Hey all, long time lurker first time poster. Ive got a new to me 93, 245 w/ LH 2.4, its an awesome machine except it idles extremely rough, the best way to describe is a surging idle; it also seems like it wants to shut down when I brake. Ive done quite a bit of research which has told me first to look at the IAC, I took out the IAC and cleaned it with no real change. However I found when I disconnected the IAC harness, the surging idle ceases to a nice smooth idle; albeit the idle is a little high. My question is, with my IAC unplugged how should my engine react? Is what I experienced normal or is this an indication that my IAC is broken?
I have also checked the OBD which gives me the 232 code. Im to understand that this boils down to a vacuum leak or something like that? Can anyone confirm this?

So Interesting developmentI cleaned the tubes going to the IAC the flex tube that goes to the TB and what I assume is the tube going to the PCV system? Any way, that last bit was disgusting, completely clogged. I cleaned it out along with other assorted vacuum lines etc. The good news the surging idle is gone! However, this was short lived when the CEL came on shortly after, 113 reading on the OBD.. I im confused however because 113 has 2 designations. One for fuel injectors and one for o2 sensor (I hear is a pain) so which is it? How do i tell

"I found when I disconnected the IAC harness, the surging idle ceases to a nice smooth idle; albeit the idle is a little high."

My understanding is that the IAC valve is supposed to provide air to the engine when the throttle plate is closed. Ie. Air forward of the throttle plate is routed through the IAC valve to behind the throttle plate. Otherwise the engine will stall for lack of air with the throttle plate closed at idle.

So if your engine doesn't stall with the IAC disconnected, suspect that the throttle plate may be open at idle when it shouldn't be. That's assuming that the IAC valve is closed when disconnected.

Also, check for vacuum leaks eg. through the brake booster and cabin air control.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Thanks trev29, that does make sense considering the hose routing. Ive also heard that I should be hearing a distinguishable click when I open the throttle blade, even a hair, the purpose of which is to essentially tell the IAC to close and allow the TB to do its thing? Any validity to this. I dont hear a click when i open my throttle, so this could also be another clue if it applies to the 2.4s.

before you get into all that make sure that the big accordian snorkle between the AMM and the Throttle Body dosen't have any cracks in it, Esp on the bottom side along the high part of the ribs. Shine a light inside and look on the outside.

Small cracks will open and close with the vibration of the engine...a forward/aft shift when braking.

If you find any use electrical tape or duct tape, or some black rubber sealant and see if it makes any difference.

Start simple and cheap.

Just to clarify the throttle switch is held by those two Allen head screws.

Your switch will click on a on 2.4 ECU's but the 3.1 uses a variable resistance throttle switch. It does not click that I know of but there must be a way to "time it" to the throttle plate. I do not have experience with them.

Like I said earlier, I knew more would chime in so now you are in the neighborhood of where the problems can be. For sure, if the throttle plate is closed enough the only air the engine should be able to get, is through the IAC. That way it has I A Control!

Good hunting for it, as your surging term can also be considered a synonymous term.

(:o)..?...Anonymous can be anybody, for a nobody! Whoops, I am going weird now!
Phil

"Whoops, I am going weird now!"

Yeah, I noticed. Your post is shorter than normal. Get well soon.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

The click will happen upon the Idle Air Control closing.
The IAC can be adjusted by using the screws that attach
it to the auto. If you loosen the two screws (don't unscrew
them to much, you can easily lose one or both), you can
then move the IAC into different 'positions' to 'adjust'
it. I don't remember if it adjusts side to side or up and down.
You can adjust/position it so that the click occurs upon closing
as it should.

Just be careful with those two screws, if I remember correctly
they use a small hex to loosen and tighten. Just to be safe
I would put a shop rag underneath the IAC just in case you do
drop one of the screws because you pulled it out 'too' much.

Hunting lost screws is no fun and can be avoided most of the time
by using a shop rag beneath the work area.

Good luck on the fix,
Joseph in New Mexico

crap.i may have posted a portion of my comment, or erased it...first time poster tonight too.my 240 idled rough and had stalling when I had tiny cracks in the lines.i went and purchased new vacuum line and it ran like a top.the 240 I had was great but very sensitive to any vacuum line being compromised and this was a pretty simple fix

carol, which vacuum line did you replace?

The first clue that you mentioned is a good one for a vacuum leak.

The line from the engine to the brake booster can be a large source for air.
Their connections or the check valve in it can go bad. It's the white right angle fitting that holds the hose onto the booster itself.

At any given time that you try to remove that check valve there should be a sucking of air sound coming out from around the grommet that holds it into the booster housing. If it's losing air, the engine will run rough until is gets caught up to removing air from the booster.

If you remove the check valve it should only pass air through it in one direction away from the booster and towards the engine.

If that check out as not the problem and the vacuum is gone, then you have a bad diaphragm inside the booster can. It will have to be replaced.
The junkyard is still a good shopping arena as you can practice taking theirs out so yours will then be a snap to do!

If only the check valve is bad try to get one from the junkyard as well. You can test the valve by using your mouth on the spot! A warranty comes with the whole booster unit otherwise.

I get mine there, as both pieces, when priced separately, cost to much anywhere else you go too. There are just too many to recycle and my time is on some sort of "giveaway plan" by comparison!

Get this checked out first since it happens when you brake, otherwise, there are several other causes for having idle issues that will introduce excess air but not so "brake" related.

Others can chime in, as I rattle along too much to go there, in one post! (:)

Phil

Thanks Phil, I will definitely be inspecting my brake booster vacuum line as well as others. Ill prob inspect my check valve while im there.

OBD codes..

http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

Good luck,
Joseph in New Mexico