MAP sensor woes

[killjoy323232]

On the way back from getting my alignment done, I had the CEL come on. When I read the codes, I was getting the dreaded P0171 and a P2097, which I initially dismissed as a leak in the exhaust (there's a throttle-sensitive tick that I'm pretty sure is an exhaust leak).

 

When I plugged my AP in to check temps/lambda/boost and the like, the boost reading was stuck at 1 PSI at idle. I checked the MAP and baro values on the AP, and they were something ridiculous like 13 and 14 PSI (hence the 1 LB boost reading). I unplugged the MAP sensor, and the car throws a MAP CEL, but the boost/vacuum readings appear to be correct.

 

I'm pretty sure my MAP sensor is hosed (got another on the way), but does the ECU have a backup way to measure boost/vacuum? I'm just curious at this point, although I'm also curious if the P0171 is related.

Edited October 7, 2021 by killjoy323232

[Max Capacity]

https://www.google.com/search?q=P2097+-+Post+Catalyst+Fuel+Trim+System+Too+Rich+Bank+1&rlz=1C1OKWM_enUS906US906&oq=P2097+-+Post+Catalyst+Fuel+Trim+System+Too+Rich+Bank+1&aqs=chrome..69i57&sourceid=chrome&ie=UTF-8

[killjoy323232]

I read up on both the 0171 and 2097 codes...evidently I didn't read hard enough! Especially the bit about a failed MAP sensor possibly causing the code.

 

I've got another on the way. Fingers crossed.

[killjoy323232]

Well, something's officially broken. Swapped out the MAP sensor this morning, and the new one is reading extreme in the other direction (11 PSI boost...at idle).

 

It threw 2 new codes, so at this point, I'm thinking wiring somewhere might be the issue (P0068 for the MAP/throttle position correlation, and P2227 for the barometric reading being crazy, AFAIK). Once it set those 2 codes, lo and behold, the AP started reading vacuum!

 

I've got a PDF of the service manual somewhere...just don't remember where. Definitely not looking forward to this one.

 

Edit: need to do a little more digging. Apparently 14.65 PSI is normal barometric pressure for my altitude. The MAP readings, especially with the new sensor, however...

Edited October 13, 2021 by killjoy323232

[killjoy323232]

I looked under the hood on my lunch break, and took an especially close look at the MAP sensor hose...and found nearly every single vacuum/purge hose is connected wrong!!! It's a wonder the car hasn't blown up yet. There's at LEAST one massive vacuum leak from where the MAP sensor should be connected, and the FPR and recirc valve are tied together, so neither are actually doing anything. Haven't pulled the IC off, but all of this crap is getting fixed before I drive the car again.

 

They had the MAP sensor connected to one of the purge valve lines (17 and 26 are tied together). What's connected to the MAP port, you may be asking? Nothing at all. No wonder I was getting a lean code.

 

So, the codes and the MAP sensor not working are two related issues, but the MAP wiring must still be bad, since the MAP reading doesn't change when it's not connected to anything (it reads high with one sensor, and REALLY high with the other). I'm going to get the vacuum lines sorted first, then attempt to figure out what's wrong with the wiring.

Edited October 14, 2021 by killjoy323232

[killjoy323232]

Well, I'm pretty sure I've got the issue figured out. All of the important vacuum lines are looped, and all of the vacuum sources on the manifold are open to atmosphere, which as we all know, is a very bad thing. God knows how long it's been running like this, and I'm probably going to have to start budgeting for a new motor.

 

As an aside, these forums are a veritable treasure trove of information...you just have to dig for some of it .

 

Moral of the story: If you buy a super-cheap turbo Subaru from a sketchy dealership, give your vacuum lines a close look. Someone might have Ray Charles'd one/some/all of them.

[whitexc]

Fingers crossed bud. Hope you get it squared away. Keep that oil topped off too lol.

 

Sent from my SM-G996U using Tapatalk

[killjoy323232]

Alright, the car is back to...well, I wouldn't call it "factory", but as normal as it can be. I removed the alternator and the intercooler for better access, and found that the blue tee was completely gone. I just relocated the tee to the front of the engine, off of the MAP line, and left the recirc valve directly plumbed in to the rear of the manifold, so everything is hooked up, and nothing is left open or leaking! (Hopefully...that stupid rubber ring on the intercooler-to-TB connection threw me for a loop. Might have to revisit that).

 

All I can say is, man, this thing hauls now! It's still running a tiny bit on the lean side, but it's not stumbling nearly as bad as it was. I saw a peak of 15 PSI (with the appropriate AFRs) on the highway from the turbo (on Cobb's OTS STG 1), so the MAP sensor is working like it should. Might still have a tiny vacuum, or exhaust, leak. Fuel trims at idle are leaning positive (14% LTFT), but there's a tick under load, too.

Edited October 18, 2021 by killjoy323232