Check Engine light

[C3L81]

Well it was bound to happen. My perfect car has a flaw. Hopefully its a easy fix. Hopefully somone here can help me. Was letting the car run, like I do once a week when its in storage. Once it heated up to temp I noticed the check engine light came on. I revved the motor and the light went off. Exactley 3 minutes later it came back on. Ok, I shut off the car and then restarted it, Watching the clock, exactley 3 minutes later the light came back on, I repeated this 3 times before I had to go. Check the motor couldnt see anything with my basic skills. Any help will be appreciated, unless I figure it out it will see a dealer in the spring.

 

[gsimpson9981]

sounds like throttle position sensor on carb. or, o2 sensor. need to jump aldl under ashtray to read codes.

 

[22229stingray81]

Had that same problem a while back, it mostly happened when I was at idle. Took it to the mechanic and he said it needed "chasis lubrication", not sure at all what that meant, but did the trick. Need to pull codes to be sure.

-Tatortot

 

[C3L81]

Went and let it run today, same thing. Wish I had the computer to get the codes before I take it to a dealer and get screwed over. How much do they cost?

 

[22229stingray81]

You don't need a scanner, just a paperclip. I've never done it, so sit tight until someone chimes in and tells you how, but you jump 2 terminals in the connector under your ash tray. This makes it go into dagnostic mode and it will flash the check engine light in a code to tell you what's wrong.

-Tatortot

 

[C3L81]

You don't need a scanner, just a paperclip. I've never done it, so sit tight until someone chimes in and tells you how, but you jump 2 terminals in the connector under your ash tray. This makes it go into dagnostic mode and it will flash the check engine light in a code to tell you what's wrong.

Wow cool! I await patiently

 

[Yoda]

Take a look at these 2 threads, they may help

L81 Error Codes and Codes Tech Assist

GM Shop Manual (ST-364-81) and the Assembly Manual are a must have if you plan to work on your 1981, or seek valuable information in print. I have 2 of each, one in the shop with Rare and one each here along side my computer There are usually a couple for sale on Ebay at any given time.

Here are 2 links for direct access to 1981 Ebay items

1981 Corvette and 81 Corvette

Bud

 

[C3L81]

Thanks for the links. I just got back from the garage. I spent 2 hours trying to get a code. The light wouldnt blink, it just stayed on. Whats the name of the computer that gets the codes? maybee i can find one cheap on ebay.

 

[C3L81]

Got the codes, the prongs were backwards, it was the first 2 not the last. 2-3, 4-4, 5-5

 

[gsimpson9981]

Got the codes, the prongs were backwards, it was the first 2 not the last. 2-3, 4-4, 5-5

I read that to be (23) open or grounded mixture control solenoid circuit(carb); (44) is lean o2 sensor indication; and (55) is grounded +8 volt ref, faulty o2 sensor

 

[Tom Bryant]

It sounds like a dirty O2 sensor to me. You say that you run it once a week so you are going to get a lot of carbon buildup on the O2 sensor that you would not get if you were taking it for a drive on the highway once a week. I wouldn't get too worried about the check engine light until you actually get to take it for a drive and see if it comes on.

When you start your car in the driveway and let it set there and warm up it is building up a lot of carbon from the choke being on that you dont get a chance to clean out by driving it. I don't run mine near that often. When I do I try to pick a day when the roads are clean and dry and I can take it for a short drive. I judge warmed up by the oil temp. The most important thing about a warm up is to get the oil temp up to operating temp to evaporate out the coundensation and contaminants that build up in the crankcase. This is the stuff that eats away at bearing surfaces when a car sets or is run short or started to move it around and not thoroughly warmed up.

My advise is to use a Battery Tender or Battery Butler from Lectric Limited to keep your battery up to 100% all the time without overcharging. I bought 2 Battery Butlers from Lectric Limited and they have been great. They are also a lot less expensive than the Battery Tender. Then cut your warm up schedule back to once a month to limit the amount of carbon you are introducing into the exhaust system. Try to do your warm up on a day that you can take a short drive after it's warm to clean out the carbon. You don't need to run it hard, just get up to highway speed for a few miles and when the oil temp is up it's time to put it away again.

If you can't go out on the road and you have to warm it up in the driveway stay with it so you can kick it off of fast idle as soon as it's ready and get that choke open. Then hold the rpms up with your foot. Around 1000 or so is good until the thermostat opens. Now holding the brake pedal firm put it in gear (automatic) and increase the rpm up again to a good high idle. This will put a load on the driveline helping to more quickly warm the engine oil while at the same time warming the trans fluid to evaporate moisture out of it. When your oil temp guage comes up you can put the car away. You may not be able to get it as high as it would on the road but anything over 120* will evaporate out the moisture. This will also heat youur exhaust system to a higher temp than just letting it idle in the drive.

Before you get it out in the spring remove the O2 sensor and either clean it in GM Top Engine Cleaner or replace it. Many times an O2 sensor can be cleaned and it will work like new again. Then disconnect your battery for several minutes or even 1/2 hour just to be sure, to erase the bad info in your ECM. Now when you reconnect the battery and start driving the ECM will learn all new info based on your clean O2 sensor and regular driving conditions, not driveway idling. If you get any codes now they will be fresh based on actual driving and not idling conditions. Don't be suprised if you don't get any codes and the light doesn't come on.

I do the ECM erase every year before I get the car out to drive. It will make a difference on idle quality too.

Tom

 

[C3L81]

Great Advice Tom. The car was driven on the highway the week before I started it in the storage unit and the light came on. It was one of those rare 50 degree and sunny days we have been having this winter in Ohio(although I dont see many more of those coming until april=x) Funny thing is I thought the same as you, so I didnt let it run for 2 weeks, and I just got back yesterday from the car and the battery is dead! I had already planned on getting a BAattery tender type deal before I read this, but most surely I am now. Also I have been doing what you reccomended for the oil temp and Idle. Infact I pretty much do the same exact thing. In the spring I will be putting on a new O2 sensor and resetting the ecm, as you said. Thanks again =p

 

[Vader]

At least you codes should be cleared. Float-type chargers are inexpensive, and help batteries live long lives in storage.

 

[C3L81]

Went back to the unit today. Battery was all charged up and she started right up. Exhaust was very thick at start up, Putrid Rotted egg small for about 5 minutes. Had some sputtering but, Once she warmed up everything seemed normal. Check engine Light came back on again, I expected it to. Ran the codes, same ones came up. Question is was the putrid Rotten egg smell related to the O2 sensor? I read somewhere that the lucas Oil Stabalizer gets rid of it, but im a skpetic. Or is that just carbon Build up, and she needs a good highway ride? Another question, how in the hell do you change the time on the Stock radio/casette player? I read through the owners manual and nothing.

 

[Yoda]

Sounds like the choke isn't working correctly

Bud

 

[C3L81]

/sigh all this Emission control and Carb BS drives me nutts. Im no mechanic thats for sure and dont want to get ripped off. To be honest Carbs scare the crap out of me. Should I try adjusting the carb? Doesnt that mess with the ecu? I can sense a dealership service stop in the spring. =/

 

[Yoda]

The Choke is adjustable and probably stuck in one position.

With the hood open, start your car on a COLD morning, if the choke is struggling the engine will run like crap, and smoke like your attending a Golden Gate Park 40 year reunion . If this is the case, then take the top of the air cleaner off, poke the BIG butterfly valve in the front of the carb, this should set the carb to run correctly and smooth out the start up idle.

This will confirm the choke isn't helping as designed...

I've found you can adjust the choke, it is a tricky and looks rather tacky but it works On the left side of the carb (from looking from the front of the engine) with the air cleaner either off or moved to as far to the right side as possible, you will see a round device, it is mounted to the carb it is black plastic or bakolite type round looking device.

First remove the electrical wires and clean the contacts, with everything connected and the car off, find a pipe wrench (as small as possible) to fit around the plastic/bakolite. With engine cold start the engine, (be sure the wires are connected as before) if it is foundering as before, very carefully move the choke with the pipe wrench one way or the other and see if that doesn't resolve your problem.. BE VERY CAREFUL NOT TO BREAK THE CHOKE ASSEMBLY....

Your's is probably like most of ours, it still has the Stock (25 year old choke) on it, if this doesn't work and you comfirmed the choke isn't setting, your other options are:

• Replacing the inerts of the Choke.
• Replace the entire Choke with an aftermarket or NOS

Either one of these will require the poprivets to be drilled out then replaced with Fitted Screw and Nut

As you can see I am NOT ASE or certified in anyway as a mechanic, but I do know what works through years of trail and error and the gracious time of others

Bud

 

[Tritium007]

I think you pull on the seek and scan buttons to change the hour and minutes, but I'm not positive.

Cheers,
Mike

 

[Evolution1980]

Rare (or anyone else) can correct me if I'm wrong, but if his light is coming on at "exactly" three minutes, then I'm guessing that the time period from when the car's diags goes from open loop to closed loop?

As far as his choke goes, if it was sticking open, it would start up fine but then keep a high idle. If it was stuck closed, his car would barely start when cold.

I don't know how the choke works on the 81 carb since it has the computer control, but on the pre-81's, simply blipping the throttle takes the choke off. Is it not like this on the 81's and up?

Randy, both Rare ("Bud") and Tom gave ya great advice right there, especially about the need to run the car. I do almost exactly what Tom says with the car. I have a trans temp sensor as well, so I am fortunate to be able to note that as well.

I don't know if anyone has mentioned it yet or if you do it, but I make sure I use a healthy fill of "Stabil" fuel stablizer on a full tank of gas before the car goes into winter hibernaton. As fuel sits, and high octane fuel especially, it will slowly turn to varnish which mucks up your fuel system. Stabil helps slow down that change. Also, I'm assuming that you keep your gas tank full during storage. (This helps prevent water condensation in the tank.)

After I have my car warmed up to operating temperature (around 180 degrees), I'll slowly take take the RPM's up to about 3000, then bring it down. This will/should help loosen up some of that carbon. Then I'll just give it some very brief blips to 4000 RPM range just to blow out the loose stuff and move any water condesate out the back. Note: you don't want to keep the engine at high RPM's for more than 2-3 seconds, as running the engine that high without a load on it ("driveline not engaged") is not exactly good for the engine and can lead to breaking parts. But an occsional blip in Park or Neutral won't hurt it.

What I'll also do to heat the transmission up and get fluids hot, as Tom mentioned is to put the car in gear with the brake on and give it a little gas. The only difference is that I will hold it in each gear, as 1st, 2nd, and -R- have the highest pressures. And one last thing I can think of for getting the trans up to operating temp, if you can't get out on the highway, just keep your car in first gear and have fun going up and down your street a couple time while making a lot of noise. In my unprofessional opinion, with the exception of trans fluid pressure, 3500 RPM in first gear isn't any different on the engine than 3500 RPM in OD. "...as long as there is a load on the engine..."

 

[C3L81]

I don't know if anyone has mentioned it yet or if you do it, but I make sure I use a healthy fill of "Stabil" fuel stablizer on a full tank of gas before the car goes into winter hibernaton. As fuel sits, and high octane fuel especially, it will slowly turn to varnish which mucks up your fuel system. Stabil helps slow down that change. Also, I'm assuming that you keep your gas tank full during storage. (This helps prevent water condensation in the tank.)

Yes, yes and yes. I put stabalizer in it with a full tank of gas before storage.