Ugh Carb Issues on my 81-I HATE THIS CARB! - Page 3 - Corvette Forum : DigitalCorvettes.com Corvette Forums
 
 
Go Back   Corvette Forum : DigitalCorvettes.com Corvette Forums > C3 Corvette Forums > C3 Corvette
Register Forums Garage Garage Mark Forums Read Auto EscrowInsurance Advertise

Notices

C3 Corvette
C3 Corvette General | Technical | Performance | Aftermarket | Discussions

Other sections:
Corvettes Classifieds
Corvette Detailing & Car Care
Corvette Audio/Video/Radar
General Automotive/Shop/Tools
Corvette Performance Driving/Racing

( Sponsored by: Zip Corvette Parts )

Shops/Tuners
Custom Image Corvettes
A&A Corvette
Corvette tuner

Interior
Corvette aftermarket products

Insurance



Parts & Products
Race Ramps
Edelbrock
ATI/Procharger
Corvetteguys.com
Melrose Motorsports
Parts Taxi
Airaid
Pfadt Racing
Madvette Motorsports
Hi-tech Custom Concepts
Corvette Garage
Corvette Parts and Accessories
Corvette Car Care Products
Corvette HID

Tracks/Schools
Bob Bondurant School of High Performance Driving
Corvette driving school

Wheels/Tires
Cray Wheels

Services
BADWERKS.com
Reply
 
Thread Tools
Old 06-11-2018, 11:28 PM   #31
1963SS
DC Crew
 
1963SS's Avatar
 
Posts: 4,667
Member #96709
Member since: Dec 2009
Location: Eastern, KY

My Corvette(s)
1995 C4

Thanks: 230
Thanked 873 Times in 524 Posts
Believe it or not you're getting closer. When you did the CEL code you were getting a ** ***, ** ***. correct?
That indicates a code 23. Two flashes followed by three flashes. Code 23 is mixture control solenoid either open or grounded. We already knew that.

When you jumped the pins on the ALDL plug and the MCS started clicking, that alone tested the MCS circuit and it appears to be working normally. The ECM is doing it's job and forcing the "clicking". Thanks for the new information.

Here's a pic of the ECM wiring........don't be scared.



Do you see wires #9 and #14. Use you multimeter to check the voltage on those two wires. If the O2 sensor is open it will be telling the ECM that it is very rich and it will ground the MCS to lean it out. If it keeps it grounded then it won't "click".

Start the car and let it warm up a while. Set your meter on the lowest voltage scale. You are looking for something between .2 volts and .9 volts. or 200 millivolts and 900 millivolts. This is an older and very rudimentary O2 sensor and I'm not sure if it would throw it's own code or not. if it's not running.

When you said that it ran better when you unplugged the MCS that's telling me that it was energized (wire #18 grounded by the ECM)and giving a full rich limp mode. That could be telling me that the O2 sensor isn't working. Sorry for the trouble but sometimes checking is all that we can do to find the problem.

Let the car warm up and see if it's giving any more codes other than #23. and check the millivolts on the O2 sensor wires #9 and #14. I think we're starting to get a leg up on this issue.

Last edited by 1963SS; 06-12-2018 at 10:50 AM.
1963SS is online now   Reply w/quote Quick reply to this message
If smoking marijuana causes short term memory loss

What does smoking marijuana do?
The Following User Says Thank You to 1963SS For This Useful Post:
hamerDown (06-12-2018)
Sponsored Links
Advertisement
 
Old 06-14-2018, 06:40 PM   #32
Maniacmechanic1
DC Crew
 
Posts: 5,331
Member #176497
Member since: Dec 2017

Thanks: 209
Thanked 220 Times in 200 Posts
I am going to let Gunny handle the Electronics end of your Corvette.

Something to check is the Fuel Filter.
Its located on the Q-jet inlet.
Need a 5/8" inch line wrench.
And a 7/8" or 1.00" open end wrench.
Remove the fuel filter.
Look for debris contamination.
Post a photo if you can.
Maniacmechanic1 is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to Maniacmechanic1 For This Useful Post:
hamerDown (06-14-2018)
Old 06-14-2018, 08:29 PM   #33
hamerDown
DC Crew
 
hamerDown's Avatar
 
Posts: 266
Member #132562
Member since: Oct 2013
Location: Glenolden Pa USA

My Corvette(s)
1981

Thanks: 100
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by Maniacmechanic1 View Post
I am going to let Gunny handle the Electronics end of your Corvette.

Something to check is the Fuel Filter.
Its located on the Q-jet inlet.
Need a 5/8" inch line wrench.
And a 7/8" or 1.00" open end wrench.
Remove the fuel filter.
Look for debris contamination.
Post a photo if you can.
Yes Sir, I know where the Filter is but, if dirty that should effect off Idle Engine performance too...at least I would think. And again the MCS stopped clicking, actually I don't recall the last time it did...but the Engine ran good.
Again, it just seems to be coincidence this all came about not too long after I filled the tank with 16 gallons of fuel.
If it is 'bad gas' then it should also effect cruising speeds.
hamerDown is offline   Reply w/quote Quick reply to this message
 
Old 06-14-2018, 10:15 PM   #34
Maniacmechanic1
DC Crew
 
Posts: 5,331
Member #176497
Member since: Dec 2017

Thanks: 209
Thanked 220 Times in 200 Posts
Quote:
Originally Posted by hamerDown View Post
Yes Sir, I know where the Filter is but, if dirty that should effect off Idle Engine performance too...at least I would think. And again the MCS stopped clicking, actually I don't recall the last time it did...but the Engine ran good.
Again, it just seems to be coincidence this all came about not too long after I filled the tank with 16 gallons of fuel.
If it is 'bad gas' then it should also effect cruising speeds.
Only takes a few minuted to check the fuel filter.
I never liked the E4MC Q-jet much myself.
Built for Emissions.

Stop gap before GM went to Electronic Fuel injection.
TBI & TPI.
Maniacmechanic1 is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to Maniacmechanic1 For This Useful Post:
hamerDown (06-14-2018)
Old 06-19-2018, 09:54 AM   #35
hamerDown
DC Crew
 
hamerDown's Avatar
 
Posts: 266
Member #132562
Member since: Oct 2013
Location: Glenolden Pa USA

My Corvette(s)
1981

Thanks: 100
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by Maniacmechanic1 View Post
Oh Yes Cliff uses a Q-jet carb to run 10's.
So Do I.
Pretty sure my last rebuild kit cam from Cliff...no hard parts just gaskets. (it's been a long time)
hamerDown is offline   Reply w/quote Quick reply to this message
Old 06-19-2018, 10:27 AM   #36
Maniacmechanic1
DC Crew
 
Posts: 5,331
Member #176497
Member since: Dec 2017

Thanks: 209
Thanked 220 Times in 200 Posts
Quote:
Originally Posted by hamerDown View Post
Pretty sure my last rebuild kit cam from Cliff...no hard parts just gaskets. (it's been a long time)
Cliff is Ok.
Has a website Forum just for Q-jets.
He works alot.

Pontiac Drag racer too on the street.

Be nice if you can ger that Q-jet working right.
Maniacmechanic1 is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to Maniacmechanic1 For This Useful Post:
hamerDown (06-20-2018)
Old 06-20-2018, 03:54 PM   #37
hamerDown
DC Crew
 
hamerDown's Avatar
 
Posts: 266
Member #132562
Member since: Oct 2013
Location: Glenolden Pa USA

My Corvette(s)
1981

Thanks: 100
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by Maniacmechanic1 View Post
Cliff is Ok.
Has a website Forum just for Q-jets.
He works alot.

Pontiac Drag racer too on the street.

Be nice if you can ger that Q-jet working right.
This Car is wearing me down...not looking for a Pity Party or Sympathy from anyone but, I'm 60 years old with a busted-up body from construction, my soon to be 90 year-old father is in a Nursing Home on Hospice, I'm the ONLY one dealing with his house, his bills, his meds, doing his laundry and everything about him. I run to the Nursing home sometimes twice a day, run to his house to collect bills then make sure they are correct and pay them and make sure no one broke into his house (lots of building/construction tools and materials). I also deal with my own house, bills etc-etc-etc and now this verry annoying Vette issue...and if, my Diesel Truck takes a crap I'm, screwed.
I only have a little bit of time to try to test this and that on the Vette in a 9' wide garage that I can't even open the doors all the way...I've been waiting for a fella I know to let me borrow his older Snap-On Brick Scanner and hoping he has the needed muiti-1 connector that will reach down into the ALDL. But it appears him getting back to me is not his priority....I'm mentally and physically drained.
hamerDown is offline   Reply w/quote Quick reply to this message
Old 06-20-2018, 04:34 PM   #38
Maniacmechanic1
DC Crew
 
Posts: 5,331
Member #176497
Member since: Dec 2017

Thanks: 209
Thanked 220 Times in 200 Posts
Quote:
Originally Posted by hamerDown View Post
This Car is wearing me down...not looking for a Pity Party or Sympathy from anyone but, I'm 60 years old with a busted-up body from construction, my soon to be 90 year-old father is in a Nursing Home on Hospice, I'm the ONLY one dealing with his house, his bills, his meds, doing his laundry and everything about him. I run to the Nursing home sometimes twice a day, run to his house to collect bills then make sure they are correct and pay them and make sure no one broke into his house (lots of building/construction tools and materials). I also deal with my own house, bills etc-etc-etc and now this verry annoying Vette issue...and if, my Diesel Truck takes a crap I'm, screwed.
I only have a little bit of time to try to test this and that on the Vette in a 9' wide garage that I can't even open the doors all the way...I've been waiting for a fella I know to let me borrow his older Snap-On Brick Scanner and hoping he has the needed muiti-1 connector that will reach down into the ALDL. But it appears him getting back to me is not his priority....I'm mentally and physically drained.
Holley 4 bbl
770 Cfm Street Avenger.
Electric choke.
Be my choice.
Maniacmechanic1 is offline   Reply w/quote Quick reply to this message
Old 06-20-2018, 04:56 PM   #39
Maniacmechanic1
DC Crew
 
Posts: 5,331
Member #176497
Member since: Dec 2017

Thanks: 209
Thanked 220 Times in 200 Posts
https://www.summitracing.com/parts/hly-0-80770
Maniacmechanic1 is offline   Reply w/quote Quick reply to this message
Old 06-21-2018, 07:36 PM   #40
Tom Mobley
DC Crew
 
Posts: 14
Member #114043
Member since: Sep 2010
Location: Glendale, Az

My Corvette(s)
none right now

Thanks: 0
Thanked 2 Times in 2 Posts
computer Q-jet

I think you've got a vacuum leak. I wouldn't even consider changing out the carb for a Holley. You'd have to run a carb adapter since the Holleys mentioned are square bore and will not fit on your manifold. YOu'd have to change everything on top of the engine before it's over.

Have you got a dwell meter at all or borrow one? Think of it as a duty cycle meter in this case. You need to know what the duty cycle is, that tells you what the computer is doing. To see if the MCS is working you can drop a little coffee stirrer straw in the bowl vent tube. you can see or feel it bouncing if the MCS is working.

Recall that the duty cycle is checked on the 6-cylinder on the meter.

IMO it's unlikely that something suddenly went wrong with the internals of the carb or the wiring harness to the computer.

Need to check throughly and carefully for a vacuum leak before launching off on a major repair that may not end well.

Tom
Tom Mobley is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to Tom Mobley For This Useful Post:
hamerDown (07-08-2018)
Old 06-21-2018, 07:44 PM   #41
goldata81
DC Crew
 
goldata81's Avatar
 
Posts: 8
Member #90012
Member since: Aug 2009
Location: IL

My Corvette(s)
1981 - 4 -spd

Thanks: 0
Thanked 2 Times in 2 Posts
Wish I was more knowledgeable on this subject and could help as I have an ’81 as well…. However, I just pulled the body off and have headed down the road of an LS swap. If you narrow down what may be the culprit and/or want to try swapping a part(s) on from a different vette that was running fine before the body pull, PM me and I may be able to help out in that respect.
goldata81 is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to goldata81 For This Useful Post:
hamerDown (07-08-2018)
Old 06-21-2018, 07:49 PM   #42
Tom Mobley
DC Crew
 
Posts: 14
Member #114043
Member since: Sep 2010
Location: Glendale, Az

My Corvette(s)
none right now

Thanks: 0
Thanked 2 Times in 2 Posts
goldata, do you have a known good computer Q-jet?
Tom Mobley is offline   Reply w/quote Quick reply to this message
Old 06-21-2018, 08:07 PM   #43
Maniacmechanic1
DC Crew
 
Posts: 5,331
Member #176497
Member since: Dec 2017

Thanks: 209
Thanked 220 Times in 200 Posts
I have driven 20,000 miles on the street with a Holley 770 cfm Street Avenger on my 63 Pontiac.


That E4MC Q-jet is crap next to it.


Corvette Tuned Port EFI Works Right too.
Maniacmechanic1 is offline   Reply w/quote Quick reply to this message
Old 06-21-2018, 10:05 PM   #44
goldata81
DC Crew
 
goldata81's Avatar
 
Posts: 8
Member #90012
Member since: Aug 2009
Location: IL

My Corvette(s)
1981 - 4 -spd

Thanks: 0
Thanked 2 Times in 2 Posts
In the 14 years I've owned it and 6k miles I've since put on it, I have had no problems with the carb. It now has 91K on it. The only thing I felt was a little off with it was after starting the engine cold and it running at high idle for a bit (about 5 mins maybe), it would attempt to idle down somewhat all by itself but not to low idle. Tapping the gas would let it kick all the way down to low idle like it should when warm and it would run just fine. I am not a carburetor guy so maybe that behavior is normal/expected. Paperwork that came with the car says the carb was rebuilt but there are no details on when or what was all done to it.
goldata81 is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to goldata81 For This Useful Post:
hamerDown (07-08-2018)
Old 06-21-2018, 10:24 PM   #45
Tom Mobley
DC Crew
 
Posts: 14
Member #114043
Member since: Sep 2010
Location: Glendale, Az

My Corvette(s)
none right now

Thanks: 0
Thanked 2 Times in 2 Posts
Holley 4-bbls don't work well on Q-jet manifolds, which is what he's got. He would have to run an adapter, which are often a source of vacuum leaks.Fuel line doesn't work, need a different one. most guys and up with a rubber hose, not a step forward. various lines would have to be sorted and re-attached, including the headlight doors and A/C. Air filter won't work, hits the float adjuster front and back. vacuum line to power brake booster won't work, have to replace the distributor, it won't work without the computer. carb may hit the EGR valve. new dual feed line will hit the heater hose. have to do something with the computer and wiring harness. Fix the check engine light. Fix all the vacuum lines from the canister, re-vamp the lines as the Holley doesn't have two 3/8, actually three needed. Holley doesn't have bowl vents to plumb to the canister. power brake booster, evap and PCV. Fix the throttle linkage and TV cable. This is not a simple bolt-on change-over, I've fixed a few of these, the term that comes to mind is "butchered up mess". Did I mention the hood probably won't close with Holley on an adapter? Will it ever pass smog check again?

Have you ever done this on a nice original car? OP states he bought the car new. Think he wants it chopped up? Like I said, careful and through search for vacuum leaks hasn't even been done.
Tom Mobley is offline   Reply w/quote Quick reply to this message
The Following User Says Thank You to Tom Mobley For This Useful Post:
hamerDown (07-08-2018)
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Corvette Forum : DigitalCorvettes.com Corvette Forums forums, you must first register.
Please enter your desired user name (12 CHARACTERS MAXIMUM), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
City / State / Country?
Where you live
What kind of Corvette(s) do you own?
This field is not required.
Insurance
Please select your insurance company (Optional)

Log-in


Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Powered by vBadvanced CMPS v3.2.2

All times are GMT -6. The time now is 11:50 AM.




Powered by vBulletin® Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
© 2003-2011, DigitalCorvettes.com - All Rights Reserved