Intermittent Stall, P0320

Been a while since I've posted here. The expy has been cranking longer/rougher, idling rough when the engine's cold (one time it shut off), it stumbles around 2000 rpm driving in the city occasionally, and it almost dies when shifting out of overdrive on the highway.

Replaced spark plugs with motorcraft <200 miles ago, coils are excel yellow with 50k miles on them.

When the engine is warm, the issues only happen around 2000 rpm. Almost every time it stalls the green cruise control light comes on, but only while it's stalling. Get off the gas and it runs fine, cruise light goes back off.

I had to do this repair in order to bypass the non replaceable fuel pump relay in the fusebox about a year and a half ago, maybe it's relevant.


Code is P0320

Description:

Symptoms of a P0320 engine code may include: Malfunction Indicator Light On Engine cranks but will not start Misfire, Hesitation, Stumble, Lack of Power

What I've done:

• replace camshaft position sensor (no improvement)
• replace crankshaft position sensor (no improvement)
• visually inspect wires to sensors
• found loose ground on battery negative
• found loose connection to hot lead on alternator (noticeable improvement)
• tested resistance between alternator hot and battery positive

Any thoughts appreciated

Did you inspect the harness that passes over the top of the AC line there by the battery ? It's a known issue for wire chaffing and shorting to the AC line. If you find it chaffed or exposed wrap some electrical tape around it and secure the harness up off the AC line with a zip tie and you should be good to go.

I saw that video and inspected that wire visually. It doesn't have any sign of wear. Do you know what that wire leads to? I want to check for resistance. Thanks for the quick reply.

Try running a OBDII car scanner with the car ON, scan for codes to see if it detects a misfire from one of the engine cylinders. I had poor performance at certain speeds, to include long cranking at startup, and never had the engine light come on. The scanner detected a misfire in cylinder 4 and I changed the ignition coil connector and the ignition coil, which fixed the issue. A few months prior, I had changed all the ignition coils so I didn't think this could be the problem.

03 XLT 5.4L 195k

Can I do that with a basic scan tool or does it need to provide live data?

Yes, I believe so... I have an old AutoXray scan tool that I use for my truck. But, its not the live data you want to setup the scanner for, start the car and with the engine running, scan for fault codes.