I did a quick search for orielly's and they had no obd 1 scanners under $500.

Again obd ONE is expensive. Obd2 is cheap.

Its hard to fault most of the members for not wanting to shell out big bucks for something they wont use but once in a blue moon and isn't really required to work on the cars.

I have snapon, etc but the normal home user isn't going to have anything like this and are not going to be willing to pay out big bucks on it. Heck even the cheap tools are around $200 or more for obd 1 scanners.

Obd2 scanners are as cheap as $30 these days. Not having an obd2 scanner is stupid but not having an obd1 scanner is a reasonable decision all things considered.

 

How did you measure 400?

 

Ebay, TunerPro but you have to buy or make your cable, Snap On

How about an OBD1 and OBD@ scanner together?

Correct. It isn't a necessity. You just have to work much harder to do it. I suppose if your time and aggravation isn't worth anything, you can use a DVOM for pretty much anything. As to once in a blue moon, think of using it on your other carsI use my Auto X-ray on my Diesel Excursion (Very Limited data), 99 E300, 99 S320 and 91 Vette. If you want to own a car today, either bend over at your indy or dealership or figure out what you want done before you go there, assuming you need the tools.

I have 3 scanners and if there was some way I was sure they could get there and back nicely and I am not using them for the foreseeable future, I'd lend it to him. Diagnosing what is wrong with a modern car without a scanner is like sleeping with your sister. Sure, you can do both but it is going to be a painful process.

 

Did you do the whole procedure starting with the paperclip ect. and ending with the tps setting at .54
You cant just set the rpms to 400 .
Sorry just checking

 

Many C4 tachometers don't seem accurate. Surprisingly, my F-Body was. My tach we over 300 rpm higher than what my timing light and scanner said. So if you set Idle using FSM or paperclip, the engine has to be perfectly stock and no other issues which is why I said it is cheap and easy and not good.

If he had used IAC, he can tell if there is a leak if the counts are 0 and the blades are closed.

 

That's true it seems barely running is about 450 rpms I wasn't sure if the 87 had mods or not. I couldn't check my IAC but I removed it and ckleaned carefully with a toothbrush , oiled the little stem and it was rejuvenated. Good Luck

 

Hi 87 vette.

Aklim is correct here. The thing with our cars, which are an amazing deal, incredible performance even for 2015, is that the material used to make the soft goods on our cars, like rubber vac lines, gaskets, electrical lines, the electrical plugs....its all old and these rubbers dry out and cause cracks which allow extra unmetered air to come into the intake, or in the case of the electrical, they allow shorting. Combine these old components with the fact that the cars are first gen type computers, the fact is that there are usually multiple things going on with the car, many are not the actual sensors themselves. What he is saying in terms of the minimum idle adjustment, is that in the 1980's when the cars were made, and all the components were not cracked or otherwise compromised, this was a great method to do the idle adjustment. However, there is a very high probability that something "deeper" or "unmeasureable" by the ecu is faulty or comprimised.


Aklim is quite right when he says the ecu scanner is quite obtainable. Mine cost me $40 all said and done. $40 usb cable from aldl cable dot com and then tunerpro rt from tuner pro site. which is free but you should donate after you get it figured out and find it usefull. I can see, and graph, whatever is going on in my ecu. You do need a laptop as well. There is a bit of a learning curve involved but I could point you to a great thread that teaches you how to use it. it costs less than a movie to be able to scan your car forever.

The reason you would want to "see" what your ecu "sees" is that it will tell you which sensor is F'd, or, you can infer, narrow down, what is your most likely problem by "seeing" what the ecu sees.

Here is a great example that may be pertinent to your high idle situation. Lets say that you have a fairly large split, or crack, or a failed clamp on one of the vacuum hoses. These vacuum hoses are supposed to supply a sucking, vacuum source, for different components of the car. They are *not* supposed to suck extra air in. You have a sensor at the front of the car that measures the amount of air volume that is coming into the car. This measuring device "tells" the ecu how much air is coming in, and they ecu then decides how much fuel to let the injectors deliver to the car. The ecu's sole job is to keep the air to fuel ratio at 14.7 to 1, except in a few cases but mostly this is what it is trying to do, idle included. So then, if one of the 50 or so vacuum lines has a split, or a broken T, or is disconnected, or has a loose clamp, or has a faulty solenoid valve that is stuck "open", it will allow extra air from the atmosphere into that air hose, and it gets sucked into the engine intake, and gets burned! whoops! that is not supposed to happen.*only air* that is brought in past the mass air flow sensor (thereby measured by the ecu) in front of the throttle body is allowed into your engine!

So how does this lead to a higher idle? Well, the ecu has a mechanism to monitor the air and fuel ratio in the exhaust. It uses the o2 sensor to "measure" if there is too much unburned air, or too much unburned fuel (I am simplifying here but this is what is going on more or less) and based on what the o2 sensor says to the ecu, the ecu will say "hmmmm, I see that we have too much air, because i have too much unburned air in my exhaust. i don't know where it is coming from, and I don't care. but because my job is to keep the air fuel ratio at 14.7 : 1, (and right now I can back calculate that we are at like 17:1, ) and I have no way of reducing this extra air, the only thing I can do is to increase the amount of fuel, to bring that air fuel ratio back down to 14.7:1. Voila, you end up with your idle going up.

Therefore, when you have a vac leak. The car behaves just like you have pressed the throttle, opening the throttle body plates to supply more air in the intake with your foot. Even though you havn't, its coming from the leaking vac lines, or perhaps a leaking intake gasket.

Now the reason why guys on here always start with "look for vac leaks" when a "I have a high idle" thread comes up, which is twice a week for sure, is because of the fact that our cars are old, and the rubber that make up the vac hoses is more than likely cracked or comprimised in some fashion. There is a very high probability of this.

The reason Aklim says "get a scanner" is because you could "see" what your computer see's, while the problem is happening, at idle. For example, IAC valve, which stands for Idle Air control valve. It is the ecus mechnism that....yup...controls the amount of air at idle! The IAC is basically a controlled vacuum leak, meaning while your throttle body plates are totally closed (foot off the pedal) the IAC makes sure that enough air gets in to maintain an idle. It more or less acts as a small throttle body that the computer controls instead of the main throttle plates you control with your pedal. What Aklim is saying, is that if you see that the IAC valve is totally closed off, meaning, it would have a value of 0 to the ecu, which you would see if you were connected to the car with your scanner, and your foot is off the gas, and your car *still* has a high idle, then you can infer that you do have a vac leak. *EVEN* if you have combed through it, and you cannot "see" a vac leak or find one with the cigar test (btw this is how i found mine, careful around fuel, google cigar vacuum leak test) you KNOW you have either extra air coming in, or you might have a faulty IAC that is telling you its set to 0, but its actually not. There are other, more rare explanations, but its best to check this, and report back, because chances are, its this.

This is a very simplified explanation, cars are very complex systems of dynamic systems which are trying to maintain a static 14.7:1 fuel ration when everything is dynamic. I am not an expert and have just started to learn how to "read" what the scanner is letting me see.

You pretty much need to be willing to do this if you want to have your 1980's corvette run perfectly. Or, you need to pay people to do it. It becomes very expensive because C4's (like any old, rare, car) do not come around the dealership much and most tech have less experience diagnosing C4's that even me. This is magnified by the fact that they are OBD1 cars, which most new techs have no use for.


Hope this helps somewhat rather than muddy the waters!

The amount of great guys on here that are more than willing to help people who are driven to learn themselves and get things done, is mind blowing. There should really be a way to donate to like a starbucks card or something. Guys on here who donate their knowledge and time would never have to pay for another coffee ever again!

 

Minumum Idle Speed Adjustment

The Idle Stop Screw, used to regulate minimum idle speed of the engine, is adjusted at the factory,
then is covered with a plug(15) to discourage unnecessary readjustment. However, if it is necessary
to gain access to the Idle Stop Screw assembly, proceed as show in Figure C2-15.

Before checking minimum idle speed, be sure ignition timing is correct and, before making any idle
speed adjustments, be sure throttle body is clean around the throttle plates.

To Adjust :
1. Pierce the idle stop screw plug(15) with an awl, and apply leverage to remove it.

2. Adjust idle stop screw assembly(16) as required.

3. With the IAC motor connected, ground diagnostic terminal.

4. Turn "ON" ignition, do not start engine. Wait at least 30 seconds.

5. With ignition "ON", disconnect IAC electrical connector.

Important : Disconnect the distributor set-timing connector.

6. Start engine and allow to go "Closed Loop".

7. Remove ground from diagnostic terminal.

8. Adjust idle stop screw to 450 rpm in neutral.

9. Turn ignition "OFF" and reconnect connector at teh IAC motor.

10. Adjust TPS if necessary.

< With ignition "ON", use a volt meter or scan tool and adjust TPS to obtain .54 volts give or take .08 of a volt.>

11. Start engine and inspect proper idle operation.

Turn off motor and reconnect distributor set-timing connector.

 

Of course you can check the IAC if you have a scanner. You can see how many counts it is supposed to be at. Not sure I'd oil it. I don't know if the stepper motor that pulls the pintle in and out is that resistant to the fluid you put there.

 

I'd make sure the TB and it's passages are clean and the IAC housing is clean too. Something the FSM doesn't specify. As I said, the FSM ASSUMES a sterile case where only 1 problem exists. It doesn't account for leaky hoses, dirty IAC passages or faulty tach. It ASSUMES everything else works. To ASSUME makes and *** out of U and ME.

I used that stupid method and spent all kinds of time trying to figure out why it "worked" today but not tomorrow. Moron mechanic extended the IAC wires with butt connectors and one of them came loose. Had we seen that the ECM is commanding but there is no response, we'd have checked continuity from the ECM to the IAC but that procedure was there and it was the word of God Almighty so it had to be followed. It's real attribute is that there are people that cannot and/or will not adapt to the scanner technology and use it to make their lives easier and prefer to fudge around like a carbed car.

 

These are the exact procedures I followed. I even got a new IAC, before the procedure.
So I tried the smoke test and couldn't see any smoke escaping from anywhere, so.

 

Start turning the idle screw out, Rev and see IAC counts. They should go up. If it is all out of adjustment and your counts are 0, an air leak is likely. That process you follow only requires a paper clip. ASSUME much and tells little. I use a scanner for more information