When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey everyone, new here and hoping to get some guidance from the experts.
Truck: 1996 F350 7.5L (460) with E4OD. 2wd Centurion
Background: Ran great all summer long put around 15,000 miles and it was great. parked it this winter ran it for a quick second with the postive and negative wires loose and the truck went nuts shut it off and tightened the connections and now i have this issue.
Issue:
Truck runs and drives great when cold. Once it reaches operating temp, it starts misfiring and the tachometer goes crazy. no power under load. If I give it more throttle, it holds around 1800 RPM and smooths out somewhat, but the tach still jumps around. When I unplug the 2-wire ECT sensor, it runs great even when warm (check engine light comes on, obviously).
Here’s what I’ve replaced so far:
Distributor
TFI module
Ignition coil
Spark plugs (look recently replaced and in good shape)
Plug wires
Engine Coolant Temp (ECT) sensor
O2 sensors
Battery and alternator are new
Verified coil positive voltage ~11.7V key on engine off
Additional info:
Sharp random pops when warm
Tach becomes erratic only once hot
Transmission codes present:
626 Coast Clutch Solenoid circuit fault
624 EPC solenoid circuit fault (KOEO and continuous)
637 Transmission oil temp circuit above max voltage
It runs perfect cold every time. Problem only starts once fully warm. Unplugging ECT makes it run great.
At this point I’m leaning toward a wiring / ground / voltage issue rather than fuel or ignition components since so much has already been replaced.
Any insight on shared grounds, PCM power feeds, or common 460/E4OD harness issues would be appreciated. Trying not to throw more parts at it.
Check your fuel pressure. https://www.ford-trucks.com/forums/1...rd-trucks.html
I agreed with above. Once it goes into closed-loop, it starts metering back fuel. If your fuel pressure is low, it'll screw the ratio up.
Those codes may be caused by a damaged transmission wiring harness on the passenger side of the transmission.
Nice truck, btw.
Last edited by Prototypemech; Mar 3, 2026 at 10:52 PM.
After checking the fuel pressure
Check the codes, check the ignition module, check the capacitors in the processor
I would have a spark tester on there and a fuel pressure gauge taped to the windshield and go for a few test drives
I’m going to check the items you mentioned and review the thread you shared. I’ll also measure the fuel pressure (PSI) and report back with what I find.
I really appreciate all the help! I got the truck on a smoking deal and definitely don’t want to get rid of it.
I’m going to check the items you mentioned and review the thread you shared. I’ll also measure the fuel pressure (PSI) and report back with what I find.
Make sure to do what manicmechanic007 says and watch the gauge while driving to see what it does under load.
Today I went out to the truck to run the fuel pressure test that was recommended. When I went to start it, the tachometer immediately started going crazy, jumping all over the place. While I was watching under the hood, I noticed the distributor rotor was spinning extremely fast, much faster than what I would normally expect.
The truck ran briefly and then died shortly after.
This happened before I could even get a fuel pressure reading. The behavior seemed pretty abnormal, especially the tach bouncing around and how fast the rotor appeared to be spinning.
I took a couple videos of what it’s doing and attached them below.
Has anyone seen this happen before or have any ideas what could cause this?
Maybe a shorted out ground possibly thanks
Here are the links to the videos of whats going on
That is a brand new distributor so maybe a bad ground going to the PIP? What is odd is if I turn it off let it sit for 20-30 second it runs and does not do that until it goes up in temperature and it starts acting up again
That is a brand new distributor so maybe a bad ground going to the PIP? What is odd is if I turn it off let it sit for 20-30 second it runs and does not do that until it goes up in temperature and it starts acting up again
New does not mean good, do you still have the old distributor? Put it back in and see if the problem persists.
I went ahead and reinstalled the old distributor, but it’s acting the exact same way as before. I’m starting to think I might have a grounding issue with the ICM. When I was mounting it back up, the module was extremely hot and actually burned my finger. This is a brand new OEM Motorcraft ICM, so I wouldn’t expect it to be overheating like that.
Has anyone seen this happen before or know if a bad ground could cause the ICM to get that hot making the ignition module go nuts
There is a reason why the ICM is mounted on a heat sink. There should also be a layer of thermal paste between the ICM and heat sink. They do get hot enough to scorch your finger when there is nothing there to dissipate the heat.
I replaced ICM in my 95 F150 and apparently didn't use enough (or the right kind) of grease between the ICM and the heat sink. Lasted about 6 months. Latest replacement I shlacked that dyalectic grease all over that bad boy. But I never had the problems you have. I would get crank, no spark, consistently.
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
