Yesterday I started having rough idle problems after the engine had warmed up. I read that the TPS sensor can fail and cause this or it might need to be adjusted. Any you 1st gens had this problem?

Ive got new spark plugs, dist cap and rotor (5k miles on 'em) so it's not that. Doubt it's the plug wires but that's also a possibility.

Just curious if anyone had any thoughts. I'm taking it to JP IMPORTZ anyway (coolant leak) so I'll know for sure hopefully this weekend.

 

I remember finding a spec sheet on how to test the tps to see if it's working. I'll try to find it later on when I get back from school this evening. If I can't find it, I'll take a picture of the sheet that I printed up.

 

I'm having the same problem with mine. I got two new ones, but I haven't adjusted them yet.

 

So are there two sensors? I only know where 1 of them is. Does yours do this to?

If I let it idle for 30 seconds or more it is really sluggish when I give it a little gas to start moving, like it is really bogged down, but this does not continue for too long until it seems fine, and then I have to stop again...

If I just do a real quick stop and go it is much easier to get moving, though.

 

Guys, if your cars have many miles on them, its a good idea to check the ignition timing also. At 200k my car lost 2 degrees of ignition timing somewhere. The bolt had never been out of the distributor before either. So, the system lost timing due to normal wear over the years. You wouldn't believe how confusing 2 degrees is to an ECU.

 

This may just be coincidence, but I just got the O-ring on the distributor replaced and now the car seems to pull harder in the upper-rpms. I think that when the mechanic put back the distributor, he corrected the timing.

The cars with traction control have a second throttle which has its own TP sensor (they're called the sub-throttle and sub-throttle position sensor, respectively). If you have traction control, the first throttle is the sub-throttle.

As far as checking the TP sensor goes, you'll need an ohm-meter with aligator clips. On the sensor, there are four pins. The top one is the ground (keep the negative side of the ohm-sensor connected to this pin). The three other pins are the ones where you'll connect the positive side of the ohm-sensor to. Turn the key so all the lights in the dash turn on but don't start the car.

Connect the positive side of the ohm-meter to the second pin. The second pin must produce .5k ohms or less. This pin tells the computer to idle.

The third pin ranges between 2.4 - 11.2k ohms. Slowly open the throttle so you can see if the ohms climb from 2.4 to 11.2k ohms (it must climb at the same rate that you open the throttle). This sensor tells the computer how wide the throttle is open.

The fourth pin ranges between 3.1 - 7.2k ohms. Do the same procedure as the third pin to make sure it climbs from 3.1- 7.2k ohms as you slowly open the throttle.

These specs also apply to the sub-TP sensor, but the pins are upside-down (the bottom pin is the negative, etc.). If any of the readings are off, the sensor could be bad. Maybe the sensor is not adjusted properly.

You can adjust the sensor by loosening the two phillip screws that hold it in. Using the ohm-meter, attach the negative wire to the top pin. Attach the positive to the second pin. Move the sensor counter-clockwise until it stops. Now gradually move the sensor clockwise until the ohm-meter deflects. Now tighten the screws.

Now recheck the pins again to make sure the ohms are in the proper ranges. If they still aren't, the sensor is most likely bad. I obtained this information from a schematic, number EG-238 to EG-249.

 

Woah. Thanks for the info! What DON'T you know about our cars? lol.

I don't have the TC so that's one less sensor to worry about I guess.

 

You should also clean your throttle-body, sometimes the gunk builds up around the throttle plate and causes the idle to be low or rough. Just spray throttle cleaner inside the throttle body to clean it up.

Let us know what happens

 

Oh I did that 5k miles ago as well when I did the spark plugs and everything else.

 

Heh. It was water in the engine. I was wrong it isn't just idling rough it's missing when warmed-up.

Last time it was washed was last Monday at the dealership during the oil change (even though I said please do not wash).

Be careful washing your cars - or letting others.

 

I feel your pain Pianoman72. I fought the same battle with my GS for about 2 weeks until I figured out that the plug wires were leaking fire inside the valley. Mine had coolant on them from a leaky coolant hose on the throttle body. The plug wires have very thin insulators on them. Any kind of water contamination will cause them to leak fire terribly. I suggest that everyone go out and look for a larger set of wires with thicker insulators. Sometimes they are hard to find at a good price for the GS, but don't forget that you can use aftermarket and OEM wires from the Supra with the 2JZGE engine. Later guys....

 

Cool, I'm glad to hear your engine is fine

 

subscribing im having tps problems so I need info on adjusting the sensor