Duratec - surging at idle

[Elv15]

Any other duratec owners have idle problems when the weather warms up? My car runs fine when it is cold. And runs fine when warm on the highway, but in traffic, it will not idle very well. The tacho hunts between 1000rpm (which is where it usually idles) and 500/600rpm. vrooom. vroom. vroom. :?

I'm suspecting the air temp sender...

Thanks,

Tom

[Elv15]

:arrow: No body else has this issue...hmmm :?

[JohnCh]

I haven't had this problem, but now that I have publicly made that statement, I'm sure it will crop up this weekend :wink:

-John

[slomove]

Well, I have this issue with my Mitsubishi Galant (AFAIK some intake leak). But this piece of junk is already 11 years old and I don't care anymore.
Are ECU/Injection stock? Which sensors are hooked up? Is it a new symptom or had this all the time?
If you have an aftermarket ECU you could check the idle control settings, play with the maps etc (sorry to mention the obvious...).

You could also try to measure the signal voltage of the sensors you got. If you disable the ones that show a synchronous fluctuation you may get a hint.

Make sure that you don't have a nervous right foot :wink:

Gert

[moosetestbestanden]

My idle has always been variable and temperature doesn't seem to matter. Worse, the variable-ness is variable. That is, it doesn't always occur, just most of the time.

I was kind of hoping you'd know, Tom... I have yet to have a look at things w/ the Easymap software as my notebook died right about the same time as I got the car. I think I'll have to see if Fearless Leader (such as we have at the CCC), namely Magnus, will have a look at things w/ me one of these days.

[magnusfeuer]

After spending several hours on the driveway playing with my idle settings, here are my $.02 on idle surging.

A map usually has increased fueling at zero throttle position (or the lowest manifold air pressure) just under normal idle (500 RPM). The thinking behind this is that the engine will be "picked up" by the increased fuel if it is about to stall. This pickup can be augumented by letting the idle bypass valve add a bit of air in the same map area. The ignition can also be advanced here for an even greater effect.

What has generated surges for me is that as I let go of the throttle, the engine falls into the pickup area, where it gets too much fuel (and possibly air), in effect giving it the equivalent of a light blip.

This blip can be worsened if you run of manifold air pressure as the increased pressure generated by the blip will move the engine into a part of the map where even more fuel is added.

After the blip has done its thing, the engine falls back into the pickup area, where the process is repeated until you send in a post on this site.

The reason that you do not get surges in cold weather is that the higher oxygen level in the (denser) air can alleviate a rich condition in the idle part of your map, thus hindering the engine from falling into the pickup area in the first place.

To fix. Lower the 500 RPM pickup area fueling (and possible your idle fueling as well as it may be running rich) and play around with it until you have no more surges. Make sure that you can give the throttle a good blip (to like 3000 RPM) without stalling the engine as it falls back down.

When I did the idle setting on my car, I had little use for the lambda reading since it was all about the feel of the idle. I think I run slightly rich on idle right now, but it is rock solid unless I go up too high in altitude where my lack of barometric pressure compensation gives me idle surges (less dense air). I've just been to lazy to fix this.

/Magnus F.

[magnusfeuer]

Oh I forgot.

I am more than happy to have a look at the idle of any seven as long as their owners haul car, software and the necessary laptop cables to my house in Newport beach.

My antibiotics induces dizzyness will only add to the quality of my work.

/Magnus F.

[Elv15]

surging

All, I spent some time yesterday with the car in the driveway. I did a bit of logging with the easimap software and the one thing that stands out is the ignition advance is bouncing up and down. This could be a side effect, if Magnus's theory is right...

If anyone want's to see my map or logs I'm happy to share! :D

I'm going to spend some more time with it today and I'll report back what I find.

Tom

[moosetestbestanden]

Tom, you've got a 2.0L, is that correct?

[Elv15]

Yes, it's a 2.0L.

After looking at the logs, it seems like the ignition is bouncing because it's trying to correct for the engine slowing down. This causes the motor to speed up, whereupon it trims the advance back. bounce bounce bounce. Arrgh.

I'm still trying to learn how to use the software and learn how each map relates to the others.