My check engine light comes on at cruise , the primary rods go full lean but the o2 still reads rich turning the check engine light on. If you get on the throttle more the light goes off , I replaced everything in the carb ,set the float , my thoughts are leaking body or primary Jets to big ? The engine runs great but if you really pay attention you could feel a slight rpm differential when the primary rods go lean very very faint. I don't want to just switch carbs to none electronic I want to fix the problem, any ideas?

 

Did you test the float for porosity?
Stock fuel pump?

 

Replaced float along with all parts , I am assuming the new one floats, yep stock pump new.

 

Did you refer to the the factory manual for adjustment of the electronic power piston?

 

Using a dwell meter to set the reading within range? Lots of adjustments to be made in order on this carb.

 

Glad your trying to fix and adjust instead of just chunking all of the CCC. I went through this issue after rebuilding the engine and allowing a local carb rebuilder handle the electronic carb. Bad mistake, not many know how to set these electronic carbs up properly. Best to learn about it yourself and repair. First if you don’t already have one, pick up a 1981 shop manual. The proper steps are gone through thoroughly. Fix any vacuum leaks. Take note of the codes from the computer either with the paper clip method or pick up a Monitor 85 to plug in and read the codes. As mentioned the power piston needs to be set up properly, but first get the idle mixture screws set to give you the highest vacuum. Set the dwell with the power piston last.

Good luck and keep trying to troubleshoot following the shop manual. Before you know it you will have that engine purring with no codes.

 

I have all manuals I will try to make all adjustments one more time , for this car I plan on keeping it stock what ever it takes. I do not give up easy

 

I thought there was some carb gurus here that might have some knowledge on carbs , I guess they are experts on easy chit ... this is a headache

 

Did you ever check for codes?

 

There are multiple items to check. Vacuum leaks, temp sensor is it working, other electronic sensors, idle TPS sensor set correctly, idle mixture screws etc. use the specs for the 1981 E4ME Corvette. Below is a link to a YouTube video to help get things started, the specs discussed are a little different, but steps and using the 1981 corvette specs should help get you going.

 

There are a few really "amazing" and "extremely talented" Carburetor Whisperer/Guru's on this Corvette Forum and they help people with carburetor questions and issues very regularly. I am not sure your carburetor is similar enough to a normal quadrajet and the "standard" carburetors that they work on. The Computer Command Control carburetor is an interesting system that has it's own very particular needs to be managed for it to work properly. There has to be a few people here on this Corvette Forum who know your problems and how you can resolve them. Re-post this with specific mention of the CCC system and you might get a better response if they see it. There are several resources on the internet and specifically on "You Tube" that look like they could get you in the right direction.

The advice about becoming an "Expert" on the CCC was very good and the best way for you to get your Corvette to run properly. Learning the tricks for your particular fueling system is probably the best way to be able to live with such equipment in the long run. Reading and following the Factory Service Manual is probably the best way to get to know the systems. I watch and learn so much from this Corvette Forum and the great questions both asked and answered here!

I have struggled and worked/played with many different carburetors for over 55 years and I am still nowhere nearer to becoming a carburetor "expert". After learning how the L98's EFI system worked I understand the EFI technology a bit better and this led me to install a Holley Stealth Sniper EFI system on my 1968 BB.

 

Rich reading at steady state cruise, fuel being “pulled” in/ retarded timing/ too much egr/ O2 sensor in range failure/ ECM malfunction. These all assume O2 sensor is not “cooling down” during steady state cruise causing open loop. Vacuum or exhaust leak would cause lean reading. Single wire O2 sensors were notorious for degrading pretty quickly compared to today’s heated 4 wire sensors. Replaced many for skewed/ false readings. I read an old GM internal dealer memo A LONG time ago that stated O2 sensors (the old single wire type) were considered a maintenance item and should be replaced every 50,000 to maintain fuel trim accuracy.

 

Thank you 68blvert for your explanation of the above post!

I have been telling people for decades that Oxygen Sensors have a limited life and should be replaced every 50k miles. I have seen some O2's that were sitting around for many years before being used, will that affect it's life-span? Several O2's in the past years have the nifty little covers that is supposed to seal it away from air, it probably helps but they still age. This might help, when I need an O2 I just go over to the local NAPA's warehouse and get the Latest/Most recent units they have available.

The earlier C4's like mine, do not have the heated O2's like they use commonly today. On "problem" cars we would go so far as to wire-in the heater functions to keep the O2 stable and warm enough to operate continuously. Many C4's would go back into "Open Loop" while sitting in a parking lot or at a light and that is not the way they wanted the system to work. The O2 signal is very important and as they age the signals degrade, the older O2's would actually cool down faster and then back into "Open Loop". If the ECU can't get the latest data, how is it supposed maintain control of the air/fuel ratio? The early O2's sensors were of lower quality and often between the weak signal strength and the data lag, it could have serious effects on the engine and it's performance.

A New O2 is like buying a new Spark Plug, albeit an expensive one. Today with the latest technology sensors, I am not sure about the O2's NEED to be replaced every 50k. I have switched my number to 100k which is about what some of us would expect a newer O2 to start to degrade.

Supporting the notion that O2's are a "wearable part" that I personally would replace the device before it fails.

 

Thank you guys for the suggestions, as far as I can see all parts are working correctly, I drove the car with a snap on brick everything is in specs , the check engine light comes on while part throttle when the computer trys to lean out the mixture, once the primary rods get full lean the o2 still reads rich then the light comes on. I did change the o2 the new one read the same. I have to try and set up the carb to factory specs but I see there is a special tool or two I don't have. All the basics are correct timing ect , I ran a smoke machine on the intake no leaks. I would think a leak would be the opposite to what I have but tested it anyway , the code the computer throws is a rich code. #45

 

Have you tested fuel pressure?

 

Like MelWff said check fuel pressure, check float, make sure all carb screws are snug, adjust it to factory specs, make sure fuel not leaking from anywhere odd. May be as simple as trash inside carb not letting mcs push rods in to lean out.

 

negative, I changed the fuel pump with new one tho , I suppose I should check it.

 

Fuel pressure is listed as causing code 45. Recently someone else in another thread changed pumps and had 11 psi.

 

Are the carburetor jets and rods OEM? Reason to check, the carb builder I went to before redoing the carb myself installed larger jets and rods during the rebuild without taking the CCC into consideration and he thought it would get better performance. That caused a constant Rich code until I found out what they did and requested they put the OEM parts back in. After their 12 attempts I took the carb apart and reset all to factory settings to start then tuned it for maximum performance and drive ability. The important things to check are the initial settings and setup. These carbs run great after all systems are checked and tuned properly. The CCC will keep things in line afterwards without having to touch any more setttings.

I also contacted Cliffs Performance who is a guru on Rochester carbs and knows how to work on and set up these CCC carbs. He assisted me through their forum and a great resource of knowledge and parts. It would also be beneficial to provide your engine specs. I upgrade the cam, pistons, bored .30 over and tuned mine to match, replaced the heads with an older C3 set with thicker walls between valves, better springs, valves etc.. The heads from the factory for the 81 were machined thinner for weight savings but weakened them and cause the heads to crack between the valve walls, especially the middle valves due to the heat in the engine.

After Cliffs assistance I was able to set my carb up properly. They can also rebuild yours if you send it to them, if you don’t want to do the rebuild and set up or need help.

https://cliffshighperformance.com/

Good luck, keep at it.

 

thank you,
I have thought about the jet size or rods , I bought a jet assortment from Summit I haven't tried yet , by looking at the carb the rivets are still on the choke and cap still on the choke pull off almost like it's never been touched. I might give it one last try before sending out the carb, I believe the problem is with the carb.