Reckless32

Got a IAC Output fault today on the scantool. Actually got it once before, erased and it didn't pop back up. Took it off after my test run today, and it was "charred" around the bottom of the connector? Sooo, I'm gonna replace that and hopefully the soft alarm will go away like it did on the other motor.

Reckless32

Reflecting back it seems I did for a brief moment messing around under the hatch smell a faint odor of burnt plastic or something, and even made a quick look around both motors, and found nothing (burnt portion of plug is out of view unless off the motor). The scan tool of course started consistently giving me the "IAC Output" fault; "PCM Error" if I attempted the IAC test; and only "90% power" available.

I don't honestly think the fresh water flush kit I installed had anything to do with the 2 per minute beeps, and that it was purely coincidental. If it had, then I would suspect the "Sea Pump PSI Lo/Hi" fault would've popped up now that I know there is one and have my own scantool. Of course I won't know for sure until I replace the IAC valve this week and re-test. I will get an additional one just in case the other motor's IAC is not far behind (since in the beginning I was getting a double set of 2 per minute beeps).

Now that Dave N provided me the Fault code list, a lot of things makes sense now in terms of the alarms etc. This has been a PITA but also a great learning curve for diagnosing future symptoms/issues myself.

Dave_N

Seems pretty clear that the IAC is bad on one engine. On the other engine that is no longer giving an alarm, what faults were stored in the freezframe memory?

Reckless32

The usuals plus overspeed, guardian, and yes the IAC. But I had gone thru a remove, clean, replace cycle in the beginning in addition to re-positioning the T-fittings, and the IAC code never appeared again in the active fault listing engine off switch on, and while at idel. I'm buying a second one just in case the other decides to take a dump as well. I also removed that harness connector going to the transom with no results either prior to the IAC discovery.

I ran the individual IAC test where it asks you to increase/decrease Idle RPM at normal operating temp on each engine. The port said PCM couldn't Error. The starboard showed the % increase but the engine did not increase in actual RPM (that I noticed) thru 50%. I pulled and looked around the starboard (now good side) IAC and saw no signs of burnt or charred plastic like found on the port IAC.

Reckless32

While on the subject of running individual tests, to do an injector test it says to unplug/disable the fuel pump. Does that mean only the boost, or both pumps port & starboard?

I have found and cleaned a lot of crud in both injector sets this year, and I'd like to run the injector test but I'm not sure of the fuel pump warning.

Also any gouge on running the Auto-test?

Edward R. Cozzi

Didn't somebody back in post #9 mention something about the IAC? You guys have no respect for us old white hair MFers!

BillR

In Reckless' case; it has nothing to do with lack of respect - more like the hardness of his head. LOL

Dave_N

In the help section of my Diacom software this is what it says about the injector test;
"The Fuel Injector output test allows individual fuel injectors to be actuated in order to verify their operation. The fuel injector under test will be fired at a rate equivalent to 1600 RPM. This test will help the technicians verify that a particular fuel injector is receiving a command signal from the PCM. This test will not reveal if an injector is clogged, internally leaking or mechanically worn."

As far as the IAC test, I have never been able to get it to work on any engine. The symptoms of a failed IAC are usually pretty appearant and will set a fault most of the time, so it's not really critical, but it would be nice if the test actually worked.

It's really strange how both engines had an IAC fault right after the flush kit installation, and niether engine showed any symptoms. Just proves the importance of a having a scan tool.

Dave

Reckless32

It's called good old fashioned perseverence Bill...

Ed it wasn't ignored, just couldn't be proven at the time until after i got the scantool in hand and THEN was able to isolate it. Otherwise I would've been pulling and yanking for nothing.

Dave it's good to have verified the IAC test doesn't work. The bad motor definitely shows "PCM can't initiate the test **Error** or something to that effect and 90% power. There was never any "Water pressure" faults at all like one would assume if it was the pump sensor being fooled. I picked up my two new IAC's today and will install shortly and verify the fix, or a continued Grimlin.

Yeah my book says the same for the Injector test, as does the scantool warning when entering the test. What the book doesn't say specifically for 496's is do we disconnect both pumps (boost & primary), or is just the boost sufficient? I'm afraid to try until I find out for sure though i don't think there's any indication of problems with the injectors since I cleaned both motor sets..

Dave_N

To minimize flooding when doing the test, I would disconnect both pumps and even bleed off the pressure at the schrader valve before doing the test.