idle '77 Fuel Injection

BusBerd · Posted: Fri Apr 20, 2007 10:09 am Post subject: idle '77 Fuel Injection

on a cold start my bus really struggles with a low idle (almost dying) until it warms up. I thought it may be the Aux Air Regulator, but I replaced it with a new one and I am still having problems.

My idle use to shoot up to 2000rpm when warm, but I recently set the idle at 850(+-75)rpm when the engine was fully warm, so now my idle at "cold start-up" struggles considerably, but when fully warm the idle is ok, I think.

My thoughts are to check the power coming to the AAR valve. Does that come through the double relay? should I check something on the double relay as well??

Also in my "idle" search here in the forum, someone mentioned checking the gap of the spark plugs. I have never done that to my plugs, but I have changed them a few times in the life of my bus. I always thought they were pre-gapped. do i need to gap them?

Would a vacuum leak create this low idle at a cold start that eventually creeps up?I don't know if this is related, but when I take the vacuum hose of the Distributor (SVDA) there is no change in the engine and i feel no vacuum in the hose. I tried revving the engine with the hose off and my finger over the hole in the hose, but felt very little, if any, vacuum. That doesn't seem right to me. On my '71 bus (with a 34PICT3 carb), if I do that at the distributor, the engine will die unless I cover the vacuum hose with my finger. and i can definitely feel the vacuum.

HELP! I would love to have a smooth idle from cold to warm.
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

VWBusrepairman · Samba Member Joined: July 06, 2004 Posts: 4726

To get a warm idle, did you have to screw the idle screw all the way in? Maybe it's too far in and it's cutting off the air supply at cold throttle? This is a condition I'm noticing on my engine as well. To help, I too replaced my Aux. Air valve, but also put hose clamps on the cracked hose and filled the cracks with some sealant...

How are the 4 braided hoses on the air plenum? Maybe it's drawing in false air from some where?

BusBerd · Posted: Fri Apr 20, 2007 10:32 am Post subject:

I think the hoses are ok. I replaced them. But would a vacuum leak cause the idle to creep up as the engine gets warmer?
what about the no-vacuum issue at the dizzy?
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

VWBusrepairman · Samba Member Joined: July 06, 2004 Posts: 4726

Randy in Maine · Posted: Fri Apr 20, 2007 11:30 am Post subject:

I think the bentley has a method for determining if the thermotime switch is actually working in order to tell the CSV to give you a squirt when the engine is cold.

2VWs1BMW · Posted: Fri Apr 20, 2007 11:36 am Post subject:

also take a look at your cylinder head temp sensor. they tend to go south after a while.

when I DD'd my bus, I replaced it once a year.
_________________
- Brian -
'17 Alltrack
'99 ///M Coupe w/48k mi - Bimmerforums
'77 Westy w/156k mi

VWBusrepairman · Samba Member Joined: July 06, 2004 Posts: 4726

The cylinder head temp sensor is critical to good engine performance, particularly during starting and warm-up.

The cold start valve can be checked by hot wiring the valve and watching the change in fuel pressure on the gage.

for the thermo-time sw. - operate starter, test light connected on the cold start valve harness should go on for several seconds and then go out if the thermo-time sw. and harness are OK. Hope this helps!

BusBerd · Posted: Fri Apr 20, 2007 3:07 pm Post subject:

Thanks for the help guys!

2VWs1BMW · Posted: Fri Apr 20, 2007 4:31 pm Post subject:

Randy in Maine · Posted: Fri Apr 20, 2007 4:49 pm Post subject:

VWBusrepairman · Samba Member Joined: July 06, 2004 Posts: 4726

BusBerd · Posted: Sat Apr 21, 2007 2:40 pm Post subject:

Randy in Maine · Posted: Sat Apr 21, 2007 3:10 pm Post subject:

Just plunk your volt ohm meter on the wiring harness. that will tell you the voltage right now.

BusBerd · Posted: Fri May 11, 2007 7:28 am Post subject:

Just to wrap this thread up, I'll post the my fix of the idle.

Well, I just got my temp sensor II in the mail a few days ago.

Image may have been reduced in size. Click image to view fullscreen.

I took out my old one and put the new one in and it idles great now. I really didn't think it was going to make a difference, but I was wrong. thankfully.

It was an easy fix.

Thanks to all for your help and insight!
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

Randy in Maine · Posted: Fri May 11, 2007 8:41 am Post subject:

Suggestion: Always keep a new spare Temp Sensor II in your tool box. they are cheap to buy and have as a spare.

The old ones will also bench test "OK" when they are really "bunk".


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