ok, i'm sure everyone is tired of my TPS questions....but here's one more...

when i bought my T2, it ran and drove fine. but 2 hours into my 15 hour trip home, it started with the bucking and hesitating...and for the remaining 13 hours it just got worse. i installed a 91 jspec TPS last week and now its great again...****, even better than before...

my quesiton is: can the TPS just go bad over the course of 2 hours??? or would something trigger it to go bad? when i took the old one off, i noticed 2 of the wires were sort of frayed. so maybe the heat from the IC over time caused it to mess up? or does the TPS recognize when you are "highway" cruising for 15 hours and decide on its own to screw you??? LOL

 

c'mon TPS gurus

 

I think so Erik, mine works fine for the first 30-40 minutes of driving. After that it turns to **** and starts acting up.

 

It probably did that because your TPS setting isn't perfect and the water thermovalve screwed it up.

The water thermovalve opens and closes depending on the temperature of the coolant. So if you set it when it's only half open, the car is only going to run right when the thermovalve is half open. If you set it when it's all the way open, like it should be, the TPS and throttle and all that crap won't play any tricks on the ECU and the car will run good.

So when I set my TPS, I always have my water thermovalve disabled by removing the spring on the fast idle cam linkage. That way the thermovalve can't adjust the idle and the car is always in a "hot" idle position.

I had this problem with my car when I first got it. I would get the TPS set "perfect". The car would run great, all the way to the interstate. A couple hours later when I got off the interstate the car would be back to running like ****.

 

but won't this thermovalve be open once the car is up to operating temperature (and just stay there)? is this why they say warm the car up before you check and adjust the TPS?

 

Yes, but you're going on the assumption that you know that the thermovalve is opening all the way, which it may not be. If it isn't, it makes it incredibly difficult to get an accurate TPS adjustment, and in my experience it's impossible.

So, by disconnecting the spring and wiring back the fast idle cam you eliminate the only variable that can directly adjust the throttle plates that you have no real control over. This makes it easy to get a good TPS setting since the throttle body is now locked in a permanent (reversible) state of warm idle.

I just left mine disconnected. The car runs like **** in the morning because of it, but it only lasts a few seconds.

The reason it'll run like **** is because there's a water temp sensor on the bottom of the radiator that sends a signal to the ECU. If the water is cold, the ECU richens the fuel mixture a bit. This in addition to the thermovalve on the throttle body that adjusts the throttle plates works kinda like an automatic choke system.

When you remove the thermovalve's ability to do it's job the ECU still richens the mixture because of the signal it's recieving from the sensor on the radiator, but it's not getting enough extra air through the throttle body to perfect the mixture the ECU expects, so it runs crappy.

 

hey Mykl.....do you have a pic of the thermovalve, and the fast idle cam screw? i'm guessing they are in the same spot. probably behind my intercooler.

 

I wanted to take pictures the last time I had the throttle body off, but I didn't have a camera.

It's really easy to spot with the TB off though. Just look on the back of the throttle body and you'll see a little screw lookin' thing that's touching a flat surface. This flat surface is the thermovalve. You'll notice that the flat surface, or rod, or whatever, will actually push down on that screw. The screw is attached to the linkage for the fast idle cam. On a separate linkage there's a roller, that rolls along the fast idle cam. When the rod in the thermovalve is fully retracted the roller will sit on a portion of the cam that causes the throttle plates to be opened slightly.

If you take the throttle body off and play with it some you'll see exactly what I'm talking about. A manual of some kind will help you identify all the parts. Try the '88 FSM on www.iluvmyRX7.com . It may not be exactly the same for your car, but it will be very similar.

 

thanks! ...yeah, i've got a copy of the 89-91 shop manual, so i guess i'll have to look thru that and find it. but is it manditory to take the whole throttle body off to disable the thermovalve?

 

The thermovalve may go under a different name in the FSM, keep that in mind. It shouldn't be too difficult to figure out though.

Yeah, it's impossible to get to all that stuff with the TB still on the car. It isn't difficult to remove though. Also, by taking it off and playing with the linkages and stuff you get a better understanding of how all the **** back there works.