Work coming along on the Condo
#351
Registered
#352
Registered
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
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
#354
Geronimo36
Gold Member
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.
#355
Registered
Join Date: Feb 2005
Location: oceanport nj
Posts: 1,626
Likes: 0
Received 0 Likes
on
0 Posts
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 .
#356
Geronimo36
Gold Member
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.
#357
Registered
Thread Starter
Join Date: Jul 2005
Location: Colts Neck,NJ
Posts: 2,149
Likes: 0
Received 0 Likes
on
0 Posts
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. But its all fixed now.
#358
Banned
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.
#359
Banned
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!
#360
Geronimo36
Gold Member
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!