Both replies are right-on (though for your 88, you likely would need a test light in lieu of a paperclip). The test light works well and if you want to spend money on a reader, the LCD screen version is neat.
best bet is to send me 300 hundred dollars and I'll send ya a test light.. paper clip and instructions...
Seriously... don't waste your money...
If you search for Surging Idle Checklist... on this forum.. the first step is to check for error codes.. and there are two links there.. one has a great article giving instructions on how to check the codes with test light and paper clip.. I use tweesers.. instead of the paper clip but whatever.. It is really easy to do.. I have been checking the codes quickly over and over again... trying to get rid of some of the errors.. .
I have a 88 too.. without the check engine light.. and seriously the worst part is trying to fix the error codes.. .the easiest part is getting the error codes...
On the driver side firewall there is two plugs dangling there....
One has 4 openings at the top and two openings at the bottom.. bot only 3 wires to it.....
The other has just a single opening... and is a small grey connector
So what you do with the key off .. with a paper clip or tweezers.. is put one end in the little grey connector and the other end in (in the connecter with 4 at the top and 2 at the bottom and only three wires.. of the 4 at the top the outside is for the fuel pump.. the other is the test point...) so put the other end of the tweezer or paperclip in the 1 spot of the 4 that isn't at the end.. there is two blank spots... easy to figure out...
Now before doing anything with ignition.. with a test light hook up one end to a positive 12 v.. always on.. like battery positive and other end to the connector with 4 spots at the top and 2 at the bottom... it is the 1 wire that goes to one of the two at the bottom.. other is blank.. that the test light hooks up too...
This may seem complicated but is a joke... just print off or write this down..
Now turn the key to the on position.. don't start....
You will see the test light flicker.... but don't worry..
then you will see it start to flash...
code 13 will be flash black flash flash flash
and if there are two codes 13 16
it will go flash blank flash flash flash.. pause... flash blank flash flash flash flash flash flash....
it will repeat all the codes twice....
have a pen ready and if your by yourself and can't be in the car you may get code 67 because I tend to get it if I don't have my foot on the clutch...
Anyways so once you clear up those codes... it flashes something if everything is ok......
Next is the engine running test...
make sure to shut off the key then take out the jumper and test light wires..
If you want to clear the computer memory you can leave the jumper wire in.. and take off the test light... but you will have to drive the car again for a bit so the computer can relearn the variables...
so for the engine on test... same jumper and test light setup... but instead of not starting the car ... start it... you will see the test light flash 4 times for a 8 cylinder...
then it will do a bunch of strange reving etc. after you notice it doing different things... you will see a goose pulse (a single flash of the test light) when this happens quickly snap the throttle while in neutral to 2500 rpm.. then you will see the light flash the codes.. same as the engine off test...
Write down these codes aswell... once it finishes flashing whatever error codes twice over... then you have the option to run a different test.. can't remember what it is called.. but you have 5 minutes to tap the throttle which will put it into a different test that will not spark a cylinder one at a time and it will measure something.... then will give you a readout in multiples of 10.. and obviously something for that everything is good....
Just write all this stuff down.. and once you do these tests.. look up ford error codes.. and see whats wrong...
Only difference between this and your 300 dollar tester is the fact that you don't have to use a paper clip or tweezers and a test light.. .still have to go through the pain of finding out whats wrong!!!
Hope this helps... seriously though.. once you do it all once.. it is easy!!! any questions.. just msg me