I have a dumb TPS/Timing question
 

I've been reading all day and I can't find an answer.

When I time my 22RE, I short the connector and the idle drops which is good.

However my question is when the connector is shorted the computer shouldn't be advancing the timing at all correct? When I rev the motor slightly over idle with the connector still shorted I can see the computer (or something else?) advancing the timing, but isn't it not supposed to do that?

/dumb question :dunno:

Hey Xylicon,

I am not positive but I could see two things happening here.

first, when you rev are you sure the jumper is shorting the terminal, it might be losing contact thus letting the ecu adjust the timing.

second, if the terminals are still shorted out when you rev, it might be that the ecu is detecting fuel and air increase in the engine and trying to adjust based on that.

Like I said, it's just a thought, It would makes sense that there should be no timing adjustment when the terminals are shorted but other sensors could be sending singnal in a round about sort of way, so techinally the terminals are shorted but timing is still be adjusted by your reving ie more fuel and air...

It may be "other sensors" helping it to rev as OrRunner says and you may only notice a lack of advance (and power) if you actually drove it and put a load on the engine.

When you time your motor without the jumper you'll be timed at about 12-13* BTDC. The jumper is supposed to advance about 8* so you can time it without the ECU doing anything to it. It is there to eliminate the possibility of faulty wiring or a faulty ECU. The timing is purely mechanical at this point.

However, if you rev up your motor the ECU will in a sense ignore the jumper and retard the timing as if the jumper isn't installed. Someone correct me if I'm wrong here but it does this to protect the motor from detonation due to bad timing.

The timing drop only occurs when the throttle is at idle AND THE TPS IS GROUNDING IDL TO E2. If the tps is faulty, or not positioned properly, or throttle is not at idle, there will be no timing/rpm drop.

svdude I think you meant "advance the timing" not "retard the timing", lol. Going from 12 to 5 when jumper set is in the direction of retarding, not advancing.

Probably what happens with the drop is that the jumper causes the ecu to stop sending an advanced timing signal on IGT to the igniter, and when that happens, the igniter will use the signal from the signal coil in the distrib which is directly on tdc and has no advance. But when you open the throttle, IDL no longer grounds to E2 and the ecu must resume sending the IGT signal.

The 3VZE has a different ignition system and the signal coils don't connect directly to the igniter as in the 22RE system. I've never noticed an rpm drop on mine and I think that's normal for the motor. But on the 22RE you have to make sure the rpm does drop when you set the jumper, and if it doesn't drop, the TPS is the first place to check.