1990 Icsv - Toyota Nation Forum : Toyota Car and Truck Forums

RATTLER333 · 05-28-2010, 04:19 PM

Can any one tell me how the Idle Control Speed Valve should be adjusted on my 1990 Celica GT with a 2.2 5SFE engine. When the valve is not energized in a static position, what should be the position of the metal tab (pintal) inside the valve that controls the opening? Should the opening be fully open, fully closed, or 50% open / closed? When the valve is energized, should the valbe be able to be fully closed, and fully opened? This is a 3 prong electrical connector with an electro magnetic control. Thanks, Rattler

93celicaconv · 06-06-2010, 08:12 PM

Are you talking about the IAC (Idle Air Control) valve? Your 90 2.2 5S-FE does not have an Idle Speed Valve!

What is the problem you are trying to correct?

The 90 & 91 Rev. 1 5S-FE's also had an manual idle adjustment screw. If you follow the service manual, when you disable the IAC valve, you should adjust this manual screw so that you obtain a specific RPM. Then when you enable the IAC valve, your engine idle speed should be about 700 RPM. Is the problem your idle speed?

RATTLER333 · 06-07-2010, 08:09 PM

My Haynes manual calls it a ISC valve (Idle Speed Control Valve). It it mounted to the underside of the throttle body with 4 screws. It has 3 ports on the bottom, 2 of which connect to the cooling system, and the other to vacume, and has a 3 prong electrical connection. When I do an ohm test on the 3 prong electrical connector, I get values whithin specs called out in the manual. The vehice just does not want to idle, and appears to be miss firing. Listining to the exhaust, it sounds like the head gasket is blown, but the compression test results show otherwise. I want to believe that the problum is related to an engine control device, but have not been able to find any that are failing.

93celicaconv · 06-07-2010, 08:20 PM

OK, then that is what Haynes calls it. The Toyota Shop Manual calls it an IAC (idle air control) valve. By your description, we are referring to the same part.

As far as I know, there is no adjustment to the IAC valve itself. The 1990 5S-FE does have an idle adjustment screw to set the idle speed properly. Your Haynes manual should contain the information on setting the idle speed (you have to jumper 2 connections on your diagnostic connector to do this), then turn your idle adjustment screw on the throttle body to obtain the required engine RPM.

However, your engine should not be misfiring, even if the engine idle speed is too low or too high. Does the engine act like it is misfiring when the engine speed is raised?

RATTLER333 · 06-08-2010, 07:11 PM

The engine does not missfire when the rpm's are raised. After dissembling the IAC from the throttle body, I can see where you can remove 2 screws from the backside of the shaft, (allthough they are painted with red paint from the factory, which tells me this is a tamper issue with the emmisions inspections). With the screws removed, you can adjust the shaft, which directly relates to the metal tab either fully opening / closing the internal port of the valve. This opening in the internal port of the valve is what I don't understand how it should be adjusted. The way it was when dissembaled, before removing the 2 screws, when energy is applied to the switch the port would not fully close. Should it?

93celicaconv · 06-08-2010, 07:22 PM

I guess I would ask why you didn't leave the IAC valve alone, and just adjust the idle speed adjustment screw within the throttle body to raise the engine RPM's just a little to eliminate your issue.

I don't know much about taking the IAC valve apart to make adjustments. I haven't done that before.

RATTLER333 · 06-08-2010, 08:30 PM

I did adjust the idle speed adjustment screw within the throttle body, before dissambeling the IAC, but it did not resolve the idle issue. I am wondering now if there is an issue with one or more of the engine system management switches / valves / controls. Since all of the componets that I have tested, showed ok for either ohm or vacume values, I have to think that one or more of them is actually not operating completely normal. I want to elimaniate that possibility before I replace any of the componets in the system. I did not change the initial setting of the IAC, I just looked into how it could be adjusted. If the IAC was manufactured with the intention of not being adjusted, then I would think that there would not be any access to the adjustment? Could the ECM be giving specific engine controls incorrect values, making them appear to fail, and if so would there be a code set in the internal memory, not necessarly showing up in the check engine syatem?

93celicaconv · 06-09-2010, 06:21 AM

Thinking of basics, there is air, compression, fuel, ignition, and the timing of all, that makes an engine run.

On the air side, is the path for air going to the throttle body unobstructed? Good air filter, no debris caught in the air pickup at the front of the car?

On the compression side, have you checked you cylinder compression at all? If so, what are the exact compression pressure values per cylinder?

Fuel, you have done some work by changing a couple of injectors already without a change in the symptoms (that is pretty hard to do on a 5S-FE, with that intake manifold in the way, isn't it?). It would be good to get a fuel pressure value at the fuel rail, if you can. Although I have a feeling this isn't where your problem is, but it would be best to test it to make sure it is not the source.

Timing; have you made sure that your mechanical (crankshaft to camshaft) timing is spot on, that your timing belt hasn't jumped a tooth or two? Also, have you checked your ignition timing following the proper procedures?

Just some thoughts on where I would be checking things.