Revs drop too fast when the clutch pedal is pressed down

[mikamk]

Hi guys.

My 1992 4G63 N/T Eclipse (European model) is a bit ill. The car works pretty nicely, with the exception of this problem. When driving, and pressing the clutch pedal down with the car in gear, revs drop rather too fast towards idle. They go down to idle (about 900RPM or something like that), not lower than that. The car feels like its bogging down then that happens.

There are no problems whatsoever when the car is idling and the clutch pedal is pressed down. The car doesn't die or anything.

The difference in the speed the revs drop between just coasting and having the clutch down is quite large.

This problem leads to shifting being a bit difficult.

I couldn't really find anything about this on the forum by searching. Any ideas what I should start looking at? The car is my daily driver so I can't just dismantle the whole thing and try to figure out what's wrong.

Oh, and by the way, even though the car is marked everywhere as a 92 model, it still does have the popup headlights for some reason, so it might actually be really a 91.

 

[DSM90AWD]

Unless I'm missing something this is normal.

With the clutch pedal engaged your engine should return to Idle speed (as set by the ECU) rather quickly (much quicker than with the clutch out) since your engine is no longer linked to the drivetrain's inertia/vehicle speed.

The rate of engine speed loss with clutch engaged is solely dependant on the intertia of the rotating assembly (pistons, rods, crank, flywheel, clutch). Lightening any one (or more) of these would cause your increase the rate of decrease of your engine's speed.

 

[mikamk]

Unless I'm missing something this is normal.

With the clutch pedal engaged your engine should return to Idle speed (as set by the ECU) rather quickly (much quicker than with the clutch out) since your engine is no longer linked to the drivetrain's inertia/vehicle speed.

I have to admit that I never really paid attention to how fast the revs actually drop on other cars with clutch on/off, but it certainly isn't as fast as they do on my DSM. I mean, for example, I have to shift really quickly because otherwise my RPMs will have fallen too much from the clutch pedal being engaged. It makes, for example, double clutching a real pain.

The 'problem' just bothers me a bit that I've never seen it before. I can live with it in case it is nothing serious.

Of course I have no idea if somebody has actually modified the engine internals as I have no clue who owned the car before the old lady who owned it before me. Sounds rather unlikely.

 

[Shifty]

Know of any tranny work that has been done?

I know a lightenend flywheel would cause this.

 

[Generation1JeY]

ya i was about to ask u if u had a lightened flywheel, this will really effect the roatation of ur motor, when ur not giving it gas it will slow down a lot faster

 

[LucasEnglish]

A stock DSM on a free rev or when the clutch is pushed in should drop to around 1200rpm and than slowly dorp to 800rpm or so. If it does not to this there could be a few problems. The ICS is bad or the cips in the ECU that run the ICS have fried. This is ware I would start checking.

 

[mikamk]

I don't know of any tranny work like this being done to the car. The car was bone stock as far as I know when i purchased it around a bit over a month ago.

Thanks for the ideas guys. I'll look a bit into the flywheel business.