Why Idle speed can not keep up?

[quinto555]

I have trouble to keep the idle speed stable on my 323 protege 1990 SOHC 1800CC, I don't know if it's normal or not. Today I check the RPM with and without accessories as follow:

Idle speed with all accessories OFF = 1000RPM
Idle speed with headlight ON = 930 RPM
Idle speed with headlight and high fan ON = 880RPM
Idle speed with headlight, high fan and air conditioner ON = 650RPM

At 650RPM with all ON the engine is very rough, but If I increase to 750RPM when turn OFF all accessories the engine will rev. up to 1200RPM.

I think the ECU should keep the RPM stable as other car I have. Is the ECU gone bad? or maybe the speed sensor is bad? or maybe other sensor?

Please help.

[photoeye0]

With all those assessors on it is common the see the revs drop a bit, do to the added strain to the alternator.
Your revs will also drop when the A/C is on because the A/C pump adds more resistance to the crank.

I would say that it's not that big of a deal, just irritating.


And welcome to the club, BTW.

[D323]

Should pull it down more... when My AC kicks on it actually bumps the idle a bit higher.

Maybe a bad ground somewhere?

How old is the alternator? Maybe its about to go out, and cant keep up with the system. You could have it load tested at an auto parts store.

Welcome to the club!

[Speedyj]

ECU has information about running main electric accessories and it compansates idle RPM.
You have bad basic idle setting, or your idle stabilizer valve is not working properly - it could be due to bad wiring, idle valve, ecu.
Have You power steering? Are RPM rising when you turn steering wheel?

[quinto555]

Thanks, the I don't think is the altenator, the power steering has no effect on the idle speed (just tested), maybe the idle speed valve not working, but I can't indentifier the valve to remove for repare. Please help! (I attach a picture)

[Speedyj]

Thanks, the I don't think is the altenator, the power steering has no effect on the idle speed (just tested), maybe the idle speed valve not working, but I can't indentifier the valve to remove for repare. Please help! (I attach a picture)

The valve on the left is cold engine RPM riser (it closes as the engine is warming), on the right is idle valve controled by ECU.

When You switch ignition on the valve should hums.

[quinto555]

Thanks speedyj, today I have time, so will take if off to see if can be fix.

[quinto555]

I really appreciate all the help here, I'm very happy because I already fix the open circuit of the valve, now I got 12 ohms and it's working as it should be:

Idle speed with all accessories OFF = 750RPM
Idle speed with headlight ON = 750RPM
Idle speed with headlight and high fan ON = 740RPM
Idle speed with headlight, high fan and air conditioner ON = 850RPM
Idle speed when the engine is cool = 1200RPM

I spend a day for this project, but it is worth every minute.

[Speedyj]

Good work man

[Silentbob343]

I really appreciate all the help here, I'm very happy because I already fix the open circuit of the valve, now I got 12 ohms and it's working as it should be:

Idle speed with all accessories OFF = 750RPM
Idle speed with headlight ON = 750RPM
Idle speed with headlight and high fan ON = 740RPM
Idle speed with headlight, high fan and air conditioner ON = 850RPM
Idle speed when the engine is cool = 1200RPM

I spend a day for this project, but it is worth every minute.

So what exactly did you do to fix it?

[D323]

glad you got it fixed...

[quinto555]

So what exactly did you do to fix it?

The reparing is not so easy, mainly because the winding coil and the brass contact was completely fill with pressure injection black plastic, as ignoring where the wires are located I have to Dremel engrave the plastic very slowly in order not to damage the small wires. Also in order to remove the coil from the valve casting have to be first remove the return coil spring of which is epoxy clued to a small spindle, for the removar of the spring have to use mototool and micro torch and some dentis tools, then tin solder the copper wire to the brass contac, after test everything OK, I use silicone ahesive to seal if off.