Wondering if anyone has come across this already, Im thinking the manuals are either wrong, or both my tps are faulty?

Hey mate, im planning on checking mine as i took it off to clean throttle body and stuff, and now it idles to high. Might even have a look tomorrow to familiarise myself with these terminals and the general set up. I'll probably be picking ya brain haha, im yet to get myself a manual. Only have the Mitsubishi one on my laptop.

Did you mark the TPS position before removal and return to it's original location?

Good chance it's idling higher due to a clean TB and addtional airflow but I would expect the ECU to adjust this if the car is left idling for 10mins or so. ( as per the ECU reset when the battery is disconnected. ) I forget now exactly the time frame.

The ECU, ISC and TPS work together.

With the throttle closed, the TPS switch is closed which signals the ECU to control idle speed with the ISC.

With the throttle open, the switch is open (causing the ECU to release control of engine speed through the ISC) and the potentiometer tells the ECU how much throttle you have on. This also controls change points of the auto trans.

Poor idle or stalling can be caused by the TPS being out of adjustment, or a failed ISC motor. The ISC is a stepper motor that winds its nose in and out in an air passage to control the flow of air into the engine to maintain idles speed under different load conditions. If one coil in it fails, the motor can wind in only one direction, resulting in a very low idle, or a very high idle.

If the potentiometer part of the TPS is faulty it can cause erratic shift points. Some people get the impression at this stage they need a new transmission.

Testing ISC: Remove the ISC, plug it in, turn ignition on but don't start. The nose should move in and out. If it only moves in one direction, and then sits there and jiggles around, it is stuffed.
Testing TPS: (ignition on, engine not running) Find the right contacts to test the switch, ON with no throttle, OFF when you move the throttle linkage slightly.
Find the right contacts and check that the resistance reading increases smoothly while you open the throttle slowly to full open.

Wicked stuff, cheers mate.

Thats some good info there

Will have a crack tomorrow.

Cheers

The ECU, ISC and TPS work together.


Testing ISC: Remove the ISC, plug it in, turn ignition on but don't start. The nose should move in and out. If it only moves in one direction, and then sits there and jiggles around, it is stuffed.
Testing TPS: (ignition on, engine not running) Find the right contacts to test the switch, ON with no throttle, OFF when you move the throttle linkage slightly.
Find the right contacts and check that the resistance reading increases smoothly while you open the throttle slowly to full open.

Can someone provide more details on Testing the TPS in the manner described above. Which wires to measure across etc.

I assume it is done with the wires connected and pushing the multimeter probes through the back of the harness(?). If resistance measuring are there live wires to worry about?

My TF is running roughly off idle. Running with the TPS harness disconnected or the body rotated either way makes no appreciable difference. Is that normal??

Thank you