Idle Speed Keeps Changing?

[Vincent Hill]

I did a search but could not find what I was looking for. I lowered my Idle and it was fairly steady between 850 low and 1050 High with normal about 950. Nothing to complain about. Then my wife put in some Sunoco and now it is all over the place from 600 to 1350. I KNOW Chevron is the best to use and NEVER Use Shell, but I plan to take a short trip and will have to buy gas that may not be Chevron!

I just replaced / Installed the restrictor BETWEEN Oil tank and the AirBox! What else do I need to check?

[scottb]

Bad mixture sometimes causes fluctuating idle.

[Vincent Hill]

Originally Posted by scottb

Bad mixture sometimes causes fluctuating idle.

You are speaking if the Fuel Adjustment screw? I know that Air Temp seems to have a lot to do with where it idles, Maybe I will note where it is set and turn it a little both ways (Starting with Richer) and see if that seems to help. I know that most of the fuel around here now has 10% Ethanol and I know that does not help anything except to lower the fuel mileage.

[Vincent Hill]

I know that Vacuum leaks are connected to Strange Idle problems and last night when I was resetting the Idle, I disconnected the back vacuum line to the Distributor and it has no vacuum and changed nothing. I am not sure this line has any vacuum while at Idle. But the front vacuum line also had no vacuum when I disconnected it! I am 99% sure that It should have some Vacuum!! So this weekend I will pull a few things off anc see if it is connected and see if the line or the source has a problem!

[GothingNC]

I am chasing the same thing with my 82 SC

Idle when warmed up is a rock solid 950 then once in a while it will start hunting from 800 to 950 for a few minutes then it is back to normal

If I shut off the car for few seconds when the idle is changin and restart it is then back to normal

Completed a tune-up over the weekend with valve adjust and the results are the same.

I'm going to try to lean out the mixture a hair since it usually occurs when it is warm out

Try to stay away from Ethanol, last year I tanked up at a station that had it and I had hot start problems for a week.

Gas station by my house has a sign on the pumps "100% gas, no ethanol added"

[Vincent Hill]

Originally Posted by GothingNC

I am chasing the same thing with my 82 SC

Idle when warmed up is a rock solid 950 then once in a while it will start hunting from 800 to 950 for a few minutes then it is back to normal

If I shut off the car for few seconds when the idle is changing and restart it is then back to normal

Completed a tune-up over the weekend with valve adjust and the results are the same.

I'm going to try to lean out the mixture a hair since it usually occurs when it is warm out

Try to stay away from Ethanol, last year I tanked up at a station that had it and I had hot start problems for a week.

Gas station by my house has a sign on the pumps "100% gas, no ethanol added"

Thank You, "IF" we were where you were on this I would be happy! ours is between 800 to 1100 and I slowed it down a little so now it is between 750 to 1,000 RPMS. My thinking is you can always Raise the Idle with your foot, but you cannot lower it! I know it is hard on the Crank Bearing to run too slow but it is hard on the pocket book at the Gas Pump the other way.

Also we has about a 50 RPM window with Chevron and now a 250 window with Sunoco. I am putting in the Tie Rods this weekend and plan to check the Vacuum lines and distributor and the adjustment on the Dyna Tune module. If I can make ANY Difference I will post what I did!

[Vincent Hill]

Originally Posted by scottb

Bad mixture sometimes causes fluctuating idle.

Bingo!

I got out the 3 mm wrench and resolved everything! It was rich! Thanks

[scottb]

Originally Posted by Vincent Hill

Bingo!

I got out the 3 mm wrench and resolved everything! It was rich! Thanks

I'm glad it worked out!

[GothingNC]

Glad it worked

Just got back into town and plan on leaning the mixture and hope it helps.

[Vincent Hill]

Originally Posted by GothingNC

Glad it worked

Just got back into town and plan on leaning the mixture and hope it helps.

Once you do, watch the Oil Temp and if it is more than about 1/8" above the center line think about richen it back a tiny bit!

[stlrj]

Originally Posted by Vincent Hill

Bingo!

I got out the 3 mm wrench and resolved everything! It was rich! Thanks

I know that CIS does not drift into rich by itself, but has someone been tampering with it?

[Vincent Hill]

Originally Posted by stlrj

I know that CIS does not drift into rich by itself, but has someone been tampering with it?

No, (And do not think this did not cross my Mind! My thinking is the car is NOW being driven about 10 times more than it was and fairly seriously. My thinking is that maybe the accumulator or Filter got cleaned out and that changed how it ran. PLUS, it is now summertime and it was set when it was Cold. Also the injectors may have been dirty and not spraying 100% and now that they are they are spraying a lot more hence the rich condition.

I plan to drive it over 1,000 miles this weekend and if nothing changes then I WIll KNOW if it is set for good or more changes are needed?

[GothingNC]

Vincent,

I got ahold of a 3mm allen tool and leaned it out about 1/16th of a turn, maybe less.

I was not sure if I had the tool all the way into the mixture screw, felt too easy to turn with very slight resistance.

This morning the idle stayed steady after the motor warmed up and did not change at all during the commute to work.

I'll see what happens on the way home when it's warmer out.

[Joe Bob]

Make sure you put it on an exhaust analyzer.....too lean is a bad thing.

[Vincent Hill]

Originally Posted by mikez

Make sure you put it on an exhaust analyzer.....too lean is a bad thing.

Amen on being too lean, BUT saying that, it was the Exhaust Analyzer that got the car too rich to begin with!

It should not turn real easy! If it does, then it can go out of adjustment. Take the airfilter off and look at the screw while turning it! If it is turning, then spray it with Brake cleaner and screw it out a few turns and put a few drops (And I mean 1 or 2 Drops) of BLUE Loctite and screw it back in that should keep it in place!

[dicklague]

Make sure you have a good AFR. For a little over $400 you can install one our host sells that includes the wideband sensor and data logging. Install it permanently and you constantly know what is going on.

[Vincent Hill]

Originally Posted by dicklague

Make sure you have a good AFR. For a little over $400 you can install one our host sells that includes the wideband sensor and data logging. Install it permanently and you constantly know what is going on.

I have an Innovate Data Logger on my 2000 Kawasaki ZX12R that I use for Land SPeed Racing. For that I NEED to know when spraying between a 150 to 200 shot of NOS but for this car it would drive me crazy because I would want exactly what I wanted and be tuning it every day!

I have a new Wrinkle on this problem! After a 1,000 mile round trip betwen Washington, DC and places in Ohio (Got 24.5 MPG going and 25.5 MPG Returning driving between 70 and 90 MPH with a few burst up to about 130 MPH.)

When I got home, On Monday I changed the Oil and Filter and put in a set of NGK Iridium plugs and cleaned up a few other things. NOW I cannot get the Idle "LOW Enough" About 1100 to 1300 RPMS. I have the bypass screw all of the way in and turned the fuel screw so it ran clean (As rich as I could make it and it still run good). Tonight I plan to Retard the timing a little to LOWER the Idle because I am out of ways to lower it Dumb Car just wants to run too well

[dicklague]

LSR!!! cool. I know a bit about it. Ever seen WORLD'S FASTEST MOTORCYCLE DVD? BUB event 2006.

[GothingNC]

Voncent,

Hope you get your high idle corrected, maybe you bumped something loose causing a vacuum leak or the throttle linkage is sticky when hot.

One my way home toady I reached the usual spot whete my idle would start hunting and this time it was almost smooth. If I revved the motor it would drop to aabout 600 RPM and then raise back up to 950 once and then stabilize. Still smells a bit rich but not as bad as before.

[Vincent Hill]

Dick, Yes I saw that and as fast as I want to go, it is not that fast!


John D, you now have touched on something I also check but never mention it! "Smell". If you can smell it, it is still rich! I have a statement on doing the adjustment with an "L" Shaped Allen. With the "L" Facing you, Left is lean and Right is Rich! There is about 15 to 20% of a turn you can make with that wrench between the Fuel lines and the Rubber cover. Move it more to the left and watch the RPMS rise. Make the adjustment to the Idle screw after and see if you can still smell the fuel in the exhaust?

Last night I turned the timing down a ver small amount and "Finally" was able to use the Bypass Screw to raise the Idle a little. Started it up today and it seems to be OK