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Discussion Starter · #1 ·
Hey guys, I'm new, but I need some help (trying to avoid going to a mechanic and dropping a bunch of money). I have a 2004 forester, with codes p1086 and p1088, which I understand to be the TGV/TPS sensors. I have difficulty understanding why I would be getting those codes and the same time, or why both sensors would have gone bad. Symptoms include engine stalling when first starting car if I'm not giving it gas, and a very rough idle (shakes). I know there are a lot of things that could be causing these issues and I'm trying to pinpoint it. Thank you for any help.
 

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1999 A/T - 235,000 mi. WA state
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1st post - welcome

don't know the codes, but shaking at idling (does it idle at reduced rpm?) and stalling on startup suggests to me it not firing on all cylinders.
 

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Discussion Starter · #3 ·
code 1088 Tumble Generator Valve #1 Position Sensor Circuit Low Input
code 1086 Tumble Generator Valve #2 Position Sensor Circuit Low Input
I thought it could be a dirty throttle body?
 

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'21 ISM Crosstrek Limited
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The TGV motors are connected via connectors near them which are subject to environmental conditions, like water, etc. They get corroded and the TGVs stop working correctly, sometimes intermittently and sometimes totally. At least in earlier years such as yours the TGVs were a problem, often due to bad connectors.

Take all TGV connectors (actually, always consider ANY connector suspect) apart and clean both male and female contacts... contact cleaner, emory cloth, etc. Then tighten the female contacts slightly (like with a pin, or sharp tool. Spray with contact cleaner, pack with dielectric grease, and reconnect.

This solved more than one TGV problem for me. I ended up deleting them in one vehicle of similar vintage. I'm surprised they've worked for you this long. Won't hurt to try...at best it'll solve your issues and at worst will end consideration of those connectors in this or future diagnostics.

I don't think it is the throttle body, although doing the same treatment to its connectors is a good idea also.

HTH
 

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Discussion Starter · #5 ·
quick question: is once sensor a tumble generator valve, and one a throttle position sensor?
 
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