Truck Tech


Hi Roger;

My A/C wonít idle up w/ 3vze engine.My A/C works great, still R12, and blows ice cold. It just drops at idle with the A/C on, like to around 500 to 600. I adjusted the A/c idle-up Vacuum Switching Valve (VSV), all the way in and out, but no change in RPM. The connector to the VSV is getting 13.something volts with the A/C on, zero with it off. I changed the VSV with the one from another motor, no change. Do you have any ideas?I did search!Thanks; Gregís Toy



Hi Greg;

It is very common for the vacuum fitting that feeds the idle-up VSV to get clogged. Make sure you are getting vacuum to the VSV so that is has something to switch. Also, quick test of the idle-up valve and vacuum source is to bypass the VSV and connect the vacuum hose direct from the intake to the idle-up valve.




Hi Roger;

I was driving to work this morning and my oil pressure gauge dropped to nothing.I went to the book and the diagram.Needless to say is a bit crappy, you wouldnít happen to know where a good website with an engine cut away for a 1986 4runner 22re and the placement of the oil pressure switch would beÖ. I would appreciate it.

James Luce



Hi James;

Youíll find the oil pressure sender right by the oil filter on the passenger side of the engine.There is a panel inside the wheel well that can be removed for easier access.Likely the wire came off the connector which is under the rubber boot that covers the sender.



(a reply from James)

Hi Roger;

Thanks.That was an easy find when you look on the right side of the engine.The book I have shows the switch on the driverís side of the engine.

Thanks; James


Hi Roger;

I have read your web page with major interest.I am really hoping you can help me with my problem as a favor.

I am Ďstumpedí with my 1990 4runner 22RE engine problem.Any help will be appreciated.

Here are the symptoms:

1.†† Idles fast (2000 RPM) when cold and the idle adjust does not reduce it any further

2.†† Idles at 1000 RPM when warm

3.†† Poor acceleration (timing light shows timing advances very slowly)

4.†† Timing is at 10 degrees After TDC (will not idle at 5 degrees BTC)

5.†† EFI fuse shows current even when vehicle has been turned off (I used a voltmeter to test the fuse connections)

6.†† A blue puff of smoke comes out of the exhaust when engine starts. Valves and rings are in good shape

7.†† Loud pinging sound in the engine

8.†† Knock sensor is not working (wire broken)


I had replaced the head gasket some time ago. I might have misaligned the timing chain at the crankshaft by mistake. So I move the chain by 1 link and the timing improved. I did not want to move it any more in fear that I will damage the valves.

Is there a way to determine if the camshaft is at the right position when the crankshaft is at TDC (canít use alignment mark on chain) without pulling the timing cover?Does the knock sensor affect the timing and cause poor acceleration when it is not working?

Hope you can help. Thanks in advance!Insha Khan



Hi Insha;

With the variety of problems you are describing, I would suggest going back to basics on the engine and double-check a few key items:

Re-check the timing chain, 0 BTDC on the crank, dimple on top, for pictures and details, see my web page:

The knock sensor affects timing, thatís what it does, fix it:

Check the Throttle Position Sensor (TPS):

This will affect your base timing, if the idle/timing does not change with application of the timing check jumper:

Then your TPS needs adjustment.

Check the Air Flow Meter (AFM):

The 22RE Electronic Control Unit (ECU) is supposed to pull some small current when the ignition is off in order to maintain the stored settings in its internal memory.

Hopefully you will find the cause of the problem.And donít just stop if you find one problem, there may be multiple issues.




Hi Roger;

I have problems with my starting system. You know the one, that famous CLICK!I have replaced the contacts and even made sure that they are level and make contact with the plunger surface. Still the problem persists.

I have performed the continuity test (with & w/o 12volts applied) on the starter relay. This test verified, according to the Toyota manual, that the relay is OK. I have over 13 volts battery voltage at the battery, relay and at the starter. Now, the interesting thing is this, my ignition key is severely worn but it only turns the ignition switch tumbler, full of contacts, right?The click I hear is at the starter relay and no sound coming from the starter solenoid when this happens.Something else is funny, at one point while investigating the ignition switch, I sprayed the contacts w/ contact cleaner and I no problem for quite sometime. Another thing is that this was happening only in the mornings after the vehicle had sat overnight. But it did not happen all the time. It was sporadic. Now the last couple of days it is more often than not. Days have been hotter. Should this matter?

This has even happened with new starter installed, so I returned the starter. I am lost, canít think of anything else to do.Can you make any suggestions?Can the Hot-Shot starter relay kit be utilized even though I have a factory installed starter relay?

How would bypassing the original relay affect the system and would it foul up the ECU?Thank you for your time. I would appreciate your suggestions.

Yours truly, Gordon Carpenter††



Hi Gordon;

I think you will find all the answers at the bottom of my starter repair page.In short, the problem is the way Toyota wired the starter relay (in the vehicles that even had a starter relay).While there is a relay that is turned on by the ignition switch start contacts, the power that the relay sends to the starter solenoid comes through the very same ignition switch contacts.So, the relay does nothing to relieve the load on the ignition switch.For a few repair and upgrade options (one of which you referenced), see:





If you are searching for, building, modifying, or maintaining a Toyota 4WD mini-truck (Pickup, Hilux, 4Runner, Surf, or Tacoma), send your Truck Tech questions to Roger Brown at <>. Iíll try to answer your questions with authority! And please be sure to provide a valid return address in your e-mail if you want a faster reply.