heres my situation.i got my carb done and the motor has a little shimmy to it,not much but is noticeable.the carb was adjusted according to the kit.i hooked up a dwell meter and at idle it was fixed below 10 degrees and the carb book states that this condition indicates that the feedback system is responding RICH to offset a very lean condition in the engine.one way to seperate the problem is to choke the carb with the engine at part throttle.this will increase or decrease the dwell.when i did that it increased.and it say if the dwell increases to check for a vacuum leak in the hoses,gaskets,air system etc.it also says about checking for a exhaust leak near the o2 sensor or an EGR valve that is not operating or that is leaking.now that being said all my vacuum lines are new and routed properly and everything above was checked and was fine except the egr.the egr itself doesn't leak but the vacuum line going to it has no vacuum at all whether its when i first start it up or if its warmed up.the vacuum going to the egr comes from a switch or something like that on the ps valve cover.the question i have is what is the 2 things on the valve cover and is that my problem?also everything in the carb is new mix.sol.,tps.thanks.
dwell and egr
- Thread starter RCI2990
- Start date
Welcome!
By registering with us, you'll be able to discuss, share and private message with other members of our community.
b4black
Well-Known Member
- Joined
- May 24, 2001
- Messages
- 3,773
When was the last time the oxygen sensor was replaced?
I know that this sounds silly, but check to make sure that the cap is seated right. I thought that mine was and it wasn't. Recheck the vac line going to the maps
Quoted by RCI2990
the egr itself doesn't leak but the vacuum line going to it has no vacuum at all whether its when i first start it up or if its warmed up.the vacuum going to the egr comes from a switch or something like that on the ps valve cover.the question i have is what is the 2 things on the valve cover and is that my problem?
The switch does not allow vac to the egr until it's warm or above idle. This switch can go bad and is hard to test. Block it off at the carb to see if that helps. Block off the vac to the CC if you have it.
the switch closer to the front should be the egr valve vacuum control.
Use a 1/4 vac hose with a small funnel at one end, put the funnel to your ear and use to open end around the hoses to listen for leaks. Recheck all conections.
Quoted by RCI2990
the egr itself doesn't leak but the vacuum line going to it has no vacuum at all whether its when i first start it up or if its warmed up.the vacuum going to the egr comes from a switch or something like that on the ps valve cover.the question i have is what is the 2 things on the valve cover and is that my problem?
The switch does not allow vac to the egr until it's warm or above idle. This switch can go bad and is hard to test. Block it off at the carb to see if that helps. Block off the vac to the CC if you have it.
the switch closer to the front should be the egr valve vacuum control.
Use a 1/4 vac hose with a small funnel at one end, put the funnel to your ear and use to open end around the hoses to listen for leaks. Recheck all conections.
when i checked for vacuum at the egr i did it at idle,and i forgot to rev it a little and then i noticed that there was vacuum at it.oops.i don't know if any of you guys used a dwell meter on these carbs but i just can't get the dwell to go above 10 at idle.i rechecked all of my vacuum lines and how they are routed at least 5 times.i even tried readjusting all the mixture screws on the carb to the rebuild kit.the local carb guy said he adjusted the tps to .60 volts.another question i have is i replaced the plugs about a month ago and gapped them to .060.since then i've been tinkering around with the carb to get it right and listening to the exhaust out the back it sounds like it may be missing a little bit.i'm going to pull the plugs tomorrow to check them.would the plugs fouling out cause my dwell problem?thanks.
F
Freddie's Buick
Guest
Remember a variating dwell reading between 10-50 is a good indication. It is only a problem if it is fixed after it has been warmed up for more than 15 min, ('closed loop').
Get yourself an air/fuel ratio gauge if you want to keep the ECM/CCC system.
It is a great meter to have. It indicates if the vehicle is burning in a stoichiometric condition.
Get yourself an air/fuel ratio gauge if you want to keep the ECM/CCC system.
It is a great meter to have. It indicates if the vehicle is burning in a stoichiometric condition.
Originally posted by Freddie's Buick
It is a great meter to have. It indicates if the vehicle is burning in a stoichiometric condition.
A stoichiometric condtion
I could not for the life of me spell that let alone know want it means. Please explain.
b4black
Well-Known Member
- Joined
- May 24, 2001
- Messages
- 3,773
Stoichiometry is amount of reactants to the amount of products in a chemical reaction.
A simple combustion of propane reaction:
C3H8 + O2 ---> CO2 + H2O
Is not balanced stoichiometrically until the amounts of each elements are the same before and after.
C3H8 + 5 O2 ---> 3 CO2 + 4 H2O
With gasoline, a mixture of many components, there is no simple formula like C3H8. And pure oxygen can be substituted with air (29% oxygen). The stoichiometric coefficents become 14.7 parts air to 1 part gasoline. At this ratio, all of the gasoline and all of the oxygen are being used without an excess of either. To much gasoline = rich and too much air = lean. The "stoichiometric ratio" in the fine line between being rich and lean.
There is a problem with this theory and the oxygen sensor, IMO. If the O2 sensor really sense oxygen, then what does it do during a rich condition? If a rich condition is an excess of gasoline, and there cannot be any oxygen left to measure. If there was any, it would combine (burn) with all the extra gasoline.
A simple combustion of propane reaction:
C3H8 + O2 ---> CO2 + H2O
Is not balanced stoichiometrically until the amounts of each elements are the same before and after.
C3H8 + 5 O2 ---> 3 CO2 + 4 H2O
With gasoline, a mixture of many components, there is no simple formula like C3H8. And pure oxygen can be substituted with air (29% oxygen). The stoichiometric coefficents become 14.7 parts air to 1 part gasoline. At this ratio, all of the gasoline and all of the oxygen are being used without an excess of either. To much gasoline = rich and too much air = lean. The "stoichiometric ratio" in the fine line between being rich and lean.
There is a problem with this theory and the oxygen sensor, IMO. If the O2 sensor really sense oxygen, then what does it do during a rich condition? If a rich condition is an excess of gasoline, and there cannot be any oxygen left to measure. If there was any, it would combine (burn) with all the extra gasoline.
hi freddies buick.yep its at 30 but if fluctuates back and forth so its working good.another question i have is i want to change the rear end to a posi unit with the 3.42 gears or something good.any ideas to which cars might have what i want?i have a place called harrys u pull it about a hour and a half away,but i wanted to check the local yards for one first.thanks.
