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Fresh rebuild engine wont run


Old 12-08-2017, 12:28 AM
John_jenn is offline
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Default Fresh rebuild engine wont run

Need some ideas for my 2005 dodge neon sxt 2.0
had engine rebuilt put it all together ran for 19 miles then suddenly died, threw bunch of random codes, wish i wrote them down but since i was stuck in the middle of traffic i cleared them to reset ecm and attempt to drive at least into a parking lot. I do know it threw cam sensor error p0340, barometric pressure, o2 sensor p2096. after resetting kept throwing cam sensor error and would not turn over at all just dry cranking with occasional sputter.
I found a shorted wire on the speed sensor, rewired that plug and replace speed sensor and cam sensor, no codes when started but lacks power stalls when put into gear. all four plugs badly fouled after 19 miles. number four coated heavily in black soot. had to tow it home.
there i replaced crank sensor, did a compression test 170 psi all cylinders does build over several strokes starts at 120ish, sent ecm in for testing. tested fine. put it back in went through wiring again, replaced cam sensor with another brand. started it with air filter housing open and filter out there i found when it stall exhaust smoke comes billowing out of the intake so its backfiring into intake when it stumble the stall at idle. from there i replaced throttle position sensor (TPS).

So Right now with new TPS it will start runs better then with old one, still stalls at idle, i can hear it backfire into intake when it stalls. I can now start it and rev it up with the gas pedal it will hold about 2000 rpm with occasional sputter hesitant to rev up, hitting gas pedal quickly falls flat. will not maintain idle for long, before changing tps would not idle for more than 15 seconds before stalling, now will idle for 30 second to a minute sputtering and backfiring until a bad backfire stalls it.

Plugs were very fouled so i cleaned the ones before the rebuild and put those back in. I also attempted to check fuel pressure but fuel rail does not have a port to test so testing fuel pressure would require cutting a line to splice in tester unless i missed something.
I think ill get some new plugs since it is very cold here and they were badly fouled before i cleaned them. any other thoughts cause im at a wall and ready to scrap this thing but already spent so much having it rebuilt.

History, had a blown head gasket rust in piston sleeves, pulled engine and had it rebuilt by a local machine shop.<br />Previous owner replaced ecm, cam sensor, coil pack, wires and plugs, crank sensor and could not get it to run since timing belt was loose and head gasket shot.
I replaced top end o2 sensor, map sensor, fuel injectors with rebuilt ones, speed sensor, cam sensor with two different brands crank sensor again, throttle position sensor, fresh plugs with rebuild and timing belt, water pump, fuel filter/regulator.
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Old 12-10-2017, 02:57 AM
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fca tech
fca tech is offline
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did you check the timing belt to see if it has jumped also there is a magnet on the back of the cam shaft where the sensor is mounted I remember reading a Chrysler article years ago that they can come loose I never seen one myself thou backfiring thru the intake is a sign of ignition timing off since its controlled by the pcm and cam and crank sensors I would look at the timing belt this is some diagnostics out of the service manual and a copy of the timing marksENGINE STALLS OR IDLES ROUGH1. Idle speed too low.1. Test minimum air flow. (Refer to Appropriate Diagnostic Information)2. Incorrect fuel mixture.2. (Refer to Appropriate Diagnostic Information)3. Intake manifold leakage.3. Inspect intake manifold, manifold gasket, and vacuum hoses.4. Faulty ignition coil(s).4. Test and replace as necessary. (Refer to Appropriate Diagnostic Information) keep in mind if the timing belt did jump this is a interference engine and could result in bent valves
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Old 12-14-2017, 01:22 AM
John_jenn is offline
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installed the timing belt myself after rebuild, checked rechecked and checked again to make sure alignment and tensioner pulley were good then cranked engine several time by hand and checked timing again and again before installing, problem with checking timing now means at min pulling harmonic balancer to access timing belt fully now means removing front engine mount and lowering engine enough to access timing cover.
I have read oem cam sensors wont work must be mopar part i have a hard time believing two different brands of aftermarket sensors would function in the same manner having same exact problem. cam sensor magnet looked ok when sensor was off, not loose or damaged visibly. I also heard rumors magnet losing the magnetism?
Fixxed all intake leaks and vacuum leaks when reassembling unless theres a problem with the vapor canister.
Ignition coil was replaced before rebuild.
fuel pressure untested.
So lets say im confident theres no problem with the rebuilt engine must be a fault with the electrical side or fuel delivery, pcm tested ok, cam and cranks sensors new oem sensors, coil pack new before rebuild, map replaced before rebuild, tps replaced improved symptoms somewhat, injectors replaced before rebuild, fuel filter/regulator replaced before rebuild cheap oem.
Am i missing any other sensors that could cause pcm to fire in the wrong timing? or maybe another short somewhere?
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