1981 Slight miss at idle, then bogging when accelerating
01-06-2018, 01:52 AM
#1
Racer
Thread Starter
1981 Slight miss at idle, then bogging when accelerating
Been running fine for a long time, then just started having this issue a few days ago.
At idle, its missing a bit. The longer it idles, the miss seems to gets worse and a bit more pronounced. Then when accelerating from the stop, the car hesitates and bogs down a bit. Then as the rpms increase, it seems to clear things out and it starts running ok again. Its like its getting too rich when its idling.
After shutting the car down today, it just didnt want to start back up. Pretty sure it was flooded. Stayed off the gas, kept cranking, and it eventually started firing over.
Troubleshooting ideas?
At idle, its missing a bit. The longer it idles, the miss seems to gets worse and a bit more pronounced. Then when accelerating from the stop, the car hesitates and bogs down a bit. Then as the rpms increase, it seems to clear things out and it starts running ok again. Its like its getting too rich when its idling.
After shutting the car down today, it just didnt want to start back up. Pretty sure it was flooded. Stayed off the gas, kept cranking, and it eventually started firing over.
Troubleshooting ideas?
01-06-2018, 09:40 AM
#2
Been running fine for a long time, then just started having this issue a few days ago.
At idle, its missing a bit. The longer it idles, the miss seems to gets worse and a bit more pronounced. Then when accelerating from the stop, the car hesitates and bogs down a bit. Then as the rpms increase, it seems to clear things out and it starts running ok again. Its like its getting too rich when its idling.
After shutting the car down today, it just didnt want to start back up. Pretty sure it was flooded. Stayed off the gas, kept cranking, and it eventually started firing over.
Troubleshooting ideas?
At idle, its missing a bit. The longer it idles, the miss seems to gets worse and a bit more pronounced. Then when accelerating from the stop, the car hesitates and bogs down a bit. Then as the rpms increase, it seems to clear things out and it starts running ok again. Its like its getting too rich when its idling.
After shutting the car down today, it just didnt want to start back up. Pretty sure it was flooded. Stayed off the gas, kept cranking, and it eventually started firing over.
Troubleshooting ideas?
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Zero1Niner (01-06-2018)
01-06-2018, 09:52 AM
#3
Dementer sole survivor
Member Since: Oct 2015
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2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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vacuum leak possibly, turn on your headlights and see if it goes away. A guy just posted a similar problem just above your post
01-06-2018, 07:39 PM
#5
Racer
Thread Starter
01-06-2018, 10:26 PM
#6
Racer
Thread Starter
headlights on didnt change anything. Quickly poked around under the hood and no obvious vacuum lines that popped off (although when is it ever something simple like that).
01-06-2018, 10:30 PM
#7
Team Owner
Member Since: Jan 2007
Location: Southern Cal Ca
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St. Jude Donor '22
81 with original carb and dist?
the running ok after warm up says computer and o2 sensor and car
warm enough, water, then the o2 leans the carb to
run condition,
choke cycle complete.
i won't type anymore until you confirm computer car.
the running ok after warm up says computer and o2 sensor and car
warm enough, water, then the o2 leans the carb to
run condition,
choke cycle complete.
i won't type anymore until you confirm computer car.
01-06-2018, 10:35 PM
#8
Racer
Thread Starter
Computer is still intact, along will all factory original equip.
The issue is there when the car is warm or cold. When at idle, its smooth for a few seconds, then slight miss, then miss seems to progressively get more pronounced. Then when I accelerate from the stop, it bogs and hesitates a bit, then smooths out. Happening at almost every stop now.
01-06-2018, 11:04 PM
#9
Team Owner
Member Since: Jan 2007
Location: Southern Cal Ca
Posts: 50,469
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St. Jude Donor '22
81 with original carb and dist, yes.
Computer is still intact, along will all factory original equip.
The issue is there when the car is warm or cold. When at idle, its smooth for a few seconds, then slight miss, then miss seems to progressively get more pronounced. Then when I accelerate from the stop, it bogs and hesitates a bit, then smooths out. Happening at almost every stop now.
Computer is still intact, along will all factory original equip.
The issue is there when the car is warm or cold. When at idle, its smooth for a few seconds, then slight miss, then miss seems to progressively get more pronounced. Then when I accelerate from the stop, it bogs and hesitates a bit, then smooths out. Happening at almost every stop now.
when it leans out and runs good, the o2 sensor is working, carb working.
I HATE THE WARM UP CHOKE BS.
some people put in a o2 sensor with a heater to warm it fast.
I forget the exact term for the o2 sensor.
Carb needs rebuilding.
easy with a couple special tools.
I made mine from different size rods.
sounds like the full rich setting is too rich, cold= full rich.
gas lately is either boiling out when i park requiring a lot of cranking
or the float is dumping gas?
My carb needs a build too.
rebuild kits are at the parts store.
takes 2 to 3 minutes for my choke cycle to finish
If I drive before it gets o2 lean, sometimes it runs crappy.
I hate that about the car.
if i let the warm up finish, you will note about 500 rpm increase and hear the car run smooth
if you had the right tool, you can adjust the
rich stop.
you will need a dwell meter set on 6 cylinder too adjust the lean stop and the air horn mixture.
carb is tricky, if you follow the service manual to build carb,
car will run sweet.
I don't know if you are new to the 81 or
let others work on it.
the symptoms you say, sound like choke cycle
is screwed up.
you can measure the total movement of the main metering rods while on the car.
so much little stuff it is hard to explain.
get a manual, the system is tricky but
becomes simple when you understand that the main metering rods, located at the top of the horn, are controlled by the computer
the total max rich and max lean can be
adjusted.
check vacuum leaks.
the hoses run to heat riser on exhaust, to carb air cleaner
to diverter to EGR to cruise control.
check the coolant sensor.
good to see a stock 81, respect the choke cycle.
the carb can be tuned like any rochester.
edit
The car will run rough when cold so rich stop probably ok.
how long have you owned the car?
they are finicky and will run rough when cold and choke is off and sometimes really sound bad.
as soon as the computer reads o2 and coolant temp
it leans out and runs smooth.
the bogging sounds like accelerator pump.
the new gas, will gunk up a carb when it is not run regularly.
Last edited by calwldlife; 01-06-2018 at 11:26 PM.
01-07-2018, 12:39 AM
#10
You live near Anaheim? We should all meet. I have quite a few 81 parts/cores.
01-07-2018, 01:07 AM
#11
Racer
Thread Starter
01-07-2018, 01:15 AM
#12
Racer
Thread Starter
ok
when it leans out and runs good, the o2 sensor is working, carb working.
I HATE THE WARM UP CHOKE BS.
some people put in a o2 sensor with a heater to warm it fast.
I forget the exact term for the o2 sensor.
Carb needs rebuilding.
easy with a couple special tools.
I made mine from different size rods.
sounds like the full rich setting is too rich, cold= full rich.
gas lately is either boiling out when i park requiring a lot of cranking
or the float is dumping gas?
My carb needs a build too.
rebuild kits are at the parts store.
takes 2 to 3 minutes for my choke cycle to finish
If I drive before it gets o2 lean, sometimes it runs crappy.
I hate that about the car.
if i let the warm up finish, you will note about 500 rpm increase and hear the car run smooth
if you had the right tool, you can adjust the
rich stop.
you will need a dwell meter set on 6 cylinder too adjust the lean stop and the air horn mixture.
carb is tricky, if you follow the service manual to build carb,
car will run sweet.
I don't know if you are new to the 81 or
let others work on it.
the symptoms you say, sound like choke cycle
is screwed up.
you can measure the total movement of the main metering rods while on the car.
so much little stuff it is hard to explain.
get a manual, the system is tricky but
becomes simple when you understand that the main metering rods, located at the top of the horn, are controlled by the computer
the total max rich and max lean can be
adjusted.
check vacuum leaks.
the hoses run to heat riser on exhaust, to carb air cleaner
to diverter to EGR to cruise control.
check the coolant sensor.
good to see a stock 81, respect the choke cycle.
the carb can be tuned like any rochester.
edit
The car will run rough when cold so rich stop probably ok.
how long have you owned the car?
they are finicky and will run rough when cold and choke is off and sometimes really sound bad.
as soon as the computer reads o2 and coolant temp
it leans out and runs smooth.
the bogging sounds like accelerator pump.
the new gas, will gunk up a carb when it is not run regularly.
when it leans out and runs good, the o2 sensor is working, carb working.
I HATE THE WARM UP CHOKE BS.
some people put in a o2 sensor with a heater to warm it fast.
I forget the exact term for the o2 sensor.
Carb needs rebuilding.
easy with a couple special tools.
I made mine from different size rods.
sounds like the full rich setting is too rich, cold= full rich.
gas lately is either boiling out when i park requiring a lot of cranking
or the float is dumping gas?
My carb needs a build too.
rebuild kits are at the parts store.
takes 2 to 3 minutes for my choke cycle to finish
If I drive before it gets o2 lean, sometimes it runs crappy.
I hate that about the car.
if i let the warm up finish, you will note about 500 rpm increase and hear the car run smooth
if you had the right tool, you can adjust the
rich stop.
you will need a dwell meter set on 6 cylinder too adjust the lean stop and the air horn mixture.
carb is tricky, if you follow the service manual to build carb,
car will run sweet.
I don't know if you are new to the 81 or
let others work on it.
the symptoms you say, sound like choke cycle
is screwed up.
you can measure the total movement of the main metering rods while on the car.
so much little stuff it is hard to explain.
get a manual, the system is tricky but
becomes simple when you understand that the main metering rods, located at the top of the horn, are controlled by the computer
the total max rich and max lean can be
adjusted.
check vacuum leaks.
the hoses run to heat riser on exhaust, to carb air cleaner
to diverter to EGR to cruise control.
check the coolant sensor.
good to see a stock 81, respect the choke cycle.
the carb can be tuned like any rochester.
edit
The car will run rough when cold so rich stop probably ok.
how long have you owned the car?
they are finicky and will run rough when cold and choke is off and sometimes really sound bad.
as soon as the computer reads o2 and coolant temp
it leans out and runs smooth.
the bogging sounds like accelerator pump.
the new gas, will gunk up a carb when it is not run regularly.
I have always felt the car runs a little rich...always can smell gas, but for the past few years, the car has run pretty good.
I have made a few changes from stock. Alum radiator, electric fan, dual stage temp fan switch, but thats about it. Everything else is pretty bone stock.
My LS1 and T56 are sitting in the garage waiting for the SRIII frame to arrive later this month, but Im sure it will be at least 6 months to a year or messing with the new frame and engine, so Ill be driving it while working on the new setup.
Last edited by Zero1Niner; 01-07-2018 at 01:16 AM.
01-07-2018, 09:46 AM
#13
GM Cert Corvette Tech
Pro Mechanic
Bird has enough parts to build an extra 81
01-07-2018, 02:12 PM
#15
The following users liked this post:
Zero1Niner (01-08-2018)
01-10-2018, 12:47 AM
#18
Racer
Thread Starter
01-10-2018, 12:58 AM
#19
Racer
Thread Starter
Actually, in case its relevant, I should expand on that last comment now that gas has been mentioned. As earlier mentioned, the wife was driving the car for a few days. She mention after coming home one night that the 'car was low on gas'. She wasnt kidding. Ive had the car for 7 or so years, never saw that low fuel light come on ever...in fact I thought it was just not functioning. Well it works. I got in the car that night and the needle was buried, and the light was solid.
Filled the tank that night, and she drove the car for the next 2 or so days. Then as soon as I got in the car again, it was driving like crap as described. Is there anything that could be result of the very low fuel level?
Filled the tank that night, and she drove the car for the next 2 or so days. Then as soon as I got in the car again, it was driving like crap as described. Is there anything that could be result of the very low fuel level?
01-10-2018, 10:01 AM
#20
Melting Slicks
Maybe just needs spark plugs or wires. Fuel pump low pressure ? Hei rotor , cap ?
Last edited by speedreed8; 01-10-2018 at 10:03 AM.