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Discussion Starter · #1 ·
Recently bought an 04 SRT4 Neon with 13600 miles. No crank, no start, red security light when I bought it. Took it to Larson Dodge, they replaced the pcm, car starts now but idles extremely rough and choppy and won’t pass 1500 rpm at WOT. Smells like fuel from the exhaust. The car also keeps running after the key is removed. The only code showing is P0112. As far as I know, the car has a Godspeed fmic, agp wastegate, short ram intake, greddy BOV, and a Diablo I2 (don’t know if any tune was installed with old pcm and can’t communicate with new pcm). The previous owner also replaced the MAP, cam sensor and magnet, and installed an MSD coil pack trying to get it to run and I replaced the plugs as they were caked in carbon and covered in unburnt fuel. Any help would be appreciated.
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P0112 generally means a bad sensor, or the wire got cut or shorted. AGP and Modern both have them, I think Modern sells AGP's, but I'm not sure.

Check the wire running to the sensor, if it is broke or the insulation is rubbed off, you can solder it together and put insulated shrink wrap or electrical tape on it. If it is broke right ON the sensor, you likely need a new sensor.

That being said, that shouldn't be causing issues as extreme as you are describing.

Aftermarket coil packets seem to really be hit and miss, that may be an issue right there. Sounds as though you most certainly need a new ignition switch, no way should you trust it with the car continuing to run after you pull the key out. As far as not revving past 1500, could potentially be a fuel pump/fuel filter/fpr issue, they are all on the fuel pump housing together, inside the tank. Bit of a pain in the butt to replace. There's other stuff I'd check first but I'll let some others weigh in also.
 

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Discussion Starter · #3 ·
P0112 generally means a bad sensor, or the wire got cut or shorted. AGP and Modern both have them, I think Modern sells AGP's, but I'm not sure.

Check the wire running to the sensor, if it is broke or the insulation is rubbed off, you can solder it together and put insulated shrink wrap or electrical tape on it. If it is broke right ON the sensor, you likely need a new sensor.

That being said, that shouldn't be causing issues as extreme as you are describing.

Aftermarket coil packets seem to really be hit and miss, that may be an issue right there. Sounds as though you most certainly need a new ignition switch, no way should you trust it with the car continuing to run after you pull the key out. As far as not revving past 1500, could potentially be a fuel pump/fuel filter/fpr issue, they are all on the fuel pump housing together, inside the tank. Bit of a pain in the butt to replace. There's other stuff I'd check first but I'll let some others weigh in also.
 

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Discussion Starter · #4 ·
I just swapped the old coilpack back in and it’s still running exactly the same. Also has some pretty gnarly belt squeal, which could just be a pulley, and vacuum bounces from 9-11 at idle
 

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Discussion Starter · #5 ·
Update:
I put the oem TPS back in the car. It seems as though the spring loaded clip inside the throttle body was not in the right position. Now the car runs a lot smoother, but has absolutely 0 throttle response. Idles for a minute, then starts bogging and dies. Now throwing code p0122. Still smells like unburnt fuel. Vacuum now sits at 0, where as before it bounced around 10
 

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It is really hard to say, I don't have a lot of experience with troubleshooting something like this because I've been VERY blessed with my car to avoid any engine problems. Transmission, that's another story. You would potentially get ahold of a DSP or have someone local familiar with doing a datalog. Have you run a vacuum/boost leak check? May potentially be an intake/exhaust manifold leak also. Another potential thought is the O2 sensor. It will honestly feel like chasing ghosts until you find the right issue, unfortunately.
 

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Discussion Starter · #7 ·
It is really hard to say, I don't have a lot of experience with troubleshooting something like this because I've been VERY blessed with my car to avoid any engine problems. Transmission, that's another story. You would potentially get ahold of a DSP or have someone local familiar with doing a datalog. Have you run a vacuum/boost leak check? May potentially be an intake/exhaust manifold leak also. Another potential thought is the O2 sensor. It will honestly feel like chasing ghosts until you find the right issue, unfortunately.
I actually replaced the upstream o2 sensor last night. The idle smoother out a lot, vacuum sits at about 15 now, and revs up to 2000 rpm. Still won’t go past that and boost won’t go above 0. Still need to do a vacuum leak test.
 

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I actually replaced the upstream o2 sensor last night. The idle smoother out a lot, vacuum sits at about 15 now, and revs up to 2000 rpm. Still won’t go past that and boost won’t go above 0. Still need to do a vacuum leak test.
Did you reset the PCM?
 
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