I recently installed a lightened flywheel on 1999 RS as a result the idle fluctuates a good deal due to the reduced recipricating mass. I called a dealer and they told me its all managed by the computer so there is nothing I can do about it (no adjustments to make). Its not a terrible problem but if anyone has any suggestions on how to smooth out the idle let me know.

Blue

ps I wasn't sure if this is a question for the MT forum but I thought I would try here first.

Which flywheel did you install, and how light is 'lightenend'?

Did you reset the ECU after installation? If so, how long or how many miles have you driven with the new flywheel? It may take the ECU a few weeks to adjust to the modifications.

Also, I would post this in the drivetrain forum.

mrpedal,

I have installed the unorthodox racing alunminum flywheel. I believe its about 14-15lbs. Not that I think it makes a difference on this topic but I also installed the chutchmast kevlar clutch.

DreddRS25,

I did reset the ECU. At this time I have put about 130 miles over 2 days on the car since the rset. I thought the computer would adjust faster, but you think it will take a few weeks? Have you had any experience with this type of install?

Regards,
BigBlue

Honestly I am not too familiar with these types of installs.

Usually the ECU learns pretty quick. But I've read sometimes it takes a tank or two of gas to settle into a consistent MAP.

Does the idel flucuate the same when the car is cold or hot? After driving, before? And how much does it flucuate?

DreddRS25

Its been more than a two tanks now. The idle fluctuates from start to stop. It fluctuates between 500 and 900 rpm and feel like the motor will almost stall but then it will smooth out for a couple of minutes lthen fluctuate for a few and so on. I am able to drive the car fine and my left leg is already adjusting to the heavier clutch so I may just have to live with it, but if you have any suggestions I’d love to hear them.

Do you have a lightened crank pulley as well? Was reading some threads that describe the combination LW pulley+flywheel is likely to cause a rough idle and on some (mainly WRXs) missfires.

There has to be something funny with the timing. Not a problem, more like a nuisance.

Changed your plugs recently? Cleaned your airfilter? I would also take a look at the MAF to see how clean it is.

I should probably be quiet on this. I guess I'm just trying to think through it.

If the idle doesn't settle down after a couple tanks....ask your dealers service manager if they will use the subaru select monitor to raise your idle by 200-250RPM. It shouldn't hurt anything while smoothing out the idle once and for all. It is entirely possible for them to make this change....if they will decide to do it for you is another factor.

Some ECUs are more finicky than others. We're running a Fidanza (9.xlbs) with a nice smooth idle at 750RPM. We have a 98RS...but it doesn't matter....our ECU seems to be okay with it.

Jay Storm

DreddRS25,

The flywheel is the only lightened component in the drive train. Everything else is up to snuff. I changed plugs and filters about 2 months before the flywheel and clutch and everthing was fine so I don’t think that should have anything to do with it.

There was a new development today. I was sitting on the side of the road today for about 8 min with the motor idleing and the check engine light came on. So I am going to take it into the dealer and ask them to see what the error code is. I am wondering if CEL is a result of the rough idle or the other way around, or bite my tongue, maybe something else.

Storm,

When I take it in to the dealer I will ask about the subaru select monitor at the same time. Setting the idle to 800 or 850 should be fine. At any rate I thing there must be something more to this if you and others out there are able to get a 9 lb’er to work fine and I am 5 lbs heavier.

Anthony

I would bet it is a Missfire code. P113?

If you are near a Autozone, you might stop by and have them run an OBD scan. Just so you have something more to tell the service rep at the dealer.

GL! I'd like to see this through, in that I am hoping to upgrade to a lightened flywheel when I pull out my old clutch.

Misfire code… well I wouldn’t be surprised if some of the rough spots may have set off the that code. I wonder how much an OBD scanner costs? It sounds like it would be something worth investing in if the price is right.

I should have a better handle on the problem in the next couple of days. I will post anything that develops. I must say though, when the car is moving it drives great. It revs better and the engine feels like it wants to get moving. I have nothing to quantify any improvements but I can feel a difference. However, the best mod I have done so far has got to be the engine and tranny mounts. I put in the STI mounts at the same time I did the clutch and flywheel and it has greatly improved the handling and feel. The whole car feels sharp and there is no more lag in the drive line.