JerryLH3

iTrader: (11)

I have tried with no success to adjust my throttle sensor. Well, maybe partial success.

The car (1991 N/A) has a "bucking/hesitation" problem at cruise speeds in any gear. Mostly in the 2000-3000 RPM range. Highway speeds (for me around 80 mph, 3000 RPM) are fine. Sometimes, the check engine light will flash. I pulled the codes and have always gotten a Code 18, Throttle Sensor - Narrow Range.

I adjusted and verified idle position voltage for the narrow range at 1 V. It was at 1.3 V when I started. After adjusting that, the problem still persists and a Code 18 is still recieved (and yes, I cleared codes after adjustment).

The service manual states full open throttle should be approximately 5 V. I'm only getting 4.4 V.

Is my throttle sensor basically a piece of junk?

GLHS

Clarify.... The sensor is not holding the adjustment?

Or you get a code, adjust it, get same code is it still in the correct voltage range?

rico05

Sounds like it won't hold adjustment. That means it is shot....Not an uncommon sight (glad mine still worked) This means you eiteher shell out $180 to www.mazdatrix.com, or you buy a used one and hope for the best.

RX4Man

do u have an ociliscope on hand? a scanner and ur meter sample to slowly. an o-scope samples at something like 5 million times a second for the older ones. the newer ones sample at like 20 to 25 million times a second. a scanner samples about every 1.25 seconds and a digital multimeter samples at about 4000 times a second but only updates the screen about 4 times a second. but if u do get ur hands on an o-scope, u need to have the car on but not running. u can get a wiring diagram of the tps and use the positive lead to back probe the signal wire and the negative lead to back probe the ground wire. there r 2 test u can do. a fast sweep and a slow sweep. set the o-scope to 1 volt divisions and 200 ms (millisecond) divisions. there should be about .25volts to 1 volt at idle for the lowest and about 3.5 to 4.8 volts. just keep cycling it. u should see a serious of bell curves. now for the fast sweep. u need to set the o-scope to 1 volt divisions and 1 ms divisions. this time u need to snap the throtle quickly. there shoudl be a nice ell curve. but if there is a bell curve with 2 spike that go downon each side of th4e curve at the same point across from each other, then ur tps is no good. it doesnt take that long to test but it requires alot of stuff that u have to know. haha. most of the numbers that i stated are general references not exact so u might have to make it read into the micro seconds or maybe to 2 ms. but the volts should be ok. good luk but for the most part i think ut tps is bad if it doesnt work in just that range. hope this helps every one here. late

RETed

This is why I measure resistance at idle and WOT - what is the resistance reading at WOT?&nbsp Anything over 6k-ohms will cause the ECU to barf...


-Ted

JerryLH3

iTrader: (11)

I'll have to go out tomorrow morning and check.

Offhand, does anyone know which two wires I need for measuring resistance for a 91 N/A throttle sensor? I was using a wire run from Terminal 2F of the ECU from my test connector (see https://www.rx7club.com/forum/showth...threadid=18000) to measure the voltage.

I don't have an oscilloscope, but that's great information to have. I'll remember that.

Blowtus

4.4v shouldn't be a problem at wot afaik, but if you're bucking around it sounds like the tps is dodgy and dropping out every so often. Mine did the same thing a while ago. If you get a dmm onto the throttle sensor input of the ecu while driving you can watch the voltage go smoothly up and then see it drop / go crazy as the car starts bucking. replace the tps situation basically...

Charlie