or not properly torqued to spec.......happened to me on an old pickup I once had.....rebuilt the motor, painted the block, screwed the knock sensors into the painted holes.....engine would run fine for days and the all of a sudden , seemingly for no reason at all run like crap. the knock sensors werent grounded to the block properly.... is it possible that a newer vehicle with OBDII could TRY to compensate , and "seem" to run fine but register the issue as a misfire ?

 

the difference is yours was actually running like crap - which makes sense as the ECU was changing ignition timing for non-existant knock events.

misfire detection is almost always done with rate of change on crank teeth.

he's got a crank sensor issue...

 

Well I ordered a new CKP for 33$ (SMP PC714 from RockAuto). If it fixes it, great. If not, I have a cheap spare.

 

ET - in the pix, the outer ring with teeth is what the starter engages (you know dat, but newbi might not). The inner ring with the milled gaps is what the CKP uses to make the signal. When you had the block out to go to the shop, was this removed and perhaps not put back in alignment? It has a gap in those teeth that provides the sync to the ECU. There are 60 of these "teeth" and they are 6 degrees apart. There is a missing gap that lines up with 60 degrees before top dead center of cylinder number 1.

 

EXACTLY !!!

all some of us are doing is trying to help this guy figure out his issue, It has been widely reported here on this forum & others that a faulty crank sensor usually leaves you stranded...no spark at all. At this point it seems that the crank sensor is doing its job....relaying the message to the ECU....don't be so quick to shoot the "messenger"... until he figures this thing out.

 

I am lost on this. This one had so many problems when you first got it, you have no real baseline do you to know what existed from before rebuild that you have not yet stumbled upon.

 

Hmmm... The hub aligner is dowel located on the crank shaft so that can't be misaligned, but I can't remember or find if the ring gear is also dowel located on the hub aligner. Since there are 4 bolts securing the ring gear to hub aligner, it could be off 90 degrees. To check, I could move cyl 1 to TDC and I guess the gap should be 10 tabs before the CKP. If it really is off 90 degrees then maybe these are the symptoms? Really don't want to take the engine out again...

 

if you were 90 degrees off my guess would be the engine wouldnt run well, if at all.
it uses that missing tooth to determine the ignition timing as everything is based off of degrees away from TDC.


i would start looking at the sensor mounting, the sensor condition, the wiring/sheilding conditon to the sensor, sensor mounting, etc... and ideally (if you can get your hands on one) throw an o-scope on the sensor output to see the waveform. this will be the bottom line. if it scopes out ok, then youve got something else going on (which could include issues with the VR conditioning circuit in the ECU itself...)
my guess is that it wont look very smooth though, and that your issue is related to the sensor. also check sensor gap, or see if for some reason its sitting too far away from the trigger wheel - ive seen this happen if the sensor is oring sealed and the wrong oring is used or the oring moves during install.

im assuming (without having looked at it) that its a 2 wire sensor


the waveform will look like the one on the right of that picture... with a long "gap" where the missing tooth is.
the ecu uses the 0 volt crossing point to determine the tooth position. if the signal is noisy or inverted, the 0 crossing occurs at the wrong position... which will confuse the rate of change function that is monitoring tooth position to determine misfires.

 

Like we said, reverse the wires from the sensor and you'll be off 3 degrees on timing, it uses one edge as the trigger, not the center of the waveform.

 

Eric, take some more pics when you ar in there please. We are all learning a lot with you on this rebuild.

Just finding an oscope this days could be a challenge.

Good Luck with it.

Have you looked at the inside of your ECU yet? I am just wondering if there is aproblem internal to the ECU.