VR6 idle stablilisation valve disconnected - car runs better?

[Reverend Frog 10]

My 1993 VR has been conking out at junctions since I got it, so I did the usual ISV clean out this morning (didn't seem to be too dirty, plus not sure I did this part properly - just squirted brake cleaner in and shook it about).

 

Lo and behold the car now idles beautifully at junctions...but i just realised that i forgot to hook up the electrical connector on the end when I was refitting it. The car seems to be running fine without it, so I might leave it alone for the time being. is there any problem with doing this?

 

Thanks

[DPS 10]

Ive just posed about the same problem BUT mine is 94 and typically, if I unplug the ISV she won't start as the ECU appears to depend on it :scratch:

 

Its the same if I unplug the MAF, the car dies.

 

Anyway good luck with your resolution, I hope it's easier to resolve than mine has been so far!

 

Dawn

[pbradley98 0]

When disconnected it holds the value open slightly, so you get some airflow through it - guessing it may idle slighty fast or slow it it's not being controlled at all?

[Reverend Frog 10]

it's probably too low on cold start, and gear changes are slightly lumpy for a few minutes, but it's worth it to have a car that doesn't cut out

 

what does the electrical connector actually connect to? and am I doing any harm by having it disconnected?

[Jim Bowen 1]

It has a little motor type affair in it, it makes an opening smaller or larger. I think if its faulty the car will use other sensors to work out an idle speed, which ends up being a bit higher than normal.

[Jim Bowen 1]

Just thinking you may need to reset the ecu.

[Reverend Frog 10]

Just thinking you may need to reset the ecu.

 

How'd you do that Jim?

 

i think the car's lambda sensor wiring has been buggered about with in the past, and the MFA shows nothing for MPG or oil temp (if that is of any relevance)

[Jim Bowen 1]

I think you just leave the battery disconnected for a while so ECU forgets

[Jim Bowen 1]

There is a procedure for it somewhere on the forum

[Jim 1]

http://wiki.the-corrado.net/vr6_ecu_reset_procedure.html

[Kevin Bacon 5]

What idle speed are you getting?

 

If the car is idling perfectly with the ISV disconnected, have a look to see if a previous owner has tampered with the throttle body to hold it open more than standard. If the yellow tamper proof paint on the throttle stop screw has been disturbed, it's a good sign.

 

By default, the throttle blade is fully closed at idle and with no ISV, the engine struggles to hold a good idle speed when it's really hot. As mentioned, the valve is never fully shut and it may be holding 680rpm from just the gap (or with the throttle cracked off it's stop slightly) because of the relatively cold & dense air, but there will come a time when it will just simply stall if it's not connected. For example, when sat in traffic for ages the engine will need an air flow boost from the ISV to maintain the idle.