Welcome Guest [Log In] [Register]
Posted ImageWelcome to the all new Geo Metro Forum. We hope you enjoy your visit.

You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are features you can't use and images you can't see. Registration is simple, fast, and completely free. If you're already a member please log in to your account to access all of our features:

Join our community!




Username:   Password:
Add Reply
IAC problems
Topic Started: Apr 12 2010, 12:01 AM (3,219 Views)
92GoCart
New Member
[ *  * ]
I recently fixed a '92 Geo Metro 1.0 that had a broken piston skirt and had been sitting for many years. One problem I have is with the idle air control. Once warmed up and idling normally its all fine until I open the throttle just a little and then let it shut again it won't idle down right away. The IAC will sit there clicking away as it keeps the idle up but will soon start slowly coming back down to normal (probably less than 30 seconds to get back to normal idle). I opened up the IAC and found the little solenoid plunger/rubber stopper part had one broken leg out of three that suspend the center part of the valve. I figured this might be the problem so put a new one on but it does the same thing. It runs fine if I just unplug it or plug the vacuum line. It still has a cold high idle without this and an A/C high idle valve so I'm not really clear when this IAC valve is used. I can't seem to hear it kick in when I put a load on the engine with the lights and blower. Any ideas where to start? I'm not clear what is supposed to trigger this valve so don't know where to start. I cleaned all the grounds I cold find. The valve should be fine since its new. I thing the problem lies in whatever is controlling it. It can't be a vacuum leak or it would be in high idle mode all the time and its only affect when this valve is plugged in and receiving a signal.
Offline Profile Quote Post Goto Top
 
crankcase


I would suggest checking all vacumm hoses carefully. As I understand it, the IAC effects the idle via air/fuel ratio and performs the same function as a choke. It opens and closes with the demands placed on the engine at cold and warm idle conditions and is actuated by the computer.
Offline Profile Quote Post Goto Top
 
Bad Bent
Member Avatar
Facetious Educated Donkey

"It still has a cold high idle without this and an A/C high idle valve so I'm not really clear when this IAC valve is used. "

Good one crankcase. Probably correct. I just checked my intake manifold and the temperature sensor that we say is for A/C is on the passenger side of the exhaust manifold. Your's should be connected, 92GoCart. If it is and it has been on there for the life of the car then perhaps it has developed a layer of corrosion and is not reading the true temp of the manifold? :dunno Just a SWAG but the coolant hoses on the Throttle Body may be cold also. Just a thought.
Offline Profile Quote Post Goto Top
 
92GoCart
New Member
[ *  * ]
I don't see how it can be a vacuum leak as I have normal idle with the IAC unplugged. It only high idles for 20-30 seconds after cracking the throttle when warm and then slowly comes back to normal during those 20-30 seconds. If it was a vacuum leak it would high idle all the time regardless of the IAC being plugged in or not. I checked the TB coolant hoses for heat days ago and they get hot as they should. Maybe I will try to get a little video clip at some point. What's odd to me is that its only when the throttle is opened that it does this. I will have to do more snooping around when I have time. I also need to dig around in my shop manual and see if it says anything about this system. Thanks for the replies.
Offline Profile Quote Post Goto Top
 
crankcase


I confess I am speculating, but what I was thinking was that the computer is getting an erroneous signal from some system (vacuum leak) and trying to run the IAC based on that.

I need to familiarize myself with the idle speed control system more. I have a related idle problem that remains unfixed, so I am very interested in hearing your experience. I’m doing finals in school for the next few weeks, so there's not much spare time to turn wrenches, but I plan on putting a few hours in this weekend.

The closest factory service manual to the 1992 I have is for the 1993. There is no difference I know of between these cars - I have both - but I’m sure there must be. They look the same as near as I can tell.
Offline Profile Quote Post Goto Top
 
92GoCart
New Member
[ *  * ]
crankcase
Apr 13 2010, 11:13 PM
I confess I am speculating, but what I was thinking was that the computer is getting an erroneous signal from some system (vacuum leak) and trying to run the IAC based on that.
Oh okay I see where you were going with that now. Yeah I don't know. I just need to spend more time on it and see if I come up with anything. Just started driving it less than a week ago so haven't had a lot of time to work the bugs out yet. For now I'm driving it with the IAC unplugged and haven't even missed it so that's a good thing.
Offline Profile Quote Post Goto Top
 
crankcase


I did a little homework and then some car work on my daughter-in-law's 92 idle problem. I will list my experience as best I can: I discovered that high idle happens when the IAC is open and sucking air in, bypassing throttle plate and going directly into the throttle body. This should happen when no signal is applied and air is sucked from the air filter area. If you plug this line, the idle should lower. The IAC must have a signal on it, which is really 12V pulses at several per second (depending on engine needs) to stop the air flow. If the IAC is not plugged in, there is no way to close the air supply and lower idle. This does not correspond to your situation I understand, and I'm wondering if one of us has listed a detail wrong, probably me. Also, it could be the idle control may go into an open loop mode if IAC is unplugged (no sensor feedback and not active correction). I will double check tomorrow.

I had the same problem you did with the IAC plunger. I pried the IAC open (bent back the 4 fingers) and checked. There is a little plunger that has spring tension from a funky type of spring in there. The spring is a flat brass piece that has 3 little legs that break with normal wear. The plunger, actuated by a solenoid, gets pushed up, the valve closes, and the idle lowers. The broken spring/plunger on the 92 was replaced with one from a broken IAC.

The 92 also had a clog in a coolant line at the throttle body. It was the small lines in the back and passenger side (actually clog was in throttle body). The small hoses were not getting hot, such as the one that goes to the black metal coolant pipe leading into the water pump. I have read that coolant lines get clogged at the throttle body and cause high idle, but assumed it was the bigger one (UH - WRONG).

Hot coolant goes through a short hose on throttle body to another section of the throttle body a few inches above (all on passenger side). The coolant then flows past the coolant sensor and exits the throttle body toward the top (directly to the rear of the car). That hose then goes to the black metal pipe leading to the water pump.

After these 2 repairs, the car now idles at 840 RPM for the first time in the two years we've had it (used to be around 1500RPM).

Edited by crankcase, Apr 17 2010, 10:41 PM.
Offline Profile Quote Post Goto Top
 
smokstac
Member Avatar
Member
[ *  *  * ]
The 98 1.3L 16v engine has a small tube going from the intake to the IAC assembly. The head side of the passage is large while the intake manifold reduces the passage to a small hole. The intake I just pulled from the PnP had a nearly clogged passage on it.
Offline Profile Quote Post Goto Top
 
92GoCart
New Member
[ *  * ]
Well I messed around with the IAC some more today but it's still not fixed. I did all the tests on the TPS and it checked out. I found that the IAC has power all the time so the ECM must pulse the ground to activate it. I can't get it to activate when loading the engine (lights on, blower on hi). The only time it activates is when I open the throttle a crack. I did more checking for vacuum leaks and found nothing. All the hoses appear to be in good shape. As I said before I have normal idle until I crack the throttle at which time the IAC comes online then slowly tapers back down to a normal idle in 30 seconds or less. Makes me wonder if the ECM is the problem. So for now I continue to drive with it unplugged.

Edit: I just found a brand new factory service manual on eBay for $30+4 shipping covering my '92 so maybe this will help me out. As usual these aftermarket manuals are VERY lacking and try to cover too many years so leave out a lot of detail.
Edited by 92GoCart, Apr 18 2010, 11:50 PM.
Offline Profile Quote Post Goto Top
 
LittleSilverCar
Member Avatar
Elite Member
[ *  *  *  *  * ]
My IAC was stuck in the OUT position and all it did was CLICK-CLICK-CLICK-CLICK-CLICK- and rev the engine. I bought a new IAC on ebay for $50 and put it in, all is good. As long as the TPS is adjusted in the proper position, the IAC will work and not break again. Look up the part number online
Edited by LittleSilverCar, Apr 23 2010, 05:46 AM.
Offline Profile Quote Post Goto Top
 
92GoCart
New Member
[ *  * ]
I did replace the IAC and this didn't fix it (did need it though as it had a broken part inside). I checked the TPS but there was some confusion between the two after market manuals I have as well as the different years so I will probably check it again when I have my REAL factory SM in hand.
Offline Profile Quote Post Goto Top
 
crankcase


As I recall there are two similar TPS, one is a 3 wire and the other a 4 wire? The 94 at least is different than earlier models. They are not compatable, but both can fit either harness.
Offline Profile Quote Post Goto Top
 
92GoCart
New Member
[ *  * ]
Mine is the 4 wire. One part if it is simply an on/off switch for the idle circuit I think. I tested that and it was working fine.
Offline Profile Quote Post Goto Top
 
No1b4me
New Member
[ *  * ]
92GoCart
Apr 12 2010, 12:01 AM
I recently fixed a '92 Geo Metro 1.0 that had a broken piston skirt and had been sitting for many years. One problem I have is with the idle air control. Once warmed up and idling normally its all fine until I open the throttle just a little and then let it shut again it won't idle down right away. The IAC will sit there clicking away as it keeps the idle up but will soon start slowly coming back down to normal (probably less than 30 seconds to get back to normal idle). I opened up the IAC and found the little solenoid plunger/rubber stopper part had one broken leg out of three that suspend the center part of the valve. I figured this might be the problem so put a new one on but it does the same thing. It runs fine if I just unplug it or plug the vacuum line. It still has a cold high idle without this and an A/C high idle valve so I'm not really clear when this IAC valve is used. I can't seem to hear it kick in when I put a load on the engine with the lights and blower. Any ideas where to start? I'm not clear what is supposed to trigger this valve so don't know where to start. I cleaned all the grounds I cold find. The valve should be fine since its new. I thing the problem lies in whatever is controlling it. It can't be a vacuum leak or it would be in high idle mode all the time and its only affect when this valve is plugged in and receiving a signal.
Wow, All this help here and No sure answer?

Last time I give my opinion on a problem here I basically got slapped on this forum (THEY JUDGE YOU BY YOUR FIRST FEW POST) so be careful.. Lets see if this goes a bit better? If not I'm sure the same old pesters will jump right on in this thread an try N chop me down for something the feel I've dreamed up. (I can't help I Live Breath and eat geos.)

Sounds like to me your problem is in the Exhaust system, Either one of your 02's or malfunctioning or you have a Bad Catalytic converter! This is whats throwing your Iac off. There's also a module just under the glove box area, just to the right of the shifter in its saddle, It also controls the Iac, I doubt that module is your problem.

Just exactly,, how old is your Catalytic converter? There are 2 pins on the 02 you can oem out, I don't remember the 2 however its 2 of the 4, so some sorta reading should be recovered in about 2 min's of testing. Test both downstream and upstream.

02's can be bypassed, But it wouldn't be California street legal :lol

Offline Profile Quote Post Goto Top
 
Bad Bent
Member Avatar
Facetious Educated Donkey

There's more going on here, so the latest thread is Detonation, need help, back in June. The issue there is detonation and you can see the cam timing and restricted exhaust were mentioned. Ignition timing is 3o and there was flutter in the exhaust manifold vacuum at the MAP. Should be 8o and there could be a bad valve or as was suggested the exhaust is restricted, as you suggest. If combustion was incomplete due to the timing the O2 sensor would be sending a low signal and it might have fried the Catalytic converter, eh.
We have not seen 92GoCart in a few weeks so we don't know what is going on except the suggestion that he was going to decapitate the engine to sort it out.
Offline Profile Quote Post Goto Top
 
1 user reading this topic (1 Guest and 0 Anonymous)
Go to Next Page
« Previous Topic · Engine Tech & Diagnostics · Next Topic »
Add Reply