Acceleration Troubles after Serpentine Belt Replacement

  • This is my wife’s car before we were married so I don’t have much history with the car. 2009 Mercury Milan 4 cyl 2.3l
  • Sepantine belt snapped (had slipped of 2 times prior)
  • Jacked up front end (was raised 3 days while slowly working on it)
  • Opened passenger side wheel well and removed broken belt - was twisted up pretty good
  • Removed belt tension pulley assembly
    Sprayed degreaser on passenger side of engine block, scrubbed all pulleys and wiped with towel. Rinsed with water from spray bottle, wiped with rag. It was very dirty
  • Installed new tension pulley assembly and routed new belt.
  • Started engine and turned over fine, everything seemed to be working.
  • Put back wheel well housing and wheel lowered car off jack.
  • Started car and again started fine.
  • Put in drive and it gets into gear but cannot accelerate, stepping on throttle slightly decreases RPM and may die after starting or just roughly idles until back in park or neutral
  • Car will go into reverse okay. But still no acceleration
  • When in park or neutral I can step on throttle and rpm will go up to 2500 but cap there.
  • Check engine light is NOT lit
  • OBD2 sensor shows no error codes
  • I tried to pull up different graphs with the OBD2 and one was the fuel pressure which read at 0, not sure if that is just a fluke with the cheap tool I have.
  • I also noticed that sometimes the brakes get harder to push
  • Seems like there are some engine pressure issues as I can open the oil cap and there is positive pressure coming from the opening
  • Before replacing the belt the car ran fine.

You didn’t by chance knock a vacuum line loose did you?

I really doubt an 09 has a sensor for fuel pressure, which would be why your OBD2 reader doesn’t show any pressure

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Where was car when belt snapped? In driveway?
On highway? 1 mile from home?

I was backing out of the garage.

I don’t see any loose hoses and everything thing seems to be intact.

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Almost sounds like e-brake issue. Reverse is ok but no forward

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In the old days I would say the PCM has gone silly. I don’t believe the problem is belt related because you probably checked for freedom of pulley motion. (Great use of English) Rebooting the computer by disconnecting the battery isn’t a good idea these days either. If your car is worth under $2000… Stop reading this now and stay competent.