Timing issue at idle

Xenogenesis

New Member
Dec 17, 2019
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0
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19
Tennessee
It's a 3.8 V6, return style fuel injection, with an ignition control module.

When I start it up, the timing jumps to 28°, engine misfires like mad before it just bounces from 17° to 28° back and forth, all around. My car doesn't have issues when accelerating or anything, it's only start-up idle that it runs rough. After I drive it around for a bit, the idle runs a steady 15° advanced, and it runs great there.

The history behind my car:
I got it first with an engine with a snapped piston, so I switched it out and put in a brand new 3.8 V6 (same as the previous engine) my car ran great for awhile, then it started to missfire sometimes when I started it up after it had been driven, I've replaced just about anything you could think of, ignition control module, both camshaft and crankshaft sensors, 02 sensors, EGR, mass airflow sensor, throttle positioning sensor, and more. Then, I replaced my fuel injectors, and I believe, my engine started detonating. (Sounded almost like a knock of a piston, but it was higher pitch and different) boy that made my heart sink. We did a lot to try and figure out why or what that noise was, then my brother just messed with wires, and I think it was the idle air control he disconnected, and it stopped detonating, but the startup idle just isn't great until I put it in drive. I got an OBD2, and my brother suggested timing was the issue, and yes it seems.. but why? I've tried to use my old ignition control module, and my old camshaft and crankshaft sensors (they weren't bad, just got new ones for the new motor) I'm at the point I'm considering getting a new PCM, or at least seeing about sending it to someone who can possibly tune this issue out? I don't think anything is wrong with my car except that startup idle. I don't think the idle air control could mess up the timing? ~ Thank you.
 
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wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
I have been trying to figure out how best to help you. Clearly we disagree on HOW to go about fixing cars. It seems to me that the prefer the "part changing" trouble shooting method.

Just wondering.
  • What model year car are we dealing with? Are we to assume 1996-1998?
  • Have you reviewed the ODB2 mode6 misfire data? You are aware that the PCM will pull timing when misfires are occurring?
  • Have you done a through review of the charging system? Have you ruled out a bad alternator diode?
  • What are the long term and short term fuel trims (LTFT STFT) doing? How do they change at idle and under load?
  • HOW did you synchronize the cam sensor after each swap? Did you use the correct special tool?
  • What have you done to rule out a cracked/damaged balancer?
  • Is this car basically stock? If so, think about it. How is it possible that a stock car needs a tune to remove a detonating problem?
  • What have you done to rule out an exhaust leak?
  • What have you done to rule out a loose spark plug?
  • Have you considered running a compression test?
  • What have you done to rule out excessive carbon build up?
  • What have you done to rule out excessive PCV blow by?
IMO it's a really bad idea to attempt to try to "tune" a motor that is not healthy to begin with.

Do you have an ODB2 scanner that is capable of monitoring Ford Specific PID's?
 
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