MAP (manifold absolute pressure) sensor issues P0108

Discussion in 'Modifications And Maintenance' started by pbedroske, Dec 6, 2017.

  1. pbedroske
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    pbedroske Well-Known Member

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    Kinda long story, I'll try to keep it short but as detailed as needed.

    I pulled my engine this fall to do valve cover gaskets and other gaskets rear main seal, etc. During re-install there was an issue with spark plug wires being switched on the drivers side of the engine (rough idle, backfires). While this was fixed I also had a P0108 code for MAP sensor reading too high. I got a used MAP sensor off ebay and drove for while. (meanwhile my radiator sprung a leak and I'm waiting for replacement). However, the P0108 returned while idling back to the garage to wait for the new radiator. I used a scan tool to monitor the MAP. Most of the time it seems to be reading fine (lowish ~10-12 inHg at idle), but occasionally spikes to ~75inHg for a fraction of a second - causing the CEL. I'm speculating but seems to me to be a short to 5V. Perhaps a bad connector. I could try using the old MAP sensor and see if the issue remains or use another known working MAP sensor to rule that out.

    Any other ideas to fix this????
     
  2. pbedroske
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    pbedroske Well-Known Member

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    This is in regards to a 2004 WRX ej20 with VF39 and accompanying mods, custom tune (Bullwinkle)
     
  3. pbedroske
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    pbedroske Well-Known Member

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    Finally got the radiator installed and took my car to work today. No issues as far as I could tell on the way in to work. However, after work when I started it, the CEL was on. Checked and again it was P0108. I monitored the MAP which seemed fine for a while, then just oddly off... normal MAP should be around 29 inHg at 0PSI, but this was jumping up to 55-65 and sometimes full 75.3inHg at vacuum. I stopped at Walmart, got some things then the CEL was off when I restarted. I monitored again and it started off fine, but after a few miles it was almost steady at 75.3inHg and had a rough and very low idle. I did some "diagnostics" at home after it cooled down. 5V seems dead on Key on engine off. ground is fine. signal is around 0.67V. I cleaned the contacts and added some dielectric grease. If i ran the car with the sensor unplugged it registers the 75.3inHg, and plugging it back in its back where it should be around 10-16inHg. I checked for vacuum leaks with propane and couldn't find any. all grounds look good. all connections look good. the TGV sensor and motor wires are still wrapped up and not contacting anything (fearing a 5V short to ground)..
    We'll see what happens tomorrow...
     
  4. pbedroske
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    pbedroske Well-Known Member

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    Car was a no-go this morning. Had to take the Vibe into work with no working radio. CEL included P0122 (TPS low) P0107 (MAP low) and P0108 (MAP high). On to dissecting wiring harness...
     
  5. pbedroske
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    pbedroske Well-Known Member

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    Well, fixed it. loose F61 connector by the battery SMH. I don't know if I should feel good about fixing it or bad that I missed it back in September when putting the engine back in...
    Meanwhile, the family Acadia had to get towed in for misfires on all odd cylinders 1, 3 and 5...
     
  6. tangledupinblu
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    tangledupinblu Event Coordinator Staff Member

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    Man, crap luck! Glad that you solved one of the problems and it was a cheap fix!
     

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