Subaru Forester Owners Forum banner
1 - 6 of 6 Posts

·
Registered
1999 Forester S Turbo 5MT
Joined
·
1,960 Posts
Discussion Starter · #1 ·
I asked a question about TPS and spark plugs a while ago but this is not a question, more an observation that I hope may be helpful to others. I have a 99 UK S turbo and recently replaced the MAF and TPS, both genuine Subaru items. There are one or two posts relative to TPS settings on various forums but I think these are a bit vague about the actual readings. The voltage is measured across the red and white wires which are the middle and back ones from the plug as in my attached pic, the red and yellow wire at the front is not used for this measurement. To access the core of the cable, I sharpened the tips of the probes of my multimeter, thats what the "wounds" are. Most advice says that between 0.4 and 0.55 volts is acceptable at idle with the engine warmed up. I have found that a very specific range works on my car - 0.46 to 0.48V. If I set it to between 0.5 and .055v the throttle seems to have lost it's bite/response. I have been setting it and then driving for around 100 miles mixed use before I reset it and this has been done over a period of about three weeks with variable weather. The screws for setting the TPS are as shown in the other picture as is the location of the TPS, next to the dump valve and under the idle air control solenoid. You can see one on the top and the other one is directly below and will need a long, at least 10", screwdriver to access it. Adjusting that specifically is time consuming and the physical movement of the TPS is very small to get such a specific voltage, and you will have to lean right over to get the probes into the wires for a reading which is hard on the knees. Perhaps this is perculiar to my Foz?
 

Attachments

·
Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
Joined
·
5,926 Posts
Are you sure you have your units correct (or measuring it correctly?)as the manuals I have show:-

MY97 Impreza Turbo

Fully closed 0.5+/-0.3 V
Fully open 4.3+/-0.3V

MY01 Forester S Turbo and MY03 XT

Fully closed 0.2-1.0V
fully open 4.2-4.7V

Power supply to TPS 5V
All measurements taken at the ECU and I presume between signal wire and ground.

For the MY97 the TPS has three wires 1)Black - ground, 2)Red - Supply and 3)White - signal.

Surmising yours are the same as this then you are measuring between signal and supply which would indicate you are measuring the voltage drop across the coil, hence the small readings.

EDIT:
Have attached the MY99 TPS data on pdf.....(same as MY97)
 

·
Registered
1999 Forester S Turbo 5MT
Joined
·
1,960 Posts
Discussion Starter · #3 ·
Hi Don. Bad syntax on my part I think. The settings I am using are at idle (fully closed?) and fall within the parameters you suggest but just a lot more specific, that is to say 0.46-0.48v at idle but fully open I am getting around 4.5v. I did check about the wiring too because I had problems sorting it all out in the begining. I am going across earth and signal, not the 5v supply line. I think this might be a bit of an anomaly to my car but if I change those settings, the throttle response seems to be affected for the worse. All going well, the Foz is going in this weekend for Uncle Bob to fiddle with the ECU.
 

·
Registered
1999 Forester S Turbo 5MT
Joined
·
1,960 Posts
Discussion Starter · #4 ·
Don, help please. I have the diagrams for the ECU and the specific terminals to set the TPS but when I remove the ECU, I see three block connectors of 4x9 pins (I think) and can't relate that to the parts diagram which shows 3 rows of 13 pins. I'm not even sure which is B136, I think it's the one on the right but I'm not sure. Can you sssist in decifering this please as I feel a bit of a twit but would like to make sure the TPS is set correctly. I'm off for my second session with Bob Rawle in 4 weeks as a number of issues showed up on the first day mainly that I fitted an outboard EBC which messed up the mapping process because the ECU couldn't talk to it. Bob has instructed me to re activate the stock BC for the next visit, but I will post when it's all done. Ta.
 

·
Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
Joined
·
5,926 Posts
Check out Simon's (JGM) help page here..............

JollyGreenMonster.co.uk

Yours should equate to the MY99-00 ECU pinouts and I/O signal sheets.
Usually one of the sockets on the ECU will be marked with its number.
 

·
Registered
1999 Forester S Turbo 5MT
Joined
·
1,960 Posts
Discussion Starter · #6 ·
Thanks Don, I'll have a go at that this weekend.
 
1 - 6 of 6 Posts
Top