91 Loyale low idle problem, EGR Solenoid questions

[Grecy]

Hi All,

 

I've got a '91 Loyale, 1.8Ltr TBI, 4x4 5 speed.

 

It's been a tropper and I love it.

All along it has idled very high on cold starts (over 2k rpm), blipping the throttle brings it down quicker than waiting.

 

After a recent long drive, it now idles extremely low (~200rpm) and it usually dies unless I pump the throttle for quite a while.

Once it's warm it runs perfectly, though it still idles low when I get to a red light.

 

I just climbed all over spraying WD40 looking for a vaccum leak.. found nothing.

 

Check engine light has been on for many years. I disconnected the positive terminal on the battery for a few minutes to clear the engine codes, and when I start the engine the light never even goes out, so the code must be getting set instantly.

 

The only engine code is 34 which my Haines book says is "EGR Solenoid (TBI) - EGR solenoid remains in the ON or OFF position during operation"

 

I'm wondering if there is an easy way for me to test the solenoid before I spend the ~$70 on a new one.

The book says apply vaccum and voltage and the solenoid should activate and allow vaccum to pass through - does that mean if I suck on it and appy voltage, I should notice it opens and allows me to suck easier? How else can I test it?

 

I imagine if it's not the solenoid, I move on to the EGR valve (which looks like ~$70 to replace with gasket)

 

Thanks very much,

-Dan

Edited January 16, 2014 by Grecy

[naru]

It is the solenoid,not the valve.

The ECU has no way of knowing whether the valve works or not,(or the solenoid either,really)

ECU can sense w/the solenoid coil is open however.

Open winding is a normal failure mode.Test it w/an ohmmeter.

 

You can fool the computer into thinking the solenoid coil is present by subsituting a resistor.

You will lose EGR function(not really desirible).

 

I have a spare solenoid I could part with.

I will PM you.

 

Your recent running problems will be unrelated to the EGR solenoid,

I would check for a corroded connection at the coolant temperature sensor and clean the idle speed control.

[Grecy]

Thanks for the reply.

 

When testing with the ohmeter, what should I expect to see if it's good vs. if it's bad?

 

I thought if the EGR was stuck open, that would cause the horribly low idle. Is that not the case?

 

What's the best way to clean the idle speed control?

In my haines it said to disconnect the electrical connector to it while the engine is idling and expect a severe change in the idle when the engine is cold if the Idle Speed Control is working well.

Disconnecting it had not noticable impact on the engine idle, and when I reconnected it I could hear a very faint humming/buzzing noise for 1-2 seconds each time I reconnected it.

Maybe I should be focusing on the idle speed control?

 

Thanks,

-Dan

[naru]

Just measured one.35 ohms

Bad one will be much higher,probably infinite.

 

Idle speed control does sound like the major problem.

Spraying intake cleaner into the passages w/engine running is the usual cleaning method.

Sometimes,I take them off to clean.Can`t remember if a new gasket would be required on your motor.

 

EGR stuck open will give you worse than a low idle.

Normally,a stuck open EGR valve will a very unsteady unsmooth idle(if it idles)

99% chance your troubles are not EGR related.

Edited January 16, 2014 by naru

[Grecy]

Thanks again, I'll test the EGR solendoid when I get home tonight.

 

I just bought a can of Sea Foam to clean the Idle speed control.. and from another post I see the FSM says the following:

 

1. Start and warm up engine until radiator fan operates
2. Hold throttle open so engine runs at 2,000 RPM
3. Disconnect bypass hose from IAC
4. Slowly pour one 16 oz can of cleaner (Sea Foam is good) into bypass air hole
5. Leave the engine to run for 5 minutes

 

I just want to check the bypass hose is the big one coming from the air intake in between the ribs into the IAC?

I assume I disconnect it on the left and spray the sea foam down the hose?

 

 

I'm also going to have a good look at the temp sensor, I bet it's very dirty (everything is)

 

Thanks!

 

-Dan

Edited January 16, 2014 by Grecy

[MilesFox]

If the egr is failed open, i can cause stalling at idle. But it is likely the EGR is just carboned up to where the port is clogged closed anyway.

 

I agree your idle issue is either a mis-read of the engine temp sensor (old or corroded) and causing the IACV to be slow to respond, or the IACV is slow to respond from carbon buildup. 

 

Allow the sea-foam to soak for a while after the engine is warmed up.

 

The IACV can be removed and access is gained by removing the alterntator for a more through cleaning.

 

Also check the PCV system and its associated hoses as they can be blocked by carbon buildup (depending on operating conditions and age/maintenance history)

[Grecy]

If the egr is failed open, i can cause stalling at idle. But it is likely the EGR is just carboned up to where the port is clogged closed anyway.

 

I agree your idle issue is either a mis-read of the engine temp sensor (old or corroded) and causing the IACV to be slow to respond, or the IACV is slow to respond from carbon buildup. 

 

Allow the sea-foam to soak for a while after the engine is warmed up.

 

The IACV can be removed and access is gained by removing the alterntator for a more through cleaning.

 

Also check the PCV system and its associated hoses as they can be blocked by carbon buildup (depending on operating conditions and age/maintenance history)

 

It has bad service history for sure.

 

When you say allowthe sea-foam to soak - what do you mean exactly? the engine will be running when I spray it in there.. so... how does it get time to soak?

 

I'm not familar with the PCV system - can you provide any more info on how I check that? I see a new PCV valve is very cheap, so I may as well just throw a new one in there...

 

Thanks, lots of great things to check

 

-Dan

[Grecy]

OK, Updates.

 

I sprayed about 1/2 a can of SeaFoam into the bypass hose into the IAC while holding the revs up.

Then took it for a spirited drive, and it felt like it had more pep at high rpms.

 

When it was hot and idling, I disconnected the IAC electrical connector and it made no difference to idle. When I plugged it back in, I could hear a faint humming/buzzing sound even louder than before I cleaned it, but idle didn't change.

 

It's still idling really low, though I'll have to wait till it's dead cold to see for sure.

 

I can't get a rresistance eading from the EGR Solenoid at all so I'm getting a new one.

 

When the engine was HOT (1/2 on guage - it gets a little hot sometimes) the resistance on the coolant temp sensor was 100 ohms. The book says it should be 700-1000.

Is that the problem?

The connector for the coolant temp sensor is clean and good, though there is corrosion around the sensor itself where it screws in.

The resistance is slowly going up as the engine cools (around 170 ohms now), but  I can't see it getting up to the 2000-3000 ohms the books says it should.

The coolant temp sensor looks expensive - can I take it out and clean off all the corosion to fix it?

I guess I can look at the junkyard too and test resistance of one.

I checked the voltage coming from the ECU to the coolant temp sensor, smack on 5v as the book says it should be.

 

Thoughts?

 

Thanks,

-Dan

Edited January 17, 2014 by Grecy

[naru]

Low idle may be entirely due to the too low resistance of the cts fooling the ECU into thinking the engine is very warm.

Might be an IAC problem too.I would repair the CTS first and see what happens.

 

Did you measure the CTS w/2 prongs?

That is the engine control one.

There is a one prong one nearby that runs the gauge only.

Common problem w/the CTS is corrosion at the connector causing too high resistance thereby making the engine think it is colder than it really is.

Not in your case,

If anything,cleaning the corrosion will lower the resistance,not increase it.

 

There is the engine section of a FSM for your car here:http://www.finleyweb.net/JonsStuff/SubaruDocumentation.aspx

1989,but,everything is the same.

CTS on page 2-7

[Grecy]

More updates.

 

Let the car sit for a few hours at ~3Deg C (close to 32F), everything feels cold to the touch.

CTS reads only 350 ohms when it should be many thousand - maybe even up near 7000 according to this:

http://www.ultimatesubaru.org/forum/topic/86260-diagnosing-a-bad-coolant-temperature-sensor/#entry725269  (and post #8)

 

At that temp, the car started but idles so low it dies.

With the CTS unplugged, it did a similar thing, but *might* have idled a little better - hard to say for sure.

 

So I'll replace the CTS and see what happens.

Anyone know what size the bolt for the CTS is? Looks like a pain to get at...

 

After that, I'll take the IAC off and clean it very well.

 

Thanks again,

-Dan

[86 Wonder Wedge]

For shits and giggles, unplug the CTS and/or MAF (do one at a time, then both, turning off the car each time of course).

 

ANY air leak past the MAF will be an unmetered air leak and can cause an idle problem. I see JY style paint markings on the air box, is that a replacement unit? Check for correct voltage output values on the MAF as well..

[Grecy]

I'll try unplugging the MAF too, thanks.

 

That pic isn't actually my engine bay, it's just one I found online.

 

-Dan

[MilesFox]

My comment with sea foam is applying the product and letting the engine stall out or shut it down so that the product can soak into everything while the engine is warm and not running, so that the product has time to do its magic before blowing it out of the tailpipe.

[jono]

on the EGR solenoid, just feed it 12V and see if it clicks - you'll feel the click of it if you hold it in your hand if it is OK, no real need to suck as well for this initial check, then maybe suck if you get clicking.

The coolant temp sensor for the ECU on its green two wire plug ? 17mm from memory with M12 1.5 pitch? thread if you were to plug it.

 

I don't know why diagnosticians don't feed sensor pickups with known range of resistanc with a ohm wheel...get a driver , you sit in passenger seat and dial up the resistance range as someone drivs, see if you get any changes. Should work for any sensor that feeds resistance values to the ECU

Edited January 17, 2014 by jono

[Grecy]

For the benifit of those searching this thread...

 

I put in a new Coolant Temp Sensor (CTS) and it fired right up and the idle was perfect how it used to be (slightly high because it's cold, and blipping the accellorator brings it down).

 

Perfect.

 

My old CTS measured a couple of hundred ohms, the new one measured a few thousand at the same temperature, and that made all the differene for correct idle.

 

For anyone with crappy/no idle, check your CTS! it only takes 2 minutes to check the resitance.

 

(I'm going to put in a new EGR solenoid in the spring to get rid of the check engine light - it's too cold outside now to mess with)

 

Thanks everyone,

-Dan