98 GT - possibly bad PCM causing misfire

[Chiper91]

I am having subtle misfire in 2nd and 3rd between 1.5k and 2.5k RPM under constant throttle.

Replaced and cleaned all the possible culprits Narrowed it down to electrical issues. First of all, when KOEO my CEL does not appear on the dashboard along with the other lights. The bulb was replaced, did not help. Misfire started after my battery suddenly died after car was parked for 2 hours with no lights on
Misfire seems to disappear for the first 10-20 min after the negative cable got reconnected to the battery.

At this moment I am confused about the whole PCM, ECU and CCRM deal? is PCM and ECU the same thing and CCRM is a separate module? How do I test them for proper functionality?

Any advice would be appreciated

 

[AutodesignJohn]

CCRM controls the fans and similar body accessories. It is in the passenger wheel well and is just a bunch of relays soldered to a board instead of being replaceable. ECU and PCM are the same thing. To test an issue like that requires you to pull the big plug behind the passenger strut tower where the fuel lines come from. If you need the test procedures/ service manual, send me an email and I can provide them.

 

[wmburns]

is PCM and ECU the same thing and CCRM is a separate module? How do I test them for proper functionality?

PCM and ECU are names for the same thing.

As far as how to test the CCRM. Does your car start and run? If yes, then the CCRM is working.

I am having subtle misfire in 2nd and 3rd between 1.5k and 2.5k RPM under constant throttle.

Replaced and cleaned all the possible culprits Narrowed it down to electrical issues. First of all, when KOEO my CEL does not appear on the dashboard along with the other lights. The bulb was replaced, did not help. Misfire started after my battery suddenly died after car was parked for 2 hours with no lights on
Misfire seems to disappear for the first 10-20 min after the negative cable got reconnected to the battery.

Advice. Don't replace a PCM as a trouble shooting method. Only change a PCM after every other possible cause has been ruled out. Frequently swapping a PCM simply exchanges one problem for another. Besides thing how much it would stink to replace a PCM only to have the same problem?

For example. What have your done to rule out a charging system problem?

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

If you really want to perform a through test of the PCM then learn how to use an ODB2 scanner.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

For example if a misfire is suspected, then there is something causing it. Could it be an unstable CKP sensor? Maybe. Graph it and perhaps it will show itself.