2001 4.6 misfire on one cylinder

[terry274]

Originally Posted By: Trav
Just for the heck of it change the plug again. It would be very rare and I have only had one or two in my whole career that were truly DOA but its worth eliminating if nothing else.


When I did the compression test on that cylinder I installed another new Motorcraft sparkplug. Thanks for the suggestion though.

 

[StevieC]

I wonder if it's a valve not opening.

 

[Ethan1]

Originally Posted By: mk378
Most of those codes look old from a previous one-time event like running the battery down. Erase them and see which come back.


YES. I've seen cars with dozens of errant codes from a low battery.

 

[Ethan1]

Did you come across Relative Compression Test in Forscan?

 

[terry274]

Originally Posted By: Ethan1
Did you come across Relative Compression Test in Forscan?


Not yet, I want to get the battery fully charged, then clear the many codes to see what I actually have.

 

[terry274]

I hooked my OBD adapter to my truck (1996 F150) to try a Relative Compression test in Forscan. I don't really see a way to do that. What I find on the internet is people hooking an amp meter to the battery cable to measure current while cranking.
This is all tied in to their SnapOn diagnostic machine.

Forscan does have an oscilloscope function but I don't entirely understand what I'm seeing.

 

[terry274]

Other than poor fuel economy, a rough running engine and loss of power what would the problem with running the truck with the coil disconnected and the fuel injector disconnected?
Is any long term damage likely to result from the dead cylinder?

 

[Trav]

Originally Posted By: StevieC
I wonder if it's a valve not opening.


Its possible a cam follower fell off, a worn lobe would be noisy but a dropped or partially off follower wouldn't. I doubt it would have 120 psi cold closed throttle compression if that happened but who knows. Worth a look see for sure.

 

[terry274]

I didn't think to post pictures of the spark plug earlier, so here they are now.

 

[bdcardinal]

Originally Posted By: terry274
Other than poor fuel economy, a rough running engine and loss of power what would the problem with running the truck with the coil disconnected and the fuel injector disconnected?
Is any long term damage likely to result from the dead cylinder?


Burned up catalytic converter.

 

[Colt45ws]

Originally Posted By: bdcardinal
Originally Posted By: terry274
Other than poor fuel economy, a rough running engine and loss of power what would the problem with running the truck with the coil disconnected and the fuel injector disconnected?
Is any long term damage likely to result from the dead cylinder?


Burned up catalytic converter.

Unplugged fuel injector.

 

[bdcardinal]

Originally Posted By: Colt45ws
Originally Posted By: bdcardinal
Originally Posted By: terry274
Other than poor fuel economy, a rough running engine and loss of power what would the problem with running the truck with the coil disconnected and the fuel injector disconnected?
Is any long term damage likely to result from the dead cylinder?


Burned up catalytic converter.

Unplugged fuel injector.


Missed that part, disregard.

 

[terry274]

This truck has bad door ajar switches and the interior lights stay on a long time, leading to a partially discharged battery. I disconnected the battery overnight and charged it with my battery minder. It was fully charged this morning. I cleared all the codes and drove it to get it warm.
I can't feel the misfire any longer and it's not setting a code.
I checked for misfires with Forscan (awesome program) and it generated over 500 misfires in about ten minutes but never set a code for misfire.
It does set the following code repeatedly:

===GEM DTC B1302===
Code: B1302 - Accessory delay relay circuit failure

Module: Generic Electronic Module

Diagnostic Trouble Code details

Accessory delay relay circuit failure

===END GEM DTC B1302===

===GEM DTC B1398===
Code: B1398 - Left Front Power Window Relay circuit failure

Module: Generic Electronic Module

Diagnostic Trouble Code details

Left Front Power Window Relay circuit failure

===END GEM DTC B1398===

===GEM DTC B1365===
Code: B1365 - Ignition start circuit battery short

Module: Generic Electronic Module

Diagnostic Trouble Code details

Ignition start circuit battery short

===END GEM DTC B1365===


The B1365 has me concerned.

I pulled the fuse to the interior lamps for the time being.

 

[Trav]

At least you know where to start looking. IIRC these sometimes had battery cable issues at the starter motor terminal, I have seen more than a couple of cables almost rotted right off. Start there.

 

[terry274]

He has the truck now. I have to work all week and won't be able to work on his truck. It was weird, I left my house and drove to their house and it ran fine all the way. This was a 25 minute drive.

I picked up my daughter (my son in law works long hours on the weekend) and headed back to my house. About half way home we stopped for gas. The miss returned. It ran well above 1300 rpm but misfired at idle.

The service engine light came on as soon as the miss occurred. PO307. Is it possible that the problem is in another cylinder and the PCM is indicating the wrong cylinder? That still doesn't explain why it was ok at the start of the trip today.