Engine studder below 2000 RPM

[Blastedbones]

Was gonna suggest perished vacuum line.. along Warps thinking on MAP pressure, but you've checked them.

Original air ducts or triple filters? might be worth changing to triples if original ducts, incase there's a blockage or leak in the old system?

 

[warp9.9]

I'm not familiar with turning off the O2 sensor. I'd have to read up and see if or how to do it with tuneboy.

The data loader shows the MAP sensor reading and it appears the same as my friends RIII Touring (since the manual gives no readings). My O2 sensor on idle is reading .95 when the RIII Touring reads 1.975. Wondering if its the problem.

Still trying to get my fried to let me borrow his sensor to troubleshoot.

Thats one way or pull yours plug her and shut the O2 sensor down reset adaptations and take her for a spin. You could also load a map in it that has the sensor shut off to test it. if it makes a difference then you can just leave it out or change it for a wide band system.

 

[R-III-R Turbo]

you sound that way inclined - does it 'feel' like an ignition or fuelling problem?

 

[hinglby]

It acts like an old carburetor with a clogged idle jet (if that make sense). If I am gentle with the throttle from idle to over 2000rpm, there are no issues. If I'm aggressive under 2000rpm it hesitates and studders until I get over 2000rpm.

The really odd part is that nothing has been wrong for 80,000 miles. So I would think that the problem is a wear item.

My friend left town for a few weeks, so I don't have access to the RIII Touring for troubleshooting. I hate the the service manual doesn't provide readings for all the sensors, so I don't have a reference to compare the tuneboy readings.

 

[R-III-R Turbo]

And did it come on suddenly or did it develop from good to as it is now gradually?

 

[hinglby]

The symptoms cam on suddenly but intermittent. She would run fine for a week or two then the symptoms came on suddenly with the same severity every time. Now its constant.

 

[Willtill]

Run a full bottle of Seafoam through your fuel tank. See if that cures that low RPM stuttering.

 

[pjsmithres]

I read that you have check all of the wiring (O2 sensor).
Electric is good.
Gas is good.
It sounds so much like an AIR problem. Without a strong air draw, the engine would shudder.
Also, if it is stuttering, try turning it off and then restart. A few seconds off is enough.
I have had this happen and the off/on must have reset the barometer reading (air ambient pressure).
Might not be your problem but it might. After that I think there is an air pressure sensor that might be sending a bad/false signal.
There is a sensor on the intake manifold that may be dysfunctional.

Remove then and clean and replace, or replace.

I also believe in SEAFOAM flush. Great stuff for the fuel lines, start to finish.

 

[Blastedbones]

Might be an obvious question but I've not seen any post asking whether you've thoroughly cleaned the air filter?

 

[R-III-R Turbo]

The symptoms cam on suddenly but intermittent. She would run fine for a week or two then the symptoms came on suddenly with the same severity every time. Now its constant.

Sounds like fault in electronics