New rebuild now idle problems...

[mike1999]

So i just got my engine rebuilt bored .020 over lower compression and everything if that matters and i am having idle troubles. The car starts fine but it has a hard time staying at idle, sometimes stalls and when the rpms drop quickly like when letting off the throttle it will stall. When the rpms are over 1500 rpms it runs fine. I am fairly sure the timing is correct for this isnt the first time ive done it and it was dead on before, i replaced the iac motor, tomorrow i am getting tps sensor and replacing that, the compression is perfect, and im getting a good spark to all of the plugs. I am wondering if the tps isnt the issue could the issue possibly be the crankshaft position sensor? I had the sensor out and the crank shaft was balanced in the rebuild process.... maybe that messed with that part of the crankshaft that the sensor reads from. Another possability is that a major ground wire was not connected the first time i ran the car, i somehow missed only that wire when reconnecting everything, so maybe that fried the pcm? Any help would be appreciated thanks!

 

[absolute_DSM]

Are you talking about your N/T? If so are you using MegaSquirt? If yes to that, then you should check out the 420a section and read up. I remember seeing a thread short time ago about off throttle tuning.

 

[mike1999]

i am not using megasquirt but i just found a post on here that referred to the engine code i am getting which i should have mentioned im sorry... 1390 which according to auto zone was an ignition problem or a misfire but i found on here that it is due to timing slipping one tooth or more so basically i am pretty excitited that i may have found the answer! so i am going to re do the timing that i was so sure of before and see if that helps... haha thanks for the reply absolute

 

[absolute_DSM]

No problem, Im happy for ya.

When you redo that timing, it might be a good idea to check the compression afterwards to make sure there was no valve contact.