222k miles motor swap for 56k motor swap in kids first car!

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222k miles motor swap for 56k motor swap in kids first car!

Post by SolCalSpark » Wed Jun 18, 2014 2:35 am

We bought my son Noah his first car a 2003 Dodge Neon SE w/222k miles. CEL light on and throwing the following codes p300, 302,303, 340, 344 and 1604. Test drove the car and it shook violently til up to speed and drove fine on the freeway the 30miles to get her home.
Got her home and found cylinders 3 & 4 dead, blown head gasket.

Found a 2004 SE motor w/56k miles for $440 and threw her in over the weekend. Swap went relatively smooth minus the retaining nub breaking off the high pressure switch on the back of the a/c compressor ! Drat !! I've got connections so it won't cost me more than the price of the switch. Just hope the zip tie holds the connection through summer !?
So the big day !!! New Motor cranks but won't start. Wan wah waah ! No codes present.

Check ignition : 3 of 4 plugs and wires w/carbon tracks, R&R plugs and wires. Fires up but runs like crap. Violent idle til stalling out.
Check ignition : inline spark tester shows good spark on all cylinders. Coil and wires good, plugs 1 & 2 covered with soot, plugs 3 & 4 still look brand new...
Check compression : 125 psi on all cylinders cold motor.
Injector noid test : injectors 1 & 4 tested and both react at same pulse rate.
Fuel pressure test : 53 psi w/ key in start position at idle and in Drive w/ foot on brake and 1/4 throttle input.
Car starts up now and idles smoother than before but quickly deteriorates back to idling like crap and stalling.
And finally it's throwing code p0171 system to lean bank 1.
No shit !
Next test : unplug upstream o2 sensor, pull - battery cable to reset ECM. O2 sensor is the one that came with the new motor.

Deductive reasoning is telling me that it's something other than the motors and rather something attached to it. Which leaves the downstream o2 sensor, plugged cat/exhaust, ECM and all the fuel sensors.

Anyone with insight into this mystery would be appreciated !
Why are cylinders 1 & 2 running rich and 3 & 4 running lean ??? My gut and 20+ years of working on cars point me to the ECM but I've been wrong more than a few times with this car.
Don't like throwing parts at a problem and hope it works !!!


Jeff n Noah

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Post by r/tguy02 » Wed Jun 18, 2014 8:27 am

i'd replace the upstream o2, check again

fuel pressure should be 58 but 53 isnt far off

i'd also check the wiring to the o2 sensor for short

its not common for the ECU to fail so i would look elsewhere first.
[02 R/T sold][00 Highline sold][04 r/t scrapped][95 NYG Sport coupe][01 r/t DD]

occasional demons
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Post by occasional demons » Wed Jun 18, 2014 10:40 am

Which injectors did you use, the ones from the original engine, or the ones from the replacement engine? If the replacement engine has sat for a while, those injectors may be clogged or gunked up, either way could dump too much fuel, or not enough.

Try swapping the injector set, if the 2004's and see what happens with the lean code. 3 & 4 may be plugged enough that 1 & 2 are dumping fuel trying to compensate.

The PCM only sees a lean condition, so it is widening the pulse width on all the injectors, if two aren't responding, it has no way to know.

Edit: Swap over the entire fuel rail. Could be debris in there too.
dblsg wrote:ya'll a bunch of post whores

2001 Neon ES MTX with '02 R/T PCM
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!!! Success !!!

Post by SolCalSpark » Thu Jun 19, 2014 2:01 pm

Annnd we have a winner...

DRUM ROLL... Please

The winner is occasional demons !!!

Success :D TYVM OD !!!

I swapped the old injector rail onto the newer motor and Voila !!!
Going to see what I can do to clean the newer set with a injector pulse tool set tomorrow...
Still can't figure how to upload pics from dropbox of the kid and his new neon to post here ???

Thx Jeff


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