Idle Air Control

Idle Air Control Motor

http://www.fuelairspark.com/Products.../Chapter11.htm

The purpose of the IAC motor is essentially to provide a controllable vacuum leak. The ECU can command the IAC motor to open and allow more air to enter the engine, or it can command it to close and allow less air in. More air will mean more engine speed and vice versa, so an IAC motor can be used to control engine speed. As seen in the graph below titled "Idle Speed vs. Coolant Temperature", a desired engine idle speed can be programmed by the user, and the ECU will use the IAC motor to keep the engine idling at this speed. However, as the throttle opens further and engine speed goes well above the targeted idle speed, the ECU will tell the IAC motor to close all the way in an attempt to bring engine speed back to its targeted value

Engines look great! Can't wait to see some #'s; both Dyno, and on the water!

Someone has it cause you already told me what power it made. ;)

IAC motor or sensor? Hopefully it's just the sensor cause you said that last year it would idle fine once the motor was in closed loop. It can also be a coolant temp sensor, that will cause the IAC to run funky until it comes up to temp.

I messed with a iac on jeep , every thread on a jeep site said that was the culprit of the symptom. Was like a solonoid basically , just got sticky. Don't know what its like on a merc but seems like a simple thing .

The merc efi's were notorious for having map sensor problems and even o'rings go bad in the intake plenum.

It's all tied together from what I had learned on the job and in EFI school (12 yrs ago now, lol). Even if you have a bad TPS with a "dead spot" it will give a faulty reading to the ECU and IAC will openup or stay closed when in fact the throttle is closed or open. Most of the time I found that it was the temp sensor throwing the whole system off but I guess we'll have to wait and see what the problem is/was.

I f'ing hate EFI..... Yeah it's great and all but such a ***** whenever you have an issue. My buddy Brian is just the opposite, he's a mechanic for Corporate Auto and he hates carbs, won't even touch em.

It was the IAC all the sensors were replaced. Between that and the fuel regulator it would load up and then when you would advance the throttle it would choke and stall. Then it was a biotch to restart. Sucks that it was the motor with the power steering on it. If it pissed me off I didn't have a choice i had to get it started to dock.:angry-smiley-055: But its all fixed now.:D

Nick's starboard engine had both a bad fuel reg. and IAC control. Engine runs great and was within 1.5-2 FT. LBS. of Torque and 1 HP of center. 3rd engine going on today. Both engines have 3 hours of run time on them. WE RUN ARE STUFF! And 18 pulls between the two.

The toolbox doesn't go thru the water Frank.....the boat does! And that little box has more Snap On crap in it than you can imagine!:offtopic:

I know Bro, it's fun to bust chops though! :) See, what's in my garage, as you can see I haven't cleaned up in a while, I'm too busy USING my boat!!.. :D

Personally, I probably have about half... I buy the good stuff for the crap that I know I need good stuff for and buy the average stuff on the things that I know I don't need to spend the extra cash on. I'd see all the guys I worked with spend $10K on the "Intimidator" tool box and I'd just shake my head. Some of the SnapOff crap is over rated! :party-smiley-048: