1993 pick up 5 spd, 22re, 140xxx miles. Ok so I've had this damn looping idle for about 2 months now and have finally broke down and decided to take it in to the stealership to get fixed. But today after school I decided to try the self check the from 4crawler.com. So i put in the paperclip and like magic the idle levels off and sounds like the good ol days. My question is, can I run with the paper clip in? Will it hurt my engine? Any help much appreciated.

 

I don't know if you can, but I wouldn't. Your gas mileage would go to hell, if nothing else.

You need to check your timing. What's happening is in check mode, paper clip in, the computer retards the timing. Or rather, it doesn't advance the timing. Allowing you to set the base timing. When you remove the paper clip it lets the computer take advantage of it's ability to advance the timing based on sensor readings and certain engine conditions. For example the knock sensor and engine rpm.

So, my theory is your timing is too far advanced. Because when the computer is in control of advancement it can't find a low enough setting. And this is causing your idle to vary some except when you put the computer in check mode. Which it shouldn't if set correctly. The timing should advance by 5-9 degrees when you remove the clip, from 5 deg BTDC to between 10-14 deg BTDC, according to the FSM. But the idle should be unchanged with the paper clip in, staying around 750 rpm +/- 50 rpm.

 

Your "loopy" idle is most likely caused by your idle RPM's set too high. If the idle is set above 950 RPM's, the computer will go into "fuel declaration cut" mode, and that's when the varying idle begins. Shorting out TE1 not only causes the timing to decrease, but it also causes your idle to decrease as well. When this happened, the RPM?s went below the 950 RPM threshold and solved your varying idle issue.

Do not drive around with the terminals shorted. Shorting out the terminals will cause the timing to be infinitely set at 5BTDC permanently. Hell, the truck probably wouldn't even be drivable anyway.

 

Alright thanks for the help guys. I guess I was just looking for an easy way out. I just cleaned my throttle body hoping that it would help, but nothing. I have my idle screw all the way in so I can't lower it anymore. The truck idles great for about the first 5 minutes, then it goes to crap. I read in the fsm that a low coolant level can cause this because of air pockets. I checked and my coolant level and it was low, so I guess I'll add some more tomorrow. I've found a brand new Toyota TPS on ebay for under $200 that I think I'll try next?

 

Test your old TPS first, it may be o.k. still.

I take it you don't have a timing light? If it isn't set correctly it might cause your idle to be too high to be properly adjustable with the idle adjustment screw.

If the timing doesn't need fixed, then your throttle stop screw probably needs backed off a touch. But that's the last resort, it shouldn't need adjusted unless someone has moved it since the factory. Which does happen, mine had been moved when I bought my truck.

 

Before you throw money at a new TPS do like the guys above are suggesting and check your timing. I had the same issue as you after rebuilding my head last winter. I had my timing too high so I wasn't able to turn the idle screw enough to get the idle low enough. Once I set my timing correctly I was able to get the idle right.

Rob