Hey, guys.. Just signed up and was hoping some kind soul could help me get a 2002 Neon ES SOHC 16 valve going again.

Here's a little history on the situation:

Timing belt snapped on the road and bent 4 valves. Removed head, replaced bad ones and lapped all 16 (replaced stem seals also). Tested for valve seat leakage (poured gas in all exhaust/intake ports) and barely a weep from any. Cleaned head and block surfaces, tossed head back on with a new gasket and spark plugs. Lined up the cam and crank pulley arrows dead-on and plugged back in all sensors. Cranked engine but no spark. Re-checked connections and found I accidentally plugged cam position connector into coil pack and vice-versa. Corrected that, and got a lot of sneezes/farts out the intake and exhaust (backfiring) when cranking.

I scanned ECU, got (pending) code p0340 (cam sensor) only. Replaced it, but now am not getting spark at all (code disappeared, however). Unplugged connector to it, and get spark but with accompanying backfiring again.

I checked cam sprocket dowel pin and it was intact and re-confirmed timing marks are aligned. I'm wondering if there's a problem with the crank sensor or PCM, but there weren't any problems with them before the timing belt mishap so I'm a little stumped as to what's up. Though I don't think this matters, I do NOT have the alternator or power steering belts connected.

Anyone have suggestions? Thanks in advance.

 

if you try running the car without the alt hooked up you're going to kill the battery. i would have everything connected for s&g's. did you disconnect the battery before doing anything sensor wise? other than that, i have no suggestions lol. sorry.

 

Yea, I disconnected the battery before working on things. I didn't want to reconnect the accessories just in case I had to take the head off again or something.

 

Are you sure the timing isn't 180° backwards/forwards?

 

Thanks for replying. Do you mean do I have the cam sprocket on backwards? The way it's on is with the timing mark(s) facing outward (in order to align it with belt cover arrow), so I imagine it's on correctly. Doubt there'd be marks on the opposite side.

 

It may not be 180° out (I guess it really can't be without a distributor), but usually a backfire with no start is a timing issue. Just to double check, after you installed the crank sprocket to TDC, you backed it off 3 notches? Then you set the cam to TDC? Then you moved the crank forward to 1/2 mark before TDC before installing the belt, then to TDC after installing the belt? And after all of that, you rotated the crank two times ending on TDC to verify alignment?

EDIT: Missed the part about you confirming the timing marks are aligned. You never rotated the crank counter-clockwise did you? To have a backfire out of the intake, an intake valve has to be open during ignition, which means something is off somewhere. Even more so I'd think if you are getting a backfire out of the exhaust at the same time.

 

I'm only getting backfires when the cam sensor's unplugged from its connector. When its plugged in, not getting any spark at all (thus no backfiring).

Not sure what you mean by if I rotated the crank counterclockwise.....

 

I mean that when you turned it to get it to TDC. You are only supposed to turn it clockwise. Anyways...I'll have to think about it.

 

I talked to a mechanic over at the local Dodge dealership and his hunch was that the PCM got damaged when I mistakenly swapped the sensor plugs. He actually said someone in the shop did the same thing once on a similar motor and that's what ended up happning.

Guess I'll be heading up to the junkyard to grab a few to see if it works.

 

A far-fetched fix unless something shorted, but it does happen.