Gen 1: Location of Idle-Up Relay?

[Mister O's MR2]

I have done two searches of this forum and am unable to find the answer to this question:

Where is the idle-up relay for the a/c located on the Gen 1 normally aspirated model with the 4AGE engine and a manual transmission?

I have a 1987 model, purchased new in November '86.

The closest I got was a post with a link for the location on a Gen 2, but I get the message: "Bandwidth Limit Exceeded" after clicking on the link.

I went to the local dealer, and me and the parts guy tried finding it in my engine compartment while looking at the diagram in my official Toyota shop manual for the MR2.

I was able to locate and test the VSV on my own (parts guy says that stands for 'vacuum service valve') and it tests OK.

Please help if you can. It's summer and my engine won't run at idle with the a/c on because the idle-up feature doesn't work.

Thanks in advance.

[toyotaspeed90]

it's by the battery tray, more so on towards the rear -- has a large white plastic screw on it, one electrical connector, and 2 larger vacuum lines....

it isn't uncommon for these to not be bolted down and dangling somewhere

[Mister O's MR2]

Originally Posted by toyotaspeed90

it's by the battery tray, more so on towards the rear -- has a large white plastic screw on it, one electrical connector, and 2 larger vacuum lines....

You are referring to the VSV, which I located and tested. The idle-up relay (which I am unable to locate) is another component. Per the shop manual instructions and diagram it has a 4-prong connector, but is unclear as to its location.

Thanks anyway.

[toyotaspeed90]

I doubt it has an actual/specific relay for it....

most vsv's and switches that toyota uses, if they have power, are turned on via the CSI, which is the main relay that turns most engine related components/sensors on. The power wire is generally a black with red stripe.....

[Mister O's MR2]

Originally Posted by toyotaspeed90

I doubt it has an actual/specific relay for it....

I am just going by what the service manual says: the manual transmission version of my model has an idle-up relay.

Maybe that is why I cannot find it!

If there is not such a relay on my vehicle, and if the VSV tests OK, any suggestions as to what my next step would be?

The last time I had used my a/c the idle-up feature was working. But not now.

The service manual doesn't go into how to use the adjustment wheel on the VSV.

[GeoffBooth]

If I remember rightly it's behind the passingers side kick pannel. Think a couple of assosiated fuses reside there as well. I've got a problem with my AC. No power to the pump. Messed with it on and off for years but can't find the fault. The idle-up works though and you can hear what sound like the relay operate. I'll check it out in the morning to see if sound comes from behind the kick pannel.

Would like to hear from anyone with any ideas what could be wrong with mine.

[GeoffBooth]

Yes thats where the click comes from. behind the offside kick pannel. Think theres some bits behind the glove box aswell.

[Mister O's MR2]

Originally Posted by GeoffBooth

Yes thats where the click comes from. behind the offside kick pannel. Think theres some bits behind the glove box aswell.

I checked behind the passenger kick panel today. There is a square-looking item there that may be a relay, but the drawing in the service manual (the Big Green Book) indicates that the relay is round.

Anyway, I was unable to pull it out easily and, since I couldn't see it well and it was difficult get a good purchase on it, I was afraid to apply too much pressure and break something.

I did find a couple of other round relays inside the front trunk on the passenger side, but one was marked (inside the cover) as "A.C.FANNO.3" and the other "FANNO.1".

(There was also a square relay marked "A.C.FANNO.2" in this area. How many fans does the A/C have?).

Could one of these 'Fan' relays actually be the 'Idle-up Relay'?

[GeoffBooth]

The relay I referred to behind the pass kick panel is the heater relay. There is also a fuse there. This does click when I activate the AC button and the engine idles up. But that don’t mean much.
The relays behind the glove box are for the head lamps.

Looks like the Idle-up system is powered by the 10A AC fuse. The only control looks to be the VSV.. How did you check that? I don’t see much else that would fail.

The book says there are 2 different types. One with the big screw and one without.
Either one:

Make sure all accessaries are turned off. To check the VSV battery voltage. Use a volt meter to verify that there is battery voltage during cranking and for 10 seconds after the engine is started. A test light would probably work just as well.

I would also assume that you should also get power with the engine and AC running.

If that checks out, remove the VSV from the car. You should not be able to blow threw the inlet to the outlet. Apply Battery voltage and you should.

If that checks out. See if you have a vacuum to the thing.

The VSV is probable just a electrically operated vacuum switch. I’m sure you can think up many ways to check it’s operation just by removing the pipes to see if it’s sucking when it should. If there is no power to the thing. Apply power and earth directly from your battery with everything running and see what happens. Be sure to disconnect the harness first. You may have a bad earth.
Another idea would be to bypass the switch by joining the inlet and outlet just to see if it idles up.

[Mister O's MR2]

Originally Posted by GeoffBooth

Looks like the Idle-up system is powered by the 10A AC fuse. The only control looks to be the VSV.

The BGB states that there is also a idle-up relay in the manual transmission model.

If that checks out, remove the VSV from the car. You should not be able to blow threw the inlet to the outlet. Apply Battery voltage and you should.

That is what I did, following the directions in the BGB, page AC-43. Tests OK.

If there is no power to the thing. Apply power and earth directly from your battery with everything running and see what happens. Be sure to disconnect the harness first. You may have a bad earth.
Another idea would be to bypass the switch by joining the inlet and outlet just to see if it idles up.

I'll try that next, thanks.

[Mister O's MR2]

Now I am really confused.

I thought that the Idle-Up Relay controlled the 12v to the VSV (vacuum service valve), but what happened today makes me think that there is more to the idle-up circuit than what is stated in the service manual (BGB, or Big Green Book).

I unplugged the electrical connection from the VSV and connected my VOM to it. With the engine running and the A/C on, I get 12v to the plug for a
while, then I don't, then I do again. Even though the plug is OFF the VSV, the idle speed is affected (goes up and down) with the change in whether or not there is 12v at the electrical plug. I also hear a relay clicking somewhere in the engine compartment whenever the 12v is turned off or on.

When I connect the two vacuum hoses together (A/C off), the idle speed is affected--but not in a good way. The engine barely runs (like there is a vacuum leak, DUH!).

If I plug the end of the larger of the two hoses with my finger, the engine idles normally.

I am nearing my wits end .

Also, the fuse block cover in the left side kick panel states: "Heater-ac fuses are located behind assist kick panel".
Does that mean the passenger (right) side kick panel?

[GeoffBooth]

[B][B]I unplugged the electrical connection from the VSV and connected my VOM to it. With the engine running and the A/C on, I get 12v to the plug for a
while, then I don't, then I do again Even though the plug is OFF the VSV, the idle speed is affected (goes up and down) with the change in whether or not there is 12v at the electrical plug. I also hear a relay clicking somewhere in the engine compartment whenever the 12v is turned off or on.

When I connect the two vacuum hoses together (A/C off), the idle speed is affected--but not in a good way. The engine barely runs (like there is a vacuum leak, DUH!).

If I plug the end of the larger of the two hoses with my finger, the engine idles normally.

I am nearing my wits end
Your not at your wits end lad, your actually getting close to solving the riddle. All these actions and reactions are telling you something..

Lets take a look at this logically and without the book..

The AC system cycles on / off to keep up a pressure. The idle-up system is to compensate for the torque created
when the AC clutch is engaged. (That is the clicking you hear in the engine bay) ether a relay or the clutch cycling on / off. There for the Ide-up system will activate on / off (that’s why you get 12v at the plug then nothing) this would tell me the electrical side of the Idle-up system is working fine. So you can put the relay idea to the bottom of the list.

The VSV switch then activated will allow the vacuum through the switch, up to the throttle body to increase the RPM to compensate for the torque of the AC when cycled on. The big screw (if you have that one) must be to regulate the amount of vacuum going through the switch hence the level of throttle up.
When I connect the two vacuum hoses together (A/C off), the idle speed is affected--but not in a good way. The engine barely runs (like there is a vacuum leak, DUH!).
When you connect the vacuum hoses together this would allow the full vacuum and I would expect the engine to throttle up to a high level without the switch to regulate the vacuum. But this does not happen.
The engine barely runs (like there is a vacuum leak, DUH!).
Follow the line up to the throttle body and check for cracks and I mean really check. Then disconnect the line from the throttle body. With the engine running and the AC on and clutch engaged ( when there is power to the VSV) you should have vacuum at that end, right.
If the vacuum is present, sufficient and cycles on/off with the AC then the fault is in the throttle body. Probably gummed up in some way.

Let me know the results.

[Mister O's MR2]

The VSV switch then activated will allow the vacuum through the switch, up to the throttle body to increase the RPM to compensate for the torque of the AC when cycled on.

This confuses me. I have found that the vacuum line from the throttle body already has the vacuum on it.

When you connect the vacuum hoses together this would allow the full vacuum and I would expect the engine to throttle up to a high level without the switch to regulate the vacuum.

That is what I thought would happen too.

Then disconnect the line from the throttle body. With the engine running and the AC on and clutch engaged ( when there is power to the VSV) you should have vacuum at that end, right.

I did this test a little differently. I left the line connected to the VSV (at the fitting indicated as 'B' in the BGB, page AC-43) that goes to the throttle body, but disconnected the other line (indicated as 'A') at the VSV. Then I started the engine with the A/C off and felt for vacuum at 'A'. I get a 'flutter' of vacuum at 'A'. Then I turn on the A/C and felt for vacuum at 'A' and now I feel full vacuum. This indicates to me that there is a little leakage at 'A' when the VSV is in the 'OFF' condition, but that it opens fully when in the 'ON' condition.

I also thought of something else that may have an effect. About 1½ years ago I installed a K&N FIPK. I reused the 90º 'elbow' fitting from the stock installation and have the other hose from the VSV connected to a fitting on it. I think that this 90º 'elbow' may have been installed after the air flow meter in the stock configuration, but now is installed ahead of the air flow meter (it's been a while, so I can't remember). If so, this could be the cause of my problem.

I seldom drive this vehicle (less than 1,000 miles per year) and so have little opportunity to use the A/C. This may, in fact, be the first time I have used the A/C since the installation of the FIPK!

Note a possible error in the BGB at the bottom of page AC-43, Item 3(b): the diagram indicates that there should be no continuity between terminals 3 and 4 on the Idle-Up Relay when 12v is applied across terminals 1 and 2, but the narrative indicates that there is continuity.

[GeoffBooth]

Ok. What a trip this is but good for the education. I don’t have access to the BGB, only Haynes. Been studying this all night and couldn’t wait for it to get light so I could run a few test on my Idle-up system.

Firstly, I assume you have the VSV with the large screw. In Haynes (A) is the Bottom horizontal connection to the underside of the throttle body and B (vertical Top) to the air intake.

Here’s what happened: In the original set up B was connected to the air intake in between the air flow sensor (AFS) and the throttle body. When I disconnect B the engine stalled out. This is probably due to reducing the air flow through the AFS closed the flap which in turn shuts off the current to the fuel pump. This will not happen on yours because you are connected before the AFS. To my surprise when I disconnect A at the Throttle body there is also vacuum and the engine stalls out unless you plug the throttle body with your thumb. When plugged there is no idle-up when reconnected there is.

Therefor I deduce the VSV when engaged balances the vacuum between the two. With installing side B to the other side of the AFS upset the balance of the vacuum which can probably be adjusted via the large screw if there is enough vacuum created, installed in that location. In my case turning the screw in (clockwise) increased the RPM and so on.

Please let me Know the outcome.

It's a good idea to run you’re AC few minutes every time your start the car. They do mess up otherwise.

[Mister O's MR2]

Originally Posted by GeoffBooth

Firstly, I assume you have the VSV with the large screw.

Yes, I do.

In Haynes (A) is the Bottom horizontal connection to the underside of the throttle body and B (vertical Top) to the air intake.

In my installation, 'A' (the fitting parallel to the adjustment screw) on the VSV is connected to the 'elbow' fitting that, in my case, is installed before the air flow sensor. 'B' (the fitting 90º to the adjustment screw) is connected to the fitting below the throttle body.

It may be a bit confusing because the diagram of the VSV is shown upside-down of its actual orientation when installed.

With installing side B to the other side of the AFS upset the balance of the vacuum which can probably be adjusted via the large screw if there is enough vacuum created, installed in that location. In my case turning the screw in (clockwise) increased the RPM and so on.

I tried turning that screw in both directions in my installation, but it had no effect.

I am going to reinstall the original intake system (or re-do my FIPK installation) to get the fitting back between the air flow sensor and the throttle body.

I'll post an update here.