I have this Subaru Outback, it needs repairing a lot and it costs me a fortune. So I’ve started attempting some repairs myself. I’m not naturally mechanical so I only attempt jobs where I think I might have a chance – that is, jobs which are light on the grease and torque-wrenches and do not involve removing the engine for example. Definitely no welding!
For some time I have noticed two puzzling symptoms with this car:
- The car sometimes lurches forwards or backwards, especially on the highway
- Sometimes, but not always, the engine revs go up to 2000 rpm or more when stopped at traffic lights
I thought the first one must be mechanical, a worn bearing, excessive play in the 4WD system or something like that. The second fault had to be electronic since the idle speed is electronically controlled.
After doing a lot of reading of Subaru forums, car repair guides and whatnot, I realised that both these problems may be related and caused by a faulty Throttle Position Sensor. The high idle speed is because the engine computer thinks I’m pressing the accelerator when I’m really not, and the lurch happens as I lightly press the accelerator on the highway and the engine computer misinterprets it as me stomping on it – I went for a test drive to confirm this, the lurch even happens when I’m using cruise control.
So I had a look around some spare parts sites and eBay of course for a new Throttle Position Sensor. Now if I was driving a Ford, a new TPS would cost me $25. But a Subaru TPS? How about $400!
Not wanting to spend that plus another $100 to get a mechanic to put it in for me, I thought it might be worth just cleaning the thing. The TPS is essentially a potentiometer and being an electronics guy I know all about those and how they can behave erratically when they get a little bit of dirt or corrosion in them. Or it could even be the connector, dirt in there would certainly mess up the signal.
So the first thing to try is simply cleaning the connector. Before I did that, I had to locate the TPS. It sits on the throttle body on the opposite side from the throttle cable, it just looks like a small black box with some wires connected to it.
To remove the connector, squeeze the release catch while pulling.
I sprayed some contact cleaner in it and blew it out with some compressed air (not having a compressor, that means just blowing into it really hard and having the contact cleaner spray back into my face).
I reconnected the plug and went for a test drive. The car was much smoother. Problem solved in five minutes (if you don’t count the hours of research to figure out what to fix).
I’d call that a win!