Hello everyone, I recently replaced the motor in my stratus with a used one from a junkyard, it runs good expect it won't stay running unless I have my foot on the gas a little bit and runs really rough.

Already replaced the IAC and MAP sensor and the upstream O2 sensor. It will run alright at higher RPMs with a little misfiring sometimes. Did a PCM reset and cleaned out the TB really well. If I unplug the IAC and try starting it, it won't even fire at all, so That seems to be working letting air in. Also to get to higher RPMs you have to do it slowly, if you gas it too fast it will just stall out.

Anyone have any input on this issue? My next guess is a weak coil pack maybe, the wires were a little wet when I started it first and maybe shorted out the coil pack a little. I'll head to the junkyard Monday and see if one from an older neon fits just to test it out. Fuel pump sounds a little weak so I'll replace that too from a 02 Sebring sedan v6 while I'm at it, but I don't think that's an issue, I'll report back with a fuel rail pressure reading once I find it out.

If anyone needs anymore information, just ask. Thanks.

 

What year was the motor you just installed?

 

Thanks for the reply. The motor I got was from the same year and model, I believe it was a 1 year fit with all the variations in the 2.4.

I replaced the PCV valve and it doesn't stall as often now, also did all new spark plugs which didn't make a difference. Recently I lost all throttle response and it will idle high at 2K RPMs, so I'll get the TPS replaced soon.
At my local junkyard I have access to at least 10 neons with a 2.0, 5 sebring sedans all with a 2.7, and a few 1st gen stratus with a 2.5 motor though. So I'm trying to find interchange parts between the different engines just for testing, since I can get parts there dirt cheap, then buy the new correct sensor once I isolated the problem.

Another possiblity could be a clogged exhaust, it has a cracked runner on the exhaust manifold for cylinder #1, which happened on my old one as well as the one that came with the other used motor, also there's 4 bolts connecting the exhaust pipe from the cat to the end of the manifold, 2 of the bottom bolts rusted good and broke off so it's not perfectly sealed and there's exhaust smoke and a lot of low noise coming from the area.

 

Well I pulled the exhaust off and found the cat was rattling pretty good so I gutted it (shh don't tell Al Gore) I ordered a new one, but it didn't fix anything running it open.

So anyways when this started happening I went on ebay and bought an ELM ODB to USB thing from China for like $12 for my laptop and just got it today. Now I think I got this problem nipped in the bud reading the interesting information the sensors were putting out.

With the engine off (the car won't run for more than a second, it will drop to low RPMs untill it knocks itself dead) I read data from all the sensors and it has both intake air charge and coolant showing me 59F which is seems about right (the coolant probably all settled below the sensor) The O2 sensor was showing about 1.27 volts. But the 2 things that didn't make sense were the throttle position percentage and the map sensor reading. First with the throttle closed it was showing it 15.4% open and with the pedal to the floor it showed me it was 77.3% open. The map sensor (with the engine off and opening and closing the throttse to equalize the air pressure inside) was showing me 50.4kPa or about 7.2 PSI.
Voltage on the TPS when connected to it's wiring harness (this I checked manually with a voltmeter) was 0.73v closed and only 3.74v at WOT, I heard from some people this is normal and some say it's suppose to be 0.2v to 4.8v.

If anyone can make sense of that, that would be great, I'm no expert but I think I need to replace the MAP and TPS.