Throttle position sensor
 

Hi All,

MY99 Classic UK turbo version 5 with EJ205 engine.

Having a bit of bother with high & lumpy idle. When I start the car from cold the revs will shoot up to about 1800 rpm & immediately drop to a lumpy idle hunting between 1350 to 1450 rpm. When the car is up to temperature the idle rpm will increase slightly & idle lumpy between 1450 to 1550 rpm.

After say a few miles driving I will stop at a junction, when I disengage the clutch plate at standstill the revs will shoot up to about 2100 rpm dropping back over about 5 or 6 seconds to 1650 to 1750 rpm & hunt between that higher ranges as long as I stay still. Am also getting a bit of jerkiness on light throttle in every gear, haven’t even got to high throttle yet as am still running engine in after complete rebuild.

What would be the sort of factory spec if you like in regards to the voltage range between the throttle plate in the fully closed position through to the fully open position? I back probed mine & currently have 0.76 volts in the FCP & 4.53 volts in the FOP. The sensor works as it should increasing & decreasing in the proper manner as I rotate the throttle plate. Was just wondering if this was within factory spec for a uk turbo as I have read on forums that others have been getting 0.45 to 4.60 volts but they were discussing an STI. I don’t know if it’s the same for an STI as it is for a turbo? There is a bit of difference in the FCP reading of 0.76 so was just thinking that if this was indeed to be high then it would be telling the ecu to idle higher through the signal wire. Didn’t want to remove the sensor just yet as hear they can be a bit fiddly to set back up. Also please refer to the list of work below I have done to date to try & rectify these issues, if you have any other suggestions believe you me they will be more than welcome!!!!!!!:brickwall

I have cleaned tested & then changed the ICV, cleaned then checked the throttle plate for correct position, checked throttle cable not too tight, installed new maf sensor, new pressure sensor, new 02 lambda sensor, new turbo intake pipe, new OEM inlet manifold gaskets & torqued down to 25 nm, new magnecor ht leads, plugs have only 12 k & are gapped properly, checked all pipework & vac lines off manifold. Checked all fuel pipework from the tank to the injectors with car running. Then I got access to the same car as mine that was running well 5 minutes prior & changed over the air box pipes through to turbo intake pipe, changed out the intercooler, Y pipe & dump valve, changed the boost solenoid & associated hoses, the pressure exchange solenoid & associated hoses, changed over ecu & checked grounds. The problem still persists!!!! I have an inlet manifold PCV valve in the post.



Any feedback would be much appreciated. Cheers Paul.

TPS needs to be between 0.45v and 0.55v full closed and around 4.6-4.7v fully open. Just get a reading on an accurate volt meter and then loosen the two holding screws and rotate till you get the right voltage fully closed.

Had this issue on mine and solved by doing this.

Thanks for your reply Scoob.

Will give it a bash.

Cheers Paul.

Scoob never got a chance to get to it today but will get to it tomorrow.


When you say rotate it could you elaborate a bit further please?


My TPS is elongated (see below, top one for reference) this would not facilitate rotation of the TPS once the screws were slackened but it would allow a lateral/side movement. So is it slacken off the 2 screws then slide the TPS side ways until the aforementioned readings are achieved?


https://cimg4.ibsrv.net/gimg/www.sco...d023a45d10.jpg


Or is it a case of taking the TPS off the TB completely to allow access to the internals to rotate the potentiometer inside until the desired range is achieved? Then refit it to the TB - jobs a good one? :freak3:


Cheers Paul.

When you slacken the 2 screws it wil rotate as it is pivoting from the centre. Make very small movements and use a pin through the centre wire to take your voltage from.

Thanks for the prompt reply Scoob.

Understand now mate when you mention it is on a central pivot point, was getting a bit confused there :wonder: but that's not hard.

Yeah I used the needle technique when back probing my original readings, works well.

Thanks very much for the help, hopefully it will be sorted out very soon :thumb:

Cheers Paul.

No worries Paul, let me know how you get on and hope you get it sorted.

Job is a good one Scoob :luxhello:


Set up TPS & the car is now running & idling bang on the money :thumb:


Thanks for all your help, very much appreciated mate.


Roll on another 200 miles so I can drop the Millers competition mineral running in oil & the jdm black filter & get in the Millers competition fully synthetic triple ester & new jdm black filter & see if the old girl has still got some legs about her :norty:


Am chuffed to bits.


Cheers Paul.

Good stuff Paul!

Glad you got it all sorted. I was in the same boat as you a few weeks ago so was fresh in my mind after it worked for me.

Glad I could help.

So it was tps?

Chuffed to bits, thanks again Scoob, :thumb:

Hi veerinder,


Yes it was the throttle position sensor.


I think what has happened is I have had my engine in & out 3 times in the last 2 months & the last time I put it back in I think I must have knocked the sensor when I was refitting the intercooler & intercooler Y pipe onto the turbo discharge nipple. This had moved the potentiometer slightly in turn increasing the voltage that was being sent down the ECU signal wire.


When I back probed the TPS I had 0.76 volts with a fully closed throttle plate (butterfly valve). When I rotated it to fully open I had a reading of 4.53 volts.


Loosened the screws & moved it until I had a reading of 0.483 volts with a fully closed throttle plate, buttoned it up & the job was a good one :thumb:

Ah ok ive got issues with mine too. So does tps get adjusted while csr is running? Because at the moment with mine im running it on cable as mine doesn't stay on its turns off if pedal isn't pressed so its pulled on csnle to about 1k rpm lol

Hi Veerinder,


Not with the car running.


Pop the intercooler & IC hoses off to allow better access & so that you can see the throttle plate to confirm it is fully closed & not slightly open due to carbon build up. Clean out as necessary. Remove the idle control valve to also aide access & clean same.


loosen the 2 adjusting screws on the TPS. The bottom screw was awkward to break on my EJ205 as the coil mounts are at that side of the inlet manifold - not a lot of room. I removed the coil & the pressure sensor to give me more room to work with the meter leads & gain access to the bottom TPS screw - it only takes a couple of minutes & gives you much more room.


Don't know what like you are with electrics but I will assume for now you will know how to use a meter & be able to carry out the checks to be able to establish what lead is what. If you are unsure how to do this let me know & I will explain how to test to find what wire does what without having a wiring diagram.


There will be three wires on the TPS
Positive
Ground
ECU signal wire


After establishing what wire does what. I was unable to back probe directly into the connector with my fluke meter leads to get readings so this is how I did it.


Get a couple of very small sewing needles, pull back the loose sheath & push a needle into the ground wire through the insulation until it makes a good contact with the inner core. Do the same with the ECU signal wire. Stagger the needles so they are not too close to each other to provide you with some room to work with between the leads.


Connect your meter leads to the needles, crocodile clip type accessory's are good in this situation as you can make your circuit & you have both hands free to mess around. Rotate the TPS potentiometer until the desired voltage is seen on the meter then tighten the screws (remember to check throttle plate is fully closed at this time). Rotate the throttle plate to fully open & check reading, release throttle plate to the fully closed position & repeat the process check each time you have the same readings. Here what I set mine at & it is spot on.


In the fully closed position I set the TPS to 0.483 volts.
After rotating to the fully open position I had 4.258 volts.
Total variation of 3.775 volts.
Apply insulating tape around the area's you probed with needles, pull loose sheath back over the 3 wires.


Refit removed parts & hopefully on restart the car will be fine :thumb:


Hope that helps.

P.S. If you can't get the bottom TPS screw out then you can always quickly whip of the throttle plate complete, couple of minutes, 4 bolts & 2 hose connections. But then you will need a new gasket, a couple of pounds from ICP or such like.