TPS questions (especially for FSM owners)

[Guest bastaad525]

Okay part of this I've asked before. This is an ongoing debate for myself... about leaving my TPS connected or not, and getting a good idea of EXACTLY, ALL of what the TPS does, or rather, what the ECU does with what it sees the TPS doing.

 

Reason I debate whether to leave it hooked up or not is that there is a light, yet noticeable, stumble or hiccup every time the TPS goes from closed (idle) to open. However, I really dont want to get into figuring out why it's doing that, for the moment, I want to learn more about what it actually does.

 

Now, I was under the impression, that when the TPS is closed, and tells the ECU the motor is idling, that the injectors 'switch over' to a much leaner duty cycle. BUT, I've also read, somewhere, more than once, that it's the opposite, that for some reason, it causes the ECU to run richer at idle. Now, I wouldn't know why either one would be desirable, so I can't make an educated guess.

 

Secondly, and this is the question I really hope someone here who knows or has an FSM can answer: when the TPS first goes open, and the ECU sees that the motor has just come off idle, does that cause the injectors to suddenly spray an excess of fuel just briefly, similiar to the way an accelerator pump does in a carbed car? Does the EFI system from the early ZX's have ANY kind of function like this, to spray excess fuel every time the throttle is suddenly increased? Since the TPS only tells it idle and off idle (and WOT, in N/A cars) I don't see how this would help with accelration from a light cruise, where throttle is depressed slightly, and then suddenly snapped open. So does the ECU just see the AFM opening suddenly and use that as a signal to throw some extra fuel in there?

 

The reason I ask, comes back to that stumble. I was reading an article about the most recent model toyota celicas... apparently they are not programmed with any kind of acceleration enrichment action, similar to the accerator pump mechanism, and the result is that the toyota always has a slight stumble when transitioning from idle or cruise to WOT or whatever. Of course, this is just according to one magazine... I'm sure someone here will say "hey I own a celica and it doesn't do that" heh... but it was just funny to me and seemed to strike a chord... because that would explain some things about what MY motor does.

[TomoHawk]

I forgot to reconnect my TPS once and I couldn't start the engine! So that would be proof that the TPS richens the mix- or something else you need to start the engine.

 

My 280Z will do that too (stumble). When I press a little from a stop, I get a little accel, then a stumble, the the power will come on... I figure tthat's when the switch breaks and you get lean mixture power. But then I don't feel any extra power at WOT, and I figure that because it's already at 3000 RPM.

 

So my final conclusion would be to get back in there to adjust it a little better. Should help out with the mixture being too rich also.

thx

[Guest bastaad525]

Heh that's the funny thing a lot of people have been kinda baffled that my car starts or runs at all with my TPS being disconnected, but it not only runs it runs BETTER! And fires right up every time. It really only seems to affect the idle, and cause that stumble of course, when it's connected. I did adjust it so that it goes open with even the slightest touch on the throttle.

 

Another odd thing I've noticed is that the TPS affects timing pretty dramatically. At idle, with the TPS connected, my initial timing is set at 18* BTDC. As soon as the TPS goes open, the timing retards instantly to about 12-14*, and then starts to advance normally as the revs come up.

 

Still trying to figure that one out....

 

Someone suggested it MAY have something to do with the fact that I'm running an '82 ECU and wiring harness, but using an '81 CAS.