Ok, 496 Merc Mechanics : Fuel pressure?

[James'SS-24]

Check your tps sensor. Both the pulse counts and the output voltage. Mine has done that almost exact thing and that is all it turned out to be. You have to have a scan tool to do the counts but you can do the output voltage with a voltmeter. Should be between .65 and .70 volts @ idle. Mine was also starting really hard and when it did start it was flooded. But any where off of idle it ran fine! Also if this sensor is out of adjustment it won't register a code. :boxed:

[Beer-30]

Check your tps sensor. Both the pulse counts and the output voltage. Mine has done that almost exact thing and that is all it turned out to be. You have to have a scan tool to do the counts but you can do the output voltage with a voltmeter. Should be between .65 and .70 volts @ idle. Mine was also starting really hard and when it did start it was flooded. But any where off of idle it ran fine! Also if this sensor is out of adjustment it won't register a code. :boxed:
The last time I scanned it, it was .57V, which looked normal. Not sure exactly what the range is for idle.

[James'SS-24]

Hey Beer 30! So what was the problem? Always curious about this kind of stuff in case it happens to me! :rollside:

[bigkatboat]

Did you replace the IAC motor yet? Don't forget to use a new base gasket!

[Beer-30]

Did you replace the IAC motor yet? Don't forget to use a new base gasket!
Nope, haven't touched it yet. The plugs smoothed things out a little, but didn't cure it. I figure I will take it in after the first of the year and let them know what I had done so far and that I suspect the IAC. I figure that will be better than just starting to blindly replace parts. I'll keep all posted.

[Beer-30]

Ok, ordered a new IAC motor, since I found the same part number at Marine Power for $62 instead of $90 from Mercruiser. And, yes, I ordered a gasket too. Should be here Thursday. I figure a $62 dollar shot is cheap enough to gamble on saving $2-300 for dealer troubleshooting. Once I get it, I will update.

[purrfecttremor]

This is very interesting but I gotta ask whats a IAC motor? Sounds like one of thoes shity problems that only happen to Me.
Good luck Beer 30.

[Beer-30]

Idle Air Control motor. The computer tells it how much air to let in for proper idle speed.

[Beer-30]

That was it!
I just came in from changing out the IAC motor. Fired it up with the stick all the way back and it just started idling like it was supposed to. It had been consistantly doing the surging thing right off the bat - every start.
I had always tried letting it warm up and trying it again, still surged.
I let it come to full temp and then dropped the stick back to the stop. Nice idle. No surge.
$62 for the IAC motor.
$.79 for the gasket.
I had been waiting for a day when I knew I would have plenty of time to complete it. I had a free evening tonight, so I decided to try it - even if it turned out to be a lengthy process. Two TORX screws, and it came right off. Gasket came off clean. Popped the new one on and cinched it down evenly. Noticed that the clean air feed tube had come off of the IAC base again (it had still surged with or without it - so that wasn't it), so I cinched it to the base with a pair of zip ties.
On a scale of required Coors Lights; one being the easiest - ten being the hardest::
It only took 2.

[purrfecttremor]

Good info for all to remember.Cogratulations now if it was only summer!