Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Rebuilt Rochester E4ME on a 1981 Corvette Code 45 Running Rich on Highway

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Reaper19:
Hi everyone,

I have been trying to track down how I can stop my CEL from coming on at highway speeds producing a code 45 (running rich condition) in the ECM on my 1981 corvette. I had my motor and carb rebuilt and since I have been able to adjust the carb to idle decent, but it runs rich only at highway speeds. The motor is mostly rebuilt stock, little bigger pistons and cam, 882 heads (original 624's were cracked) but nothing outrageous and is well withing the factory specs for the ECM according to the engine builder.

Items I have completed:
- replaced O2 sensor
- replaced all vacuum lines
- checked for vacuum leaks and found none
- found the EVAP can was clogged and charcoal packed solid. I was able to break up the charcoal by shaking and re-installing. Since, the gas smell in garage has gone away. I have also ordered a replacement and will be delivered next week.
- I also found a leak in catalytic converter so I ordered a new Magnaflow high flow which will also be here next week
-I have checked carb with Dwell and got it between 25-35 at idle
- Adjusted IAB
- idle screws are both 3 1/3 turns out now

Anyone have a suggestion why I may only be getting a rich condition at highway speeds?

Thanks

Reaper19

429bbf:
there is an excellent discussion on may 08-2014 . use the search and type in E4ME look at the discussion by members (peer81 and jjr this may answer some of your questions .hth

Cliff Ruggles:
Light throttle cruise A/F is controlled by the M/C solenoid.  It may not be working correctly, or not adjusted correctly.  There are two adjustments which control this area of the carburetor, the height of the M/C solenoid, and the upper metering rod limit adjustment.

If you are certain the solenoid is working, look at adjusting it and the maximum height of the metering rods.....Cliff

Reaper19:
Thanks Cliff. I am certain the M/C is working, when I first had the carburetor rebuilt locally at a National Carb shop, it was running rich always and did not run smooth at all and I had a hard time starting when warm no matter how I adjusted the IAB or mixture screws. Afterwards I took it back and they found the newly replaced M/C was dead. They replaced it and I am able to set the dwell at idle to ~28 with the two mixture screws out 3 3/4 and IAB adjustments. I can also hear the M/C clicking away. When I take the car for a test run and then test with dwell I can see it bouncing around 54 which should mean it is calling for a lean mixture. If I slow down from highway speeds the CEL goes off and no more rich condition. I just replaced the emissions evaporator can, new Bosch O2 sensor and a Magnaflow catalytic converter. Took it for a ride without resetting the computer and still ended up with a CEL code 45 rich condition. Puzzling.

When you say adjust the solenoid are you referring to the rich and lean stops?

Thanks

Randy

Cliff Ruggles:
There are two adjustments, the actual height of the M/C solenoid, which is the first hole closest to the front of the carburetor. 

There is a second adjustment for the upper limit or height the metering rods can reach, it is below the hole right in front of the upper idle airbleed adjustment.

When we build those carburetors here, we tap those holes and install set screws, then slot the adjustment screws with a fine hacksaw blade so the tuner can make adjustments without taking the carb apart.

There could be other issues not related to adjustments, more related to the quality of the rebuild parts, float out of adjustment, wrong N/S assembly, left the spring off the M/C solenoid, worn parts, incorrect parts, "generic" calibration,  etc......Cliff

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