vacuum leaks- how do they affect system?

crowinghen

We're trying to find the culprit to our van's intermittent hesitation and surging while driving at operating temps.
Our vacuum lines are loose in a lot of different locations- they pull out super easily .
Could this be the reason or part of the reason for our issues?
of course we're going to replace them but just curious as to how this could be affecting the van's performance.
thanks,
Susie
_________________
1984 Westfalia a work in progress " Butters"

Glenn

Californio · Samba Member Joined: May 17, 2007 Posts: 1305

The vacuum controls things like fuel pressure, which is reduced on high vacuum/idle conditions, and your ignition advance. In my experience it's important but not absolutely critical, ie., not a show-stopper. If you remove a vacuum hose entirely, the engine will still run, if all the rest is in good working order.

I haven't had a wbx in some years, but if I remember right, there are some flow restrictors in the oem configuration that are worth paying attention to. I'm sure others will know more than I on this.

crowinghen · Posted: Sun Jan 16, 2011 4:20 pm Post subject:

Well it runs, but after warm-up it hesitates/surges and the idle gets rougher.
Yeah I saw that there are some flow restrictors in the Bentley-- we'll make sure they are still intact.

will report back-- thanks!
_________________
1984 Westfalia a work in progress " Butters"

crowinghen · Posted: Sun Jan 16, 2011 7:11 pm Post subject:

Got the vacuum lines changed-- no difference in engine performance.
darn!
Susie
_________________
1984 Westfalia a work in progress " Butters"

heidi85ho · Posted: Mon Jan 17, 2011 6:58 am Post subject:

susie, try bypassing the idle stabilizer control box. plug the two wires that go into it together. see if that makes any difference.

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50338

Double check your TPS as well. If the switch is poorly adjusted or just plain dying it will cause all kinds of weird sputtering.

crowinghen · Posted: Mon Jan 17, 2011 9:18 am Post subject:

crowinghen · Posted: Mon Jan 17, 2011 9:36 am Post subject:

Californio · Samba Member Joined: May 17, 2007 Posts: 1305

The first thing I would do is make sure the basics are there. You've probably done a lot of this, but make sure the grounds are all clean, and methodically go through the Bentley FI system diagnosis. When you pull the ECU plug for the diagnosis, clean the pins with contact cleaner before putting it back.

Make sure to check the green coaxial cable that runs to the O2 sensor. Very important because if this shorts you will not be getting a signal to the ECU.

Also, if you have ever opened and adjusted the AFM, take it to a shop and have it recalibrated at various RPM with a sniffer. You cannot do this yourself. It shouldn't cost more than $50 or so and makes a world of difference if your present one is out of whack. When I had a wbx I considered this the best $50 ever spent on it. Make sure it is a Vanagon shop, not just a smog guy, too.

Unless there is a massive vacuum leak, you usually won't see much difference.

crowinghen · Posted: Mon Jan 17, 2011 11:17 am Post subject:

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50338

Using a digital multimeter you should get a voltage from the O2 sensor when the engine is hot and running. Also make sure that the wire coming through the harness to the O2 sensor isn't grounded out.

r39o · Posted: Mon Jan 17, 2011 11:47 am Post subject:

Jamsbondman · Posted: Mon Jan 17, 2011 11:53 am Post subject:

Hey just wanted to let you know I have a rebuilt AFM that was newly rebuilt a year ago. My van has recently had some running issues and I narrowed it down to the AFM going bad. Now it didn't go bad as in having flat spots or voltage drops from a dirty wiper arm. I found that it was bad by installing a good used AFM and my problems disappeared immediately. I have bench tested it and tested the year old one on the car and it seems to function normally but on the car my van will hesitate and have a lack of power after warmed up. When the engine is cold it runs extra rich so the car is fine but once it wars up and the car leans out to normal range it shows problems. I have tried to get the AFM to match the good working AFM by measuring voltage output at idle flow and high volume flow but even though the output voltage will match pu it in the car and its hesitation and poor power returns. Just see if you have a friend that has a used AFM and try it in your van to see if it makes a difference.

crowinghen · Posted: Mon Jan 17, 2011 2:00 pm Post subject:

crowinghen · Posted: Mon Jan 17, 2011 5:14 pm Post subject:

crowinghen · Posted: Mon Jan 17, 2011 5:21 pm Post subject:

Got the Cat convertor off-- and guess what-- it's already been hollowed out before us! so guess that's not the problem.
While doing a test for the cat convertor we did notice something that might be helpful.

We tested the vacuum at idle, it was around 13 ( I can't remember the exact number) so we were to increase idle to 3000 rpm and watch the vacuum gauge. So hubby held the throttle steady and it did the same symptoms we have when driving :bogs down, then surges forward. the vacuum dropped momentarily, then went up. say to like 23 and gradually would get less, then change with the surging/hesitation of the motor.

so does this tell us anything???
I'm starting to think that we have to go back to the basics- check the injectors, plugs, etc, follow the Bentley FI guide.
Also with the catalytic convertor being hollowed out, I don't believe we are the first people to go down this road with this van ( pun intended)

hmmm... Susie

Just putting my thoughts out here, it helps me to get things straight in myhead... but if anyone wants to chime in feel free!
_________________
1984 Westfalia a work in progress " Butters"

plummerdesign · Posted: Mon Jan 17, 2011 9:10 pm Post subject:

Susie,

Just read through this thread and it sounds all too familiar. (This was back in 1998 on my white 1984 Westy.) Same symptoms lead me to change vacuum lines and oxygen sensor. No fix.
Cat was good so did tune up, injector cleaning and so on. No fix.
Took rig to Dennis and Jim at Sports Car Center in Portland. They changed out the AFM and all was good. Fixed.
.
Same fix for you? Not sure. The notion of a “donor” AFM is a great idea.
Cheers,
Jeffery
_________________
It is old and green and it makes me grin.
1984 Westfalia 1.9

Californio · Samba Member Joined: May 17, 2007 Posts: 1305

You can't test an AFM. The test in the Bentley isn't accurate enough to tell you anything.

Even if you put on a new or rebuilt AFM, it needs to be calibrated. This can only be done with a sniffer. A word to the wise...

r39o · Posted: Mon Jan 17, 2011 9:38 pm Post subject:

OK. My 85 had lots of issues when I got it. The last being some running related bucking. The AFM was *THE* last thing I messed with. That was done LAST. Last after everything else. Keep reading....

Your black exhaust tells me you are running rich. You can run rich by 3 different things:

1. Throttle body switches
2. Sensor II (coolant temp - the common one we all replace)
3. Sensor I (air temp sensor in the AFM)

I will assume you have verified or replace items 1 and 2. Three is tested with an ohm meter at the AFM and then at the ECU. So be sure of those things FIRST.

Second, besides the O2 sensor (which usually only will be slow to respond rather than dead) should categorically replaced (find the cheap Bosch generic and splice and solder the single wire. Don't get anti sieze on the tip or use Silicon spray to lube - all bad for the O2 sensor.)

So now for the final and last tricky part. This is not simple. It is how I calibrated my AFM. There are more ways too. But this worked for me. In my case I used a very expensive test box from back in the day - only scant few people have these and my good friend had one which I used before he retired and took it with him for his 85 Westy Weekender. So here ya go.

I do NOT claim this will help you. It worked for me as a final tune. YMMV!

Warm engine up
Turn off engine.
Unplug AFM
Use a variable resistor to simulate the AFM and adjust for best idle by ear.
Note the voltage going into the ECU.
Turn off engine
Plug the AFM in.
Start engine.
Adjust the AFM to produce the same voltage.
Done.

Best your AFM is going to get unless you follow the FAQ posts and reset your track and wiper arm in the AFM. Tricky business.

Didn't Van-Cafe.com have new replacement AFMs? Or Bus Depot?
_________________
"Use the SEARCH, Luke" But first visit the Vanagon FAQ!

1990 Multivan EJ 22, Rancho trans 0.82 4th, Small Car front AC, CLKs w/ 215/65-16, homemade big brakes 303mm, Konis, Recaros, etc....

Click to see my ads for Cup holders, Subaru clutch fix and CLK wheels (no wheels currently)


Hello! Log in or Register \| Help \| Donate \| Buy Shirts	See all banner ads \| Advertise on TheSamba.com

	Forum Index -> Vanagon	All times are Mountain Standard Time/Pacific Daylight Savings Time
Page 1 of 1