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vacuum leaks- how do they affect system?
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crowinghen
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PostPosted: Sun Jan 16, 2011 3:49 pm    Post subject: vacuum leaks- how do they affect system? Reply with quote

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
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Glenn Premium Member
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PostPosted: Sun Jan 16, 2011 3:51 pm    Post subject: Re: vacuum leaks- how do they affect system? Reply with quote

crowinghen wrote:
Could this be the reason or part of the reason for our issues?

Yes they could be, replace them and report back.
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Californio
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PostPosted: Sun Jan 16, 2011 4:06 pm    Post subject: Reply with quote

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.
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crowinghen
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PostPosted: Sun Jan 16, 2011 4:20 pm    Post subject: Reply with quote

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!
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crowinghen
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PostPosted: Sun Jan 16, 2011 7:11 pm    Post subject: Reply with quote

Got the vacuum lines changed-- no difference in engine performance.
darn!
Susie
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PostPosted: Mon Jan 17, 2011 6:58 am    Post subject: Reply with quote

susie, try bypassing the idle stabilizer control box. plug the two wires that go into it together. see if that makes any difference.
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Wildthings
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PostPosted: Mon Jan 17, 2011 7:01 am    Post subject: Reply with quote

Double check your TPS as well. If the switch is poorly adjusted or just plain dying it will cause all kinds of weird sputtering.
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crowinghen
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PostPosted: Mon Jan 17, 2011 9:18 am    Post subject: Reply with quote

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

Thanks- we tested the switches and the adjustment-- it's reading like it should and the adjustment is what the Bentley says it should be.
so unless it's intermittently not working I think we can rule those out.
thanks though!
Susie
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PostPosted: Mon Jan 17, 2011 9:36 am    Post subject: Reply with quote

heidi85ho wrote:
susie, try bypassing the idle stabilizer control box. plug the two wires that go into it together. see if that makes any difference.

We've tried that in the [ast, but will try it again... I tend to think it's not that because it runs well when it's cold,but worsens as it gets warm.
We just put in anew oxygen sensor and it made a difference at first. Yesterday we unplugged it and it ran the same as when it's plugged in, so perhaps we got a bad sensor or the wires are messed up. I think we'll just replace it and see what happens.
aLso our engine is sounding kind of wheezy-- so we're looking at the catalytic converter...
so the quest continues!!

Thanks for any input!
Susie

edited because I'm not the best typist
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Last edited by crowinghen on Mon Jan 17, 2011 11:19 am; edited 1 time in total
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Californio
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PostPosted: Mon Jan 17, 2011 10:20 am    Post subject: Reply with quote

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.
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crowinghen
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PostPosted: Mon Jan 17, 2011 11:17 am    Post subject: Reply with quote

Californio wrote:
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.

Thanks- we've tested our afm and it responds as it should... we're in the process of looking at the o2 sensor wires but so far haven't come up with the testing method-- (haven't really delved into this yet)
thanks, Susie
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PostPosted: Mon Jan 17, 2011 11:36 am    Post subject: Reply with quote

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.
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PostPosted: Mon Jan 17, 2011 11:47 am    Post subject: Reply with quote

crowinghen wrote:
Thanks- we've tested our afm and it responds as it should...

So you think? You can have a bad spot on the track which only is noticed during the vibrations associated with driving. Look in the Best Threads link in my signature below to find out about the afm.

Did you check your fuel pressure? How's the pump? Noisy?

When was the last time the fuel filter was changed?

Is your tank rusty?

Crappy spray patterns from injectors can do the same thing.

You have a fuel ignition problem at high rpm.

Look up causes of surging.

At higher revs simple things like a worn throttle body or minor intake leaks just do not mean that much. But a lean mixture, for example will.

How's your fuel economy?

How does your tail pipe look? Brown, black, gray?

Have you taken a valid spark plug reading?

Do you have any exhaust issues like holes, leaks or restrictions?

This is an 84 which is approaching the 3 decade mark. LOTS of stuff can be up with a van with that amount of time on the life clock? There's just all sorts of stuff!

Good luck!
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PostPosted: Mon Jan 17, 2011 11:53 am    Post subject: Reply with quote

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.
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crowinghen
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PostPosted: Mon Jan 17, 2011 2:00 pm    Post subject: Reply with quote

r39o wrote:
crowinghen wrote:
Thanks- we've tested our afm and it responds as it should...

So you think? You can have a bad spot on the track which only is noticed during the vibrations associated with driving. Look in the Best Threads link in my signature below to find out about the afm.

Well we teted it as it says in the Bentley and it tested fine... Yes I understand it could act differently when actually running, but really don't know how to test it live.


Did you check your fuel pressure? Fuel pressure was low, replaced fuel pressure regulator How's the pump? Noisy? quiet

When was the last time the fuel filter was changed? 1 month ago

Is your tank rusty? no

Crappy spray patterns from injectors can do the same thing. Haven't checked them

You have a fuel ignition problem at high rpm.

Look up causes of surging.

At higher revs simple things like a worn throttle body or minor intake leaks just do not mean that much. But a lean mixture, for example will.

How's your fuel economy? Don't know we haven't driven it that long/far

How does your tail pipe look? Brown, black, gray? black

Have you taken a valid spark plug reading? no

Do you have any exhaust issues like holes, leaks or restrictions? Not that we can find-- we're checking the catalytic convertor today

This is an 84 which is approaching the 3 decade mark. LOTS of stuff can be up with a van with that amount of time on the life clock? There's just all sorts of stuff!

Good luck!
thanks for the luck-- that's a daunting list.
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crowinghen
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PostPosted: Mon Jan 17, 2011 5:14 pm    Post subject: Reply with quote

Jamsbondman wrote:
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.


Yes this would be great! I'll start another post


susie
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PostPosted: Mon Jan 17, 2011 5:21 pm    Post subject: Reply with quote

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!
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PostPosted: Mon Jan 17, 2011 9:10 pm    Post subject: Reply with quote

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
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PostPosted: Mon Jan 17, 2011 9:22 pm    Post subject: Reply with quote

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...
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PostPosted: Mon Jan 17, 2011 9:38 pm    Post subject: Reply with quote

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?
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