ERG Valve stalling after a few seconds (Fixed)

[chrisP]

In case it helps anyone else, for a long time I have has a cold start stalling problem - the engine runs for a few seconds and then dies unless you blip the throttle.
After going through the manual.
1. Fitting a new IAC valve, which didn't make a difference, but meant I had to take the inlet manifold off to get to a sheared bolt
2. Cleaning all the gunk out of the ERG valve and the manifold - both were pretty blocked
3. Testing the ERG valve by putting a tube on it and sucking....... it moved fine and sealed pretty well

I was still having a problem

So I decided to disconnect the vacuum pipe from the valve and seal it with a bolt, while I started the car, it didn't stall....
I expected once I reconnected it, it would stall on the next cold start, but it hasn't has started every single time.

Maybe there was some kind of air lock in the electrical actuator.... just thought I would share.
Chris

[Chas54]

Chris
Ive just changed my EGR valve because it was passing slightly , but enough to ruin the vacuum at idle . The actual valve head is damaged , i can see as ive released the diaphragm . Anyway ive replaced the valve and thought the problem fixed , the vacuum is now good ------ or so i thought until this third start (hot engine) since changing it and the vacuum is at 50mbar . I thought the valve must be passing again and tried your method of pulling off the hose from the solenoid to the actuator and the vacuum immediatley inproved to 36mbar. There has to be something wrong with the little solenoid switch as at idle there should be no vacuum applied to the actuator . I am now convinced that my period of running in the past, with this valve partly held open , has damaged the head and seat of the EGR valve.

Ive just got to figure out why the solenoid is holding a vacuum on the actuator . I cant risk damaging my new EGR.

Anyway thanks for highlighting this

[tigerdog]

Interesting thread. I've been having a bit of a challenge with emissions due to NOx levels, which EGR treats. It's as if my valve isn't opening at the right time or as much as it should. I never thought to check the solenoid/actuator.

[Chas54]

I have just taken my solenoid off as it is holding the EGR open by trapping the vacuum in the actuator line after the solenoid closes.
I have not found the vemt on it yet .
When the solenoid closes it should vent the actuator side of the vacuum line to atmosphere otherwise the trapped vacuum will hold the actuator open .

The secondary throttle solenoid does just that and is described in the manual .

In the manual EMK3 diagnotic chart -EGR
There is a box suggesting the vent filter may be blocked------ Does anyone know where on the solenoid valve this is ?? I may have to put an airline on it and pump up the pressure on the actuator side of the solenoid to see if i can see any venting ???

Any advice on where i should look welcomed

Charlie

[tigerdog]

I believe the filter is the little round black thingie that press-fits onto the blue base. You might try removing this and see if the behavior changes.

[Chas54]

Thanks , you're right , it's the little black plastic thing on the upper part of the solenoid .
I have had mine off the car and could tell the upper spout of the vacuum part that goes to the EGR actuator was not venting to atmosphere when de-energised . I found a picture of a similar device on the internet and the vent is through the hollow spindle into the black filter.
Checking mine i think someone has previously used a black silcone sealant to stick the filter to the hollow spindle , but sealant had entered the tube . I used a 2.5mm drill to fetch most of it out the tube and then some WD40 softened the rest .. I have a litle vacuum hand pump for testing for leaks and applying this to the spindle sucked out the rest of the gunk.

Whilst it was off i tested the operation with a 12v supply and when energised, the lower spout (vacuum source from the throttle plate) is connected and open to the upper spout going to the EGR valve actuator.
On de-energise the vacuum supply port is shut and the upper port (to EGR actuator ) is opened and connected to atmosphere via the vent through the hollow spindle.

The little black vent cap was also blocked in the central port - cleared now with WD40 and a pipe cleaner .

To hold the vent filter to the now , i've a piece of silicone hose .

I am convinced that this blockage has caused the EGR to stay open at all times and played havoc with the manifold vacuum at idle .

EGR solenoid1.JPG

Thanks

Charlie

[chrisP]

Slight update from me , well it looked like it was partially down to the ERG valve and cleaning it out and testing helped a lot.

You can test it in situ by putting a hose on the ERG valve connector and sucking - the vacuum required is minimal.

But I am now back to the hard start situation, which I think might be the loom as I have tried everything else.

[Chas54]

Chris

I dont dont know if you checked the little EGR solenoid vent to atmosphere but i am certain its caused me some problems .

If its blocked it will trap the vacuum in the line between the solenoid and EGR valve actuator therebuy holding it slightly open .

I figure that removing the vacuum pipe to the actuator releases the trapped vacuum and allows the EGR valve to close . Next time you start the car all seems good . You run the car about and at the required temperature and revs etc , the solenoid opens the vacuum to the EGR as it should. Next time you come to an idle,the revs are uneven as the trapped vacuum holds the EGR valve open . This is because the solenoid valve vent is blocked . Next time you try to start its a bitch to keep it running as the manifold vacuum is poor because the EGR is open .
This was the case with mine and you identified it with your initial description.

regards
Charlie

[tigerdog]

This is a brilliant thread - many thanks for a deep dive into obscure minutiae that likely impacts many cars given their age. Well done!

[chrisP]

Hi Charlie
Thank you for the comments, it looks like you could be on to something here!

I again disconnected the vacuum to the ERG valve and blocked the pipe. Then over the past few days have been randomly starting the car, 9 times out of 10 it used to be a hard start, now it seems to be on the first half a second. The car idles for a second or so and then dies, so I don't know if there is enough of a leak in the pintle of the ERG valve to cause this - so hopefully today I will make a blanking plate to see.

The Denso vacuum valve appears to be in good condition, with no sign of blockage.

Will report back.......
Best Regards
Chris