I am stumped

on my 87 lx i had long tube header's and i extended the o2 wires my self they came out all the time they caught everthing some times i rode for a day or so without o2 sensors never had jumping idle. i had that on my gt when i first bought it put in some fuel injector cleaner/gas treatment and some stp throttle body cleaner and rarely does it every do it anymore. (use to go from 1k to 500) if that doesnt work for you try to replace your plugs wires and coil. is it mass air?

could be a nice set of wires wont hurt. how many miles on the car? dirty injectors and throttle body can cause bad fuel milage,loss of power,and hesitation.(do you have a aftermarket ignition?) ooh and bad idle i would start there and re-place the o2 sensors too. all these things have to be re-placed around 100,000 or so. this is what i would try first before i dig deeper (you would be surprised how much hp shot igniton wires,dirty injectors/throttle body and bad o2 sensors would cost you just my .02

Probably wouldn't hurt to replace the fuel filter while you're doing the other maintenance stuff. You'd be surprised how often those things cause trouble.

Cheap and easy things to do...

1.) Remove the MAF element and spray it with electric contact cleaner or non flammable brake parts cleaner (same thing , just a bigger can and cheaper too).

2. Check the TPS voltage - should be .90-.97. Use a Digital voltmeter to measure the voltage. If the TPS has more than 150K miles on it, replace it.

Here’s a TPS tip I got from another stangnetter…

When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks. Set it at .97v-.99v, the closer to .99v the better.

(copied from MustangMax, Glendale AZ)

1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

3. Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

4. Check the procedure for your year, on my 90 I have to turn the idle screw until it just touches the tab, then insert a .010 feeler gauge and give it about one more turn. Then you adjust the TPS voltage to .98v, reset the computer. Start it up, if the idle is to low then turn the screw in until it is just right, then readjust the TPS voltage to .98v and reset the computer and start it up. The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.


NoGo50
Super Stanger

91 (R, M) System running lean - Fuel control
41 (R) System lean - Fuel control
(M) System was lean for 15 seconds or more (no HO2S switching) - Fuel control

Looks like you are starving for fuel check your fuel press and see if its low maybe you fuel press reg has gone bad.