TPS and idle

[thegary]

Hi there everyone. I have been for some time now trying to get my car running more smoothly. 91 240SX HICAS. Here is what i have replaced.

1. Seafoam (gas, oil and intake)2. new O2 sensor3. removed AIV4. New plugs and wire5. New cap and rotor6. cleaned throttle body7. new feul filter8. replaced AICV (acc) EXPENSIVE ONE!

Replacing the AICV fixed my idle dropping off to nothing and almost stalling.

When i try to set my idle, I disconnect the TPS and then race the engine a few times letting it fall to a idle position, but i cannot get it to come down to 650. The lowest i can get is about 1100. When i plug the TPS back in the idle is about 800-900. Any thoughts on how i can get the idle set properly? I have been doing all of this to improve gas milage and also to fix the fact that i have to press the gas pedal to start the car. The odd time it will start first turn, but thats about 1 out of every 20 starts. Also my power seems quite good when the engine is cooler, but i have noticed with the warmer wheather, when its about 15cel. out, then engine when warm is lacking power. Any thoughts.

Thanks ......thegary

[pr240sx]

You may have an air leak in the intake manifold area or the throttle plate is not closing clompletly.

[thegary]

I have cleaned the throttle and it does close all the way from what i can tell. How do i go about finding out if I have a intake leak?

thegary

[niznos]

You didn't actually say what you were doing to set the idle. Are you moving the TPS to fix the idle? If so, you need to reset the TPS back to its correct position, then use the screw in the AAC. If you were already doing this then disregard this post.

[thegary]

I adjusted the screw on the AAC, after i had unplugged the TPS. What sort of adjustemt can be done to the TPS?

thegary

[bokinsmowls]

!NOOB WARNING!:

aac?

[niznos]

Two quick checks for TPS both with engine off:

1. Disconnect TPS and use a multimeter to check for resistance on the lower two contacts on the TPS side of the connector. You'll most likely need a helper to move the throttle linkage. You should see resistance change as the throttle opens and closes. If not you'll need a new one.

2. Disconnect the connector that is on the actual TPS and meter the lower two contacts of that conn. for continuity. With the throttle completely closed, you should get a closed reading, then just as you start to open the throttle the contacts should go open. If not loosen the two screws on the top and bottom of the TPS and move the TPS until you get a close with no throttle input and open just as the throttle starts to open.

There is actually a really complex method of doing the second adjustment I mentioned using the ECU and with the engine running and all that jazz, but I've had better luck with the one I just explained. You may want to do it the hard way, but at least you can do what I said as a preliminary test.

AAC: Aux. Air Control. It's on the end of the intake manifold up against the fire wall. Controls idle charactoristics and has an idle adj. screw on the passenger side.

[niznos]

You two can probably use one of these:

http://www.zeroyon.com/techfil...4.zip

[thegary]

Thanks for the explaination niznos!..I will do some testing tomorrow.

thanksthegary

[niznos]

Your welcome, and don't forget to let us know how it turns out, that way anyone that needs this same info has something to read about when they run a search.

[thegary]

Hey....i went to test the TPS as described and i do not get any reading at all on any settings. Tried the mulitmeter on another part and its fine, so i guess this means my TPS is bad. Correct me if i am wrong..

thegary

[niznos]

thegary, your post is a little vague. Which test did it fail?

[niznos]

thegary, that service manual that was a few posts back: look in fuel and emissions chapter, pg. 11. It will explain better with diagrams and such.

[thegary]

Sorry about that....I did the tests that you posted and i also found another post stating the same thing. I went through all of them a couple of time and there was no reading. I tried some other sensor tests from the manual you posted (thank you) and everything seemed to be just fine, but for some reason i couldn't get any readings from the TPS. I might be doing something wrong, as i am new to testing electronics on cars. Parts replacing i can do, but still not quite sure if I have done things correctly with the electrical system.

thegary

[niznos]

I work on simple electronics, so I am used to the multimeter.

Wish my car would idle at 800-900. I have a problem with low idle. LOL

[thegary]

I talked to my local NISSAN dealership and one of the mechanics walked me though a couple of tests and what you described and and how i was testing was correct, and according to the mechanic my TPS needs replacing. So its only 80 cad, so i will just get one. Once i replace it, i will post a message here telling what happened. Thanks for all your help NIZNOS.

thegary

[Arrow]

I sure hope that the problem that you're having isn't the same problem that I have.... My idle is high sometimes aswell and occationally the car won't initially accelerate when I shift gears... <<<That might just be my driving though>>>

Hope this all works out for you!