Subaru Throttle Position Sensor

tomhall

Member
Joined
Apr 27, 2004
Messages
211
Location
Rochester, MN
Total Flight Time
200
Tom in MN here, I have 200 hrs. on RAF 2000 with the 2.5 FI Subaru. The engine has purred during the past 11 years. Problem : The RAF sat idle during the winter for 4 months ( nothing unusual, same for 11 years ). During an extended taxi prior to our " first flight " the engine ran rough, coughed and sputtered at RPM's between 1,500 & 2,000. Yesterday I drained half of the gas; same symptoms. Another EAA member had a " code reader " with a smart phone app. It was amazing the different data shown on that phone : RPM's, water temp., air intake temp., " miles per gallon " etc. There smoking gun seems to the Throttle Position Sensor. It's readout showed 3 % at 2,000 RPM's and other percents that made no sense. So, I will replace the sensor and hope that's the fix. Question; anyone else have experience with the symptoms and/or the sensor ? Thanks, Tom Hall in MN
 
Hi Tom.
I spent 20 years on the line as a Ford Driveability Master Technician. It sounds to me like you've made a good choice. In the past, people would get code readers and start replacing components based on the trouble code rather than finding the root cause of the code. In this case, with the newer reader (I have the smart phone app too), you were able to monitor the suspect system and verify the sensor is generating erroneous signals. I believe replacing the TP sensor in this case is the right choice.
 
Still Searching

Still Searching

Spent 3 hrs. yesterday with a smart friend working on the engine problem. We did change the Throttle Position Sensor ( seeming the likely culprit ) no change. The symptom is : Runs smooth from a cold start until about 150 degrees water temp; then it runs rough, coughs, sputters etc. between 1,500 and 2,000 RPM. Seems to run fine at 2,000 and above ? We pulled off the Idle Air Control; didn't see anything amiss ( not sure what to look for there ). Anyone had a similar situation ? I will look for a general Subaru Forum as well. Again, it's the 2.5 FI , a 2002 vintage. Thanks in advance for any help. Tom Hall in MN
 
I had a similar issue with my 2001 ej25 sohc engine. My issue went away after I put more shielding on the crank and cam position sensor wires.
 
My EJ22 suddenly started coffing and popping..... I knew it was electrical, so I changed the leads.... better but no cigar.... so I changed the coils.... bingo !!! smooth as a baby's bottom now :yo:
 
Tom in MN here, I have 200 hrs. on RAF 2000 with the 2.5 FI Subaru. The engine has purred during the past 11 years. Problem : The RAF sat idle during the winter for 4 months ( nothing unusual, same for 11 years ). During an extended taxi prior to our " first flight " the engine ran rough, coughed and sputtered at RPM's between 1,500 & 2,000. Yesterday I drained half of the gas; same symptoms. Another EAA member had a " code reader " with a smart phone app. It was amazing the different data shown on that phone : RPM's, water temp., air intake temp., " miles per gallon " etc. There smoking gun seems to the Throttle Position Sensor. It's readout showed 3 % at 2,000 RPM's and other percents that made no sense. So, I will replace the sensor and hope that's the fix. Question; anyone else have experience with the symptoms and/or the sensor ? Thanks, Tom Hall in MN

I had injectors gum up on one side of an ej 22. Just tapped the injectors while engine running and solved the problem. Another one had been left several years and all injectors had to be cleaned.

Aussie Paul. :)
 
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I would also recommend draining all of the gas (put it in your car) and fill with fresh.... todays fuel is junk.... who knows what crap they give us.... not to mention, if a tanker has just been before you get to the gas station and all of the crud and water has just been disturbed and is now circulating in the underground tanks..... and your pump is the lucky one to get a belly full of god knows what.....

I have never heard of a gas station cleaning its tanks? Have you? I just try to get fuel from large gas stations where the turnover is high.... my hope is that the more tankers, more often, the fuel is hopefully fresher and less gunk in it.... maybe.

They say the storage/shelf life of gas these days is 2 weeks.... because gas stations don't clean out their tanks, some of the fuel in there may be months old? (or longer) Use a Mr Funnel or screened funnel at the gas station if filling your machine on the way to the airport.... takes longer, but you can see if there is any water or crud going in..... otherwise use Gerry cans and a screened funnel when you fill at the airport. I have heard of a lot of people filling boat tanks at gas stations having trouble with garbage gas and filling the boat directly at the gas station....

I always run a little 'injector cleaner' in my fuel.... supposed to stop crud sticking... one may hope :yo:

Drain and flush your fuel system, change the coils and leads
 
I agree about the bad gas. When my helicopter had about 30 hours on it I decided to try some 93 octane gas instead of the 87 that I had been using to see if it would give me more power. I put 5 gallons of 93 on top of about 1 gallon of 87, I was still only doing hovering practice so I never kept more than about 5 gallons at a time in my tank. I tried to take off and I didn't even have enough power to get off the ground much less hover. I tried octane boosters, changed plugs, checked timing and cleaned air filters but nothing seemed to work. I finally messed around long enough that I burnt all 5 gallons just sitting on the ground trying different things to get more power. I went back to the station got 5 gallons of 87 put it in the tanks and it acted like I put a new motor in it, as soon as I pulled pitch I came right off the ground.
My theory was that the 93 octane was so expensive that no one was buying it so it just sat underground in the tanks for who knows how long. I have been flying for almost 4 years now and 150 hours and have not put another drop of anything other than 87 octane with no more issues like that. I do use Stabil marine grade ethanol fuel stabilizer 1 ounce per 5 gallons because the helicopter may not be moved for a couple weeks at a time.
 
Gas stations annoy me.... here in Oz, I have a friend works in a gas station on the night shift..... when he sees that the cost of gas is going to go up at 7:00am the next day, he lets me know and I go fill up.... it can go up 10c per liter (38c per gallon to you) from 6:59am to 7:00am.... the $30,000 worth of gas in their tanks is suddenly.... instantly worth $36,000..... nothing has changed? same exact fuel.... no tanker there putting new fuel into empty tanks.... they just up the price? What a rip off? Not to mention all of those problems with water in the tanks, gunk in the tanks.... who knows what octane or how long some of it has been in there? We have E89 (10% ethanol), 91 ULP, 95 ULP and 98 ULP (and some Shell gas stations have 100) but evidently 91 is often out of date 98 (which is 95 with some additives) and when 98 goes out of date (2 weeks) it goes back to 95.... out of date 95, any gas that isn't quite up to standard or failed to reach the desired octane.... simply gets labled 91 and shoved in the 91 tank :noidea:

They never clean the tanks, the filters in the hose to the car are usually not in place (they block too often) so we just have to accept poop gas....the 91 might actually be 96 one week and 90 the next? who knows?

We just have to bend over and pay for whatever they give us and hope for the best.... I just think it sucks bigtime that a commodity can increase its value just because of some 'cycle' in gas production....???

As usual, we just have to pay up and shut up!

Is it the same in the states? Or the UK (Steve?)

end of rant... sorry :lol:
 
YES it is about the same
 
Still Searching

Still Searching

So, I replaced the Throttle Position Sensor, the Fuel Pressure Regulator and put in new plugs and plug wires ( NGK ) .................same symptom ( after coming to about 140 degrees, runs rough between 1,500 and 2,000 rpm; seems to be a bit better with the Aux. fuel pump on ? The next " smoking" gun is the primary fuel pump. I hate fixing' blind; without a real diagnosis. If nothing else I am eliminating some suspects. Any more thoughts ? Thanks Again Tom Hall in MN
 
Tomhall,
You might want to post your questions on the FlySoob group on Yahoo. Some of the people there are fairly knowledgeable an might offer some additional expertise.

Worth a try, but may take a few days as you have to register and be 'approved'.

Mi dos centavos.
Chris
 
Sorry to nag.... change your coils.... and where the 4 bolts that hold the pair of coils down, clean the contact patches with sand paper for a good earth. Also, make sure the engine block has a good earth (its own wire) to the battery earth. The difference the changing of the coils made to me EJ22 was astonishing.... instant fix, made a sick puppy purr like a kitten in a milk factory :yo: and cheap too :lol:

Edit: Remember on the sooby, the coils are 'buddy spark' so there is 2 coils for 4 cylinders, the plugs spark on TDC on the power stroke and on the other cylinder (for that coil) on its exhaust stroke.... so if one of the coils becomes intermittent or fails, it affects 2 cylinders. I find intermittent or dead coils with a timing light that clips onto the spark plug lead.... I don't point the timing light at anything, I just watch the flashing.... if it is not fast and regular, that coil needs changing. I put bolb grease on the end of the lead before pushing it onto the coil, to keep good contact and stop that white powder happening under the rubber boot. They are the same coils and setup on the EJ25 :yo:
 

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Thanks Guys, I will do the coils and I am glad to hear about the Flysoob group. I will again report on any progress. Tom T. in MN
 
The Hunt Continues

The Hunt Continues

Put on the new coil.............no fix. I will now replace the primary fuel pump, If that doesn't solve the problem, I will try to find a smart Subaru mechanic to come to the airport and hold my hand. More later. Tom
 
Problem resolved ! !

Problem resolved ! !

After multiple organ transplants, I was searching for a local Subaru mechanic.......I found a web-site " Just Ask ". It said 2 Subaru mechanics were ready and willing. I stated my case and paid my $ 26. " Matt " ( with 35 years experience ) said " sounds like and air leak ". He guided me through the process. Bottom line : I removed and replaced the " Air By-Pass Hoses " that go from the intake manifold on one side, then " T " up to the Air Assist Injector Solenoid Valve, then continue on to the other intake manifold. There were some small cracks on the ends of the removed hoses. I had always idled at about 1,350 RPM; now I idle at about 850 RPM ! ! I taxied for longer that normal without " Murphy's " presence. About that same time my hydraulic brakes started spewing red liquid.......... but that's another story. Thanks for listening and your support. Tom T. Hall in MN
 
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