Project84

Its on a 86 N/A. The resistance between teminal A and B is 1K ohms at idles, and just a hair over 5 at WOT. However, the resistence between A and C s a hair over 5k at idle, and it drops down to 1k at WOT. The FSM says it should be 5 +or- 1 between A and C at both idle and WOT. If I adjust it, it changes the resistence to a higher or lower number, but there is still a drop over the A and C terminals when going to WOT. Now I have a few questions.

1. Do I need a new TPS?

2. Is this problem causing my car not to start? I rebuild the motor and the if I put a little oil in the spark plug holes, it will start. I already verified that I got spark and fuel. Compression is low right now but the oil makes it fire right up. Once it idles on the oil, I can't change the RPMs by pushing the gas pedal. It Idles, smokes cause its burning oil, then dies. I should be able to rev the gas to keep it running once it starts right? What would make the TPS go bad? When I bought the car they gave me the receipt for the new TPS and it worked fine. I rebuilt the motor cause it had a leaky water seal.

Any help will be greatly appreciated. I've been trying all weekend to get this car to start with no luck other then using oil, which makes it idle for about 10seconds.

NOTE:I know the FSM says to warm the car up before checking the TPS, but my current situation prohibits me from doing that.

SureShot

The warm up is to pull off the fast idle cam on the firewall side of the TB. I think you can back it off by hand to get the throttle to sit on the idle stop.
Your TPS should sweep smoothly from 1K to about 5K.
Even if it's jerky, contact cleaner spray in the plunger will usually smooth it out.
Anyway it's a minor problem that won't kill the engine.

Idles for 10 seconds? Check the AFM & it's connector..

Project84

fast idle and stuff is removed. TB Mod. AFM is hooked up. What am I looking for when I check it? Also, the TPS moves nice and smooth, its just that the reading across the A and C terminals drop off when the FSM says it should be a steady 5k +or- 1k ohms. Is this why I can push the gas pedal and I get no change in engine RPMs?

Scott 89t2

if you've done the TB mode. then ignor needing it to be warm.

if you rpm's don't change. are your TB plates moving? LOL cable hooked up?

HAILERS

That's a misprint in your fsm.

A-B
Idle position: approx 1K ohm
Full open: approx 5K ohm plus or minus 1K ohm

A-C
Idle position: approx 5K ohms plus or minus 1K ohm
Full open: approx 1K ohm

That's my opinion. Personally I leave the plug connected up, start the engine, put the negative lead of the meter on the battery ground, then shove the positive lead up the back of the green/red wire. Should read approx 1VOLT when set correctly. See the pinouts for the ECU in the manual. It states that at idle the output of the tps should be approx 1volt at pin 2G of the ECU. Same reading can be made by putting the positive lead of the meter up the back of the green/red wire at the tps plug (fully connected up plug)

HAILERS

SOME rebuilds have extremely low compression at the beginning. That means they flood in a heartbeat. To overcome that flooding, make a fuel pump cut switch.

I have seen a tps cause my throttle to not work. Car started at the store. Stepped on the throttle. Nadda. Thought the cable came off. Nope.Thought about it a while, then pulled the tps plug off. Car then responded to throttle input. Drove home. Found the guts/spring inside the tps wasn't shoving the plunger to the extend position. Replaced with another tps.So I say the car should start and run with the tps disconnected, although I think the real problem is FLOODING. Make a switch.

Project84

The throttle cable is hooked up. TPS plunger is spring loaded correctly, and appears to be set to with the correct ohms reading (thanks a million Hailers, I never knew that was a misprint).

So I need a fuel pump cut switch. I can do that, but what am I looking for that will show me when to activate the switch? Do you cut the pump off every so many seconds, or do you listen for the engine to start sounding a certain way? I can experiment with different things, but someone else had also mentioned that they use a switch on rebuilt engines. Obviously others have tried it and it works, so how should I use the switch to get it to work for me?

Again, thanks for the input and the help.

HAILERS

Well, if you go out to the car and it won't start, you'd flip the fuel cut switch to the OFF position. Then floor the pedal and crank the engine. The car should start after a few moments with the pedal floored. When the engine starts, flip the switch to the On position right away. Then drive off into the sunset. You only need to turn the switch to OFF to unflood the engine. The rest of the time it should be ON.

Fingers

I'm sorry to hijack your thread, but I have a question about this very thing that may just solve my misfiring problems.

At idle, when warmed up, the SAFC2 shows 0.750 volts. Although, i can set the tps with the two light method successfully. Does that mean my tps is bad, or is the SAFC reading the wrong wire (full range/short range). And if I tighten the screw, the closest I get is 0.85 volts, and the car runs like a bag of ****, and the idle surges.

Anyways, if anyone can shed some light on this, that'd be great!

jcina7

youd think mazda would have checked something so important in their FSM. its not like the tps controls much...

Project84

Fingers, talk to user evilaviator in the ECU forum. Tuning stuff with a SAFC is different then how you would do it if it were stock.

I won't be able to try the fuel switch deal until this weekend. I'll keep you posted Hailers. Thanks.

Scott 89t2

the LED method is adjusting the narrow range TPS. the S-afc is reading the full range one.

to change the full one. you need to slid the whole tps bracket. then reset the narrow one. which will probably change the full one a bit. lots of screwing around