About a week and a half ago, my '81 started bogging down when I got on the accelerator. On the 14th it went in for an oil change and I asked my mechanic to take it for a drive. When I picked it up he said he thought it was either a bad fuel pump or the secondaries were not working right. Driving it home, it was doing fine and has been until today, it started up again. In terms of the fuel pump being bad, if you rev it up in park or neutral it does not act as if it's being starved for fuel. I took the air cleaner off and operated the secondaries by hand and they seemed to open and close with no problems. My neighbor (who's own truck has been doing the same thing) seems to think it is a vacuum leak. Of course, GM had to use 500 flipping vacuum lines on the car. It's drive-able, it just drives more like a 4 cylinder. Any thoughts and/or input would be nice, if you want information I may have left out, ask. I also am hoping someone could help identify the things in the following photos.

I understand one should be the coolant temp and one the oil pressure, but what's the third one?

No idea about this one, emissions?

 

I am out of town and cant get to my service manual, but I might get this a little mixed up -- neither of the first two are temp sensors. they are temperature actuated vacuum switches for the emmisions, PVC and other stuff, gotta look it up to remember exactly what.

The third picture is a solenoid controlled by the computer to enable the PVC circuit. The PVC can cause hesitation in acceleration, there are detailed procedures to check it in the service manual, but it is basically pull the valve (4 inch circular thing in the thrid picture) and see if the input is clogged with carbon.--- BUT

if you are getting serious hesitation during acceleration, I would expect it is a bad acceleration pump in the carb. With the engine off, open the throttle by hand, you should see a strong stream of fuel getting sprayed into the primaries -- if not, time for a new accelerator pump (probably carb rebuild)

since it is an 81 it is computer controlled, are you getting any "check engine" lights??? do you know how to read the codes -- if yes you should check them.

Another outside possibility is a clogged catalytic converter -- if the computer has gone open loop for a long period of time, the engine runs rich and the cat gets to hot and melts -- Check the simple stuff first.

The 81 CCC engine can be a little tricky -- but with a little understanding of how it works it can be dialed in -- stay with it.

 

oh -- and another thing. The rubber hose going into the carb is not stock -- the steel fuel line has probably been broken once upon a time and fixed with a rubber patch -- see if the fuel filter is clogged or that fuel line is kinked. should be fixed with a new steel fuel line -- a bit of a pain in the *** to fix, but sure better than a fire on the side of the road!

 

oh -- and another thing -- that carb is NOT a 1981 carb!. It does not seem to be a CCC controled carb -- if that is so -- most likely none of the computer controls are working -- the PVC solenoids are not working, and probably has nothing to do with your problem. is the distributor a stock 81 -- if so -- the computer is probably not properly controlling the advance.

Sorry -- this is all becoming complicated -- bottom line, I am not sure what combination of parts are on the car and if the computer is working or not. can you give me some more pictures -- picture of the carb, distributor overall engine compartment -- do you know if the computer is still working or has it been removed/disabled?

 

The carburetor shoots gas into it fine. I had thought of the converter before and it is something I'd wanted to straight pipe anyways. The engine light has been on since I first met the car some years ago. The carburetor on it is not computer controlled, most of the smog stuff is gone and I have a new vacuum ported distributor in my basement waiting to be put on the car. Can all of those things be plugged off then? I want to ditch the computer system entirely.

 

I did pull the fuel line and checked the filter, no clog, and I am the one who broke the steel line

 

All you need to do to get rid of the CCC is change the carb and distributor with a vacuum controlled distributor (Another 1981 ccc corvette bites the dust) -- take the light bulb out of the check engine light.

bogging down under acceleration is normally accelerator pump or vacuum advance ( it doesnt sound like you have any). Check for vaccum leaks by spraying ether (starting fluid) around the base of the carb -- if the rpm increase you have a leak -- the vacuum lines are not as complicated as it seems, but vacuum leaks are normally the cause for bad idle. is it idling ok? if yes -- keep checking for fuel (fuel pump, fuel lines, fuel filter, carb)

 

there are a few rubber lines I'll replace after work tomorrow *crosses fingers*

 

The second picture is the EGR solenoid. The first picture shows the two vacuum switches controlling the evap canister, I don't recall what the other controls, and the hose that's off should go the the bottom of the air cleaner, but none of this is your problem. Since someone swapped carbs, I'd start there. If it were a vacuum leak, you'd have idle issues, since you didn't mention that, I'd guess it's not vacuum. The secondaries on a Q-jet have two main parts. The air valve (on the top of the carb that you can push with your finger) and the butterfly's in the base plate that works with the linkage from the primary side and the throttle cable. There are usually two lockouts for the secondaries. One is from a vacuum pot (depending on the year) and the other is mechanical operated through the choke linkage. I'd guess this is where your problem is. If you can post pics of the choke side, it might be helpful in seeing how your carb is set up.

 

Can the vacuum lines to the EGR solenoid just be plugged off? The car does have idling issues, I didn't mention it because I didn't think of it; it has idling issues since I bought the car. I have an Edelbrock carburetor, but it needs to be rebuilt and when its ready to go on the car, I also have a new vacuum ported distributor for the car. My goal is to dump the computer and emissions (mainly vacuum lines).

 

a can of Sea Form did a great improvement to my 81.

 

The picture of the carberator shows that the EGR valve has already been removed. That diamond shaped silver plate is a cover over where the valve used to be. Strange since the earlier pic of the solenoid clearly shows the valve in place (3 inch diameter flying saucer shaped dingy). if the valve is gone, the solenoide is doing nothing -- and will not effect the performance of the car -- take it off if you want.

If the car is not idling and not accelerating -- I would put the new carb and distributor on and begin tuning it in from there.

 

oh, and another thing (I really should take a closer look at the pics before I submit a reply)

There is no choke on the carb! -- that carb is VERY suspect. I really think you should put a new or well done rebuild on the car before you waste any more time trying to get the car running with such a suspect carb on it.

good luck

 

Oh and another thing.

If you take the red solenoid off the car I will buy it from you!!!!!! No kidding -- I want the whole assembly (there is a white plastic solenoid just under the red one -- I want the whole assembly) I am trying to bring my 81 back to pure stock and mine has broken.

 

A couple of weeks back I bought the EGR block plate and put it on. Within a week the car first began acting up so I put the EGR valve back on in hopes that may have been the culprit. It was not so today I put it back on. Since I want to dump the emissions crap, I have no problem removing the solenoid, but I probably won't be able to get to it till sometime next week.

 

I don't have my 81 shop manual in the house, but I think the second one controls the vacuum operated heat riser, attached to the right side exhaust manifold.

 

Do you have any PICS of the the hoses coming off the AIR pump?
I have one that is hanging and cant fig out where it plugs in. Its a longer hose coming off the top.
I looked at my diagram on the hood but thats like trying to read Chinese.

 

Does the engine run OK until it heats up? If so it might be the HEI module. The modules fail in limp home mode as they don't have enough energy to ignite the mixture under accelleration.

 

It does so-so when cold. MY neighbor's truck was acting the same way as my car and after six weeks and several other repairs, he traced it to his coil. It was getting really hot, he couldn't hold it for more than a few seconds. Right now I'm hunting for vacuum leaks since that would be the easiest and cheapest. As I've said, I have an Edelbrock carburetor, a new vacuum ported distributor/coil/cap and it looks like I'm buying a used Weiand manifold. When the Edelbrock is finished being rebuilt my neighbor and I will start on all three projects. Hopefully that does solve my problems and I'll finally have a Corvette that drives and acts like a real Corvette.

 

I'd start by getting the carb (or another one) complete, tuned and on the car. I can see there's no secondary lock out, and I highly doubt there's a fast idle cam on the carb. I'd start with the carb, we already know it's got issues...