Slightly erratic idle after new Accumulator

[Beachdrifter]

Hi all,

So I replaced my fuel accumulator with the original bosch unit (& correct size) to fix my hot start issues.

Shortly after, I noticed after the car is warmed up, the idle seemed just slightly erratic. Sometimes randomly jumping momentarily as if it were hunting, but maintaining the 700s RPM most of the time.

I'm thinking maybe I have to slightly tune the mixture screw, but not sure if lean or rich? Perhaps this will fix the idle. Any thoughts?

I remember when I replaced my WUR, I had to do considerable adjustment to the fuel/air mixture.

I don't experience any delay or hesitation while accelerating and drives great overall. This issue is just a minor annoyance I'm trying to get just right.

Thanks for any insight,

[Jonathan]

I'm thinking maybe I have to slightly tune the mixture screw, but not sure if lean or rich? Perhaps this will fix the idle. Any thoughts?

Personally, I would suggest not adjusting the mixture screw until you have exhausted all other options, adjustments, or checks.

If it is only a slightly erratic idle and just a minor annoyance, I would check for any small vacuum leaks first. Make sure connections or hose barbs are tight. Examine the tubing or hoses to see if any are cracked slightly. Engine bay connections first, as per the routing diagram, but also inspect the ones elsewhere on the car, such as those going up to the HVAC controls panel in the centre console.

If vacuum hoses are confirmed ok, check and clean grounds and electrical connections at or near Lambda system and related sensors or component. Ensure individual components are working as designed such as the vacuum solenoid valve (check the internal function as well as electrical connection).

Additional areas to ensure are working well are related to the throttle spool and linkage. It should be lubricated and freely rotating and returning to it's rest position via the spring when you release the accelerator. Confirm the idle speed microswitch is getting engaged at this rest position, both when the engine is cold as well as when it is warmed up.

[Bitsyncmaster]

Get a dwell meter to check the mixture. Never adjust the mixture to get the best idle. It will mess up what is running good otherwise.

[David T]

Get a dwell meter to check the mixture. Never adjust the mixture to get the best idle. It will mess up what is running good otherwise.


Messing with the mixture screw won't "fix" the idle. Idle quality is greatly affected by cylinder balance. Each cylinder must have close to the same pressure, spark plug gap, injector opening and closing pressures, spray pattern, valve adjustment, etc. If any of them are off, even a little, every time that cylinder comes up to fire it "unbalances" the motor causing the hunting because it makes slightly less power. Turning the mixture screw evenly affects ALL of the cylinders so you can't "fix" it that way.

[Ron]

Get a dwell meter to check the mixture. Never adjust the mixture to get the best idle. It will mess up what is running good otherwise. +1

[DeLorean03]

The unfortunate thing about these cars is when you fix something, there ALWAYS seems to be a new "weird issue", and it gets you to thinking what you did to fix the previous problem caused it. Most of the time, this is not the situation.

To keep things relatively simple, the accumulator's job is more to do when the car sits rather than active. To put it bluntly, the accumulator doesn't have much of a job when the car is running. All it does is allow fuel to flow through it as a median point between the pump and the filter.

Start at 3:16


http://www.youtube.com/watch?v=a4fJAfXYxWk

[Beachdrifter]

Thanks guys for the insight. All good pointers.

I will not mess with the mixture screw. It sounds like this is just a minor issue which I will monitor if it gets worse. I think I will just check the electrical connections and vacuum lines to see if there is anything unusual. Other than that, I will live with it. It sounds like it's your typical K-jet annoyances. Maybe getting EFI one day!

-Randy

[Ron]

You should still check the CO with a dwell meter now (and any time you change anything involving the fuel system), just for future reference...and peace of mind.