P0320 - Bucking when warm - HELP!
 

I see someone back in 2009 was having the EXACT same issue I am having now in 2015. I have contacted him to see if he still monitors this site, but in the meantime is there anyone else who can answer this? I just bought a 97 GT with over 129K miles. PCM/ECU just replaced as well as the crank sensor (about a month ago, I have his receipts). Runs perfect for about 15-20mins then starts violently bucking and jerking and gets progressively worse. This is what the other guy posted in 2009:

My 96 GT has been running like crap lately. I pulled this code when the cel came on. P0320. I replaced the crankshaft position sensor since that is what I thought was wrong. It did not help. The car runs good cold but after it warms up its like every cylinder quits firing. The tach goes to almost 0 but no lights on the dash like the engine is off. It will then start to run fine for about a second or 2 and does the same thing again. It bucks the heck out of you as it does this over and over. Now it started stalling out while taking off from a stop. I need help. I don't have any idea what else to try. The plugs and wires are good. And the harness from the CPS seems to be fine. Anyone have any ideas for me to try? I would greatly appreciate any advice. Thanks

Bump.

No one else has experienced this and "solved" the issue? I have seen similar posts but never anyone returning to post their findings. I am "hoping" that it is a loose or frayed wire but there are MANY things to check apparently with this situation.

*Update. It "bucked" a few times last night after only running for 60 seconds. But definitely gets worse the longer it is running.

What kind of bucking? Under acceleration and load? High RPM? Low RPM? is it consistent? Happen when you hold the gas pedal at a certain level?

What kind of bucking? The kind that throws you back and forth in your seat. The king when it dies then "kicks" in again the tires chirp. Violent. Seems like it happens at lower RPM (1500-3000rpm) but I don't usually run it up very high right now anyway. It is random. Until it has been running a while then it happens more frequently like once every 30 seconds. It doesn't seem like it happens so much a full throttle, more like just off idle to quarter. But again, I don't usually mash it to the floor.
Previous owner already replaced:
ECU "Main Computer"
Crank Sensor
One Coil
Spark plugs and wires (over a year ago)
Last night I disconnected the crank wire lead and pulled it out of the conduit 2' back. The shielded wiring was all intact no cuts or melting. It was rubbing against a pulley I believe for the AC compressor but it didn't brake the shielding or insulator. I taped it all back up, cleaned the connector and plugged it back in. I ran it last night for at least 30min pretty hard (very warm engine) and it did not "Buck" once! I am NOT getting my hopes up just yet but I was rather surprised it didn't happen not once. I will drive it again tonight for another 30min to see if it happens again.

P.S. I don't think I solved the problem, I think it just took a break for one evening. Please list anything you could think of that would be causing this issue.

On that Camshaft sensor when you replaced it, did you have it re-calibrated? if not then that may very well be your problem. Did the problems start before or after the camshaft sensor install?

Are you throwing any codes on the CEL? If not have you had it scanned? Still could be stored and not triggered.

I would replace the plugs/wires while you are at it will need it anyways.

Also wouldnt hurt to pull and clean your MAF

Let me know

Previous owner replaced the CRANK sensor NOT the CAM. As titled on this thread, I do have a code and it is P0320.
Ignition/Distributor Engine Speed Input Circuit Malfunction



Possible causes
- Faulty Ignition/Distributor engine speed sensor
- Faulty Crankshaft Position sensor
- Ignition/Distributor engine speed sensor harness is open or shorted
- Ignition/Distributor engine speed sensor circuit poor electrical connection
- Low battery charge
- Faulty Engine Control Module (ECM)

Cam phaser failure?
 

Would a cam phaser failure cause this bucking? What would phase lockers do to performance. I know the reason for the VVT is emmissions so to lock the cams down with phase locking blocks seems like this might help. But usually done when noisy on an idle.

not sure what u are asking the op has a 97 gt they dont have cam phasers or vvt

Very interested in the resolution to this problem, I have an engine acting the same way, not a Mustang though, and have been unable to solve it.