Idle Air Controller Stuck Open/Temp Gauge Issue

[ultratiger89]

Hi All,

Last year my IAC failed and I replaced it with a new one. Prior to it failing the motor became hard to start and I had to give it some throttle to start it. I thought the IAC was to blame but after replacing it the motor is still hard to start. I had the boat in for lower unit lube change and asked the mechanic to check my temperature gauge as it reads around 200° when running. Anyway, he said the IAC is stuck wide open and he doesn't know why. I was wondering if any of you have had this experience and know what might be causing it. Also, can the temp gauge be calibrated? It's running 40° higher than the actual temperature. I borrowed his laser temp gun and verified the T-stat housing was running at 160°.

Thanks,
Quin

 

[fc3]

year, engine, and model? Karnak doesn't work here.

 

[beachcombersc]

year, engine, and model? Karnak doesn't work here.

1:18-1:30
"Sixty minutes.... How long the gas shortage will last once the price goes to a dollar..." Johny Carson

 

[ultratiger89]

year, engine, and model? Karnak doesn't work here.

2003 350 Mag. I assumed all IAC's worked the same. Thanks.

 

[fc3]

No, there are different types. You don't know the problem with the old IAC so we can't determine if you have the same problem or a different one with the new IAC. Using the service tester, it is quite simple to exercise the IAC. The tester sweeps it from fully open to fully closed. With a known good part installed, a tech can determine with the tester if the IAC is bad, the EFI unit is bad or there is a wiring problem. Mostly likely, it's the IAC. For some reason, the newer design isn't as robust as the older ones. Probably because there's more plastic in the new units.

You can't calibrate the temperature gauge. Check the resistance of the sender vs. what the book says should be the resistance and replace if it's not at spec.

Best regards,
Frank

 

[ultratiger89]

Frank, thanks, for the reply. I know the old one was bad because it set off the alarm, whatever type of failure causes that, which I would think the stepper motor burning out. I put the new one in but still had the starting issues, just no alarm anymore. I figured it was something else and just lived with having to provide throttle to start it. There's something going on telling the IAC to open up 100%. I have my mechanic looking at it this week. He didn't have time last week to look at it but just told me it was showing wide open on the computer.

As for the sender, I replaced that last year also, and it read lower last year than it does now, even though the boat is running at the proper temp of 160°. Even though it doesn't move much it's a psychological thing that makes me want the gauge to read the correct temp!

 

[ultratiger89]

Well, problem found, the IAC muffler was clogged. He also said the flame arrester was clogged upquite a bit too, I looked at the other day and didn't see anything. He said there was dog hair in on it. We have two Pomerainians we take on the boat, never thought dog hair would get in there! Anyway, just wanted to let ya'll know incase this happens to your boat. Guess I need to do a monthly clean of the flame arrester.