Sounds like you have been pretty thorough. I re-read the post and it looks like you have checked most everything.
Have you tested the Air Regulator? That item is used exclusively when the engine is first started to raise the idle until it comes up in temp by giving the engine a little more air, just like opening the throttle a slight amount. It doesn't matter how warm it is outside, that item needs to function when it's down to ambient temperature.
If you could borrow an ECU it would be good to verify your ECU isn't an issue. It's not unheard of for a component in the ECU to go bad.
Just to confirm, you set the AAC (IACV base idle screw) and then plug in the AAC with the engine running and nothing happens RPM wise?
You can verify if the AAC wiring is good from the ECU plug to the AAC. Pin #4 on the plug
Modified by Zwicked at 12:16 PM 7/21/2009
Please help me someone, low/stumbling idles - goin crazy here...
Re: (redincali)
glad it helped some, its not extremely hard to replace but its a learning experience for sure. i agree with zwicked on waiting for that, its hard to justify on this one problem so far. the diagnostics show harness replacement as being one of the last resorts. it gives fusible links and the ignition switch as possible points of fault as well b4 the harness. try the diagnostic for it and then the other items and as you eliminate things maybe something will stand out for sure. i would sure check the ecu to make sure it was sending a signal though, if it is then you know its likely something between the two items. b4 my mechanic was killed he did tell me these cars were different to work on i see what he was talking about just looking through these forums lol
RIP Snake
RIP Snake
Re: (emt2898)
thanks, both of you. i have checked the connection on the air regulator but haven't taken it off to check the part itself (i hate the tight engine bay). can the clip be taken off the ecu without harming it or will it reset something that i have to take my vehicle in to get it working? i only have one friend with a Z, his is a 90 auto n/a, mines a 91 5sp n/a. so i dont know bout swapping ecu with him and i dont know anyone else to try with.
ill try to check the #4 wire tomorrow. what should i be looking for, any signal at all? i have tried to be thorough, not half assed or guessing lol, and yes that is how i set the idle. unplugged, set idle, replugged, and no change. thanks again.
ill try to check the #4 wire tomorrow. what should i be looking for, any signal at all? i have tried to be thorough, not half assed or guessing lol, and yes that is how i set the idle. unplugged, set idle, replugged, and no change. thanks again.
Re: (redincali)
****BY THE WAY...the manual says for testing the AAC connection: voltage briefly decreases from battery voltage 11-14 volts when the engine speed is raced. EF&EC section, page 173
I would take a multimeter, set it to the 20 VDC range, and insert 1 probe in each of the 2 connector contacts and run the engine and see if you get a voltage reading before pulling the ECU out.
I would still recommend you first check the Air Reg and the connector cleanliness. It only has 2 bolts holding it on and no gasket. Once it's off, take and hold it up to the light. You should see a sliver of light coming through. Next, connect it to 12 volts and wait about 5 minutes. Now when you peer through it, the sliver of light should be gone. If that's the case, all is well. If not it's gummed up or burnt out. They can gum up in the closed position and not allow high idle when not at operating temp.
Did you run o2 diagnostics as you mentioned? I remember when mine were bad it idles poorly and smoked a lot, not that it stalled though. Still worth running the diag to be sure. It's nice to have everything confirmed working and in spec to make the search of faulty items easier.
I think the auto ECU can be used in a 5 speed but not the other way around.
Removing the ECU is the same as disconnecting the battery as far as wiping anything out and relearning goes. No biggie.
Disconnect the battery before removing the ECU connector. The ECU has 3 bolts holing it down, and then you can get at the connector which has a 10mm bolt holding it in. It needs to be unscrewed and then pull on the connector while doing that. I would run a piece of wire from the AAC plug to ground and use a multimeter or continuity tester just to prove out that the wiring to the AAC is ok.
When you reinstall the ECU connector, make sure it goes in nice and straight and go easy on tightening the 10mm bolt back up, but do make sure it's 100% seated or some things won't make contact. I found that out once and the fuel pump wouldn't run.
Modified by Zwicked at 7:40 PM 7/21/2009
I would take a multimeter, set it to the 20 VDC range, and insert 1 probe in each of the 2 connector contacts and run the engine and see if you get a voltage reading before pulling the ECU out.
I would still recommend you first check the Air Reg and the connector cleanliness. It only has 2 bolts holding it on and no gasket. Once it's off, take and hold it up to the light. You should see a sliver of light coming through. Next, connect it to 12 volts and wait about 5 minutes. Now when you peer through it, the sliver of light should be gone. If that's the case, all is well. If not it's gummed up or burnt out. They can gum up in the closed position and not allow high idle when not at operating temp.
Did you run o2 diagnostics as you mentioned? I remember when mine were bad it idles poorly and smoked a lot, not that it stalled though. Still worth running the diag to be sure. It's nice to have everything confirmed working and in spec to make the search of faulty items easier.
I think the auto ECU can be used in a 5 speed but not the other way around.
Removing the ECU is the same as disconnecting the battery as far as wiping anything out and relearning goes. No biggie.
Disconnect the battery before removing the ECU connector. The ECU has 3 bolts holing it down, and then you can get at the connector which has a 10mm bolt holding it in. It needs to be unscrewed and then pull on the connector while doing that. I would run a piece of wire from the AAC plug to ground and use a multimeter or continuity tester just to prove out that the wiring to the AAC is ok.
When you reinstall the ECU connector, make sure it goes in nice and straight and go easy on tightening the 10mm bolt back up, but do make sure it's 100% seated or some things won't make contact. I found that out once and the fuel pump wouldn't run.
Modified by Zwicked at 7:40 PM 7/21/2009