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Wildthings Samba Member

Joined: March 13, 2005 Posts: 51685
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Posted: Wed Dec 25, 2024 9:35 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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chrmcc wrote: |
SGKent wrote: |
if it is still FI, which is implied by your subject line, do a cylinder balance test to see if all 4 are firing evenly, then check the TSII. I would not have jumped to timing as the cause. |
Thanks for the suggestion, coincidentally I looked at both those items this past week.
I checked the sensor, not very scientifically but it seemed to be working, for good measure I replaced it, no noticeable change.
Also, not very scientific, but I pulled each plug and didn’t notice much difference in an one cylinder.
Bill rebuilt the original distributor for me, I’ll try to dial it in once I have it hand.
In the meantime I’m inspecting vacuum lines and checking the fuel pressure. |
With the engine warm, if you disconnect the wire to the TSII sensor the engine should instantly begin to run poorly and maybe even die. If nothing happens when you disconnect it, then it or its wiring is bad. |
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SGKent  Samba Member

Joined: October 30, 2007 Posts: 41343 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Dec 24, 2024 11:52 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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chrmcc wrote: |
SGKent wrote: |
if it is still FI, which is implied by your subject line, do a cylinder balance test to see if all 4 are firing evenly, then check the TSII. I would not have jumped to timing as the cause. |
Thanks for the suggestion, coincidentally I looked at both those items this past week.
I checked the sensor, not very scientifically but it seemed to be working, for good measure I replaced it, no noticeable change.
Also, not very scientific, but I pulled each plug and didn’t notice much difference in an one cylinder.
Bill rebuilt the original distributor for me, I’ll try to dial it in once I have it hand.
In the meantime I’m inspecting vacuum lines and checking the fuel pressure. |
Good choices. Generally if the timing is off a few degrees, the engine is not going to smell rich. That implies either too much fuel, or cylinders are not firing. A miss at idle can be either from too rich or too lean. One common issue in the FI buses is that the fuel injector seals crack and get loose, allowing air to enter and cause a lean miss.
Sooty black plugs do imply a really rich mixture, which could be a bad fuel regulator. Another cause that would affect all the cylinders would be a leaking CSV. _________________ "Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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chrmcc Samba Member

Joined: April 29, 2022 Posts: 34 Location: Houston, TX
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Posted: Tue Dec 24, 2024 5:36 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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SGKent wrote: |
if it is still FI, which is implied by your subject line, do a cylinder balance test to see if all 4 are firing evenly, then check the TSII. I would not have jumped to timing as the cause. |
Thanks for the suggestion, coincidentally I looked at both those items this past week.
I checked the sensor, not very scientifically but it seemed to be working, for good measure I replaced it, no noticeable change.
Also, not very scientific, but I pulled each plug and didn’t notice much difference in an one cylinder.
Bill rebuilt the original distributor for me, I’ll try to dial it in once I have it hand.
In the meantime I’m inspecting vacuum lines and checking the fuel pressure. _________________ Thanks in advance!
Chris McC
78 VW Sunroof Bus - mostly stock 2000cc FI
99 Porsche 996 Cab - stock 3.4 flat six |
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SGKent  Samba Member

Joined: October 30, 2007 Posts: 41343 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Dec 24, 2024 11:29 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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if it is still FI, which is implied by your subject line, do a cylinder balance test to see if all 4 are firing evenly, then check the TSII. I would not have jumped to timing as the cause. _________________ "Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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chrmcc Samba Member

Joined: April 29, 2022 Posts: 34 Location: Houston, TX
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Posted: Tue Dec 24, 2024 11:14 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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skills@eurocarsplus wrote: |
chrmcc wrote: |
Yes, I have an aftermarket aluminum scale, the original plastic broke into several pieces. Can you still find the more accurate plastic scales? |
yea, those are pretty horrible
here is a good breakdown
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
I'd be looking for an original one myself |
That's a great thread. I have the exact POS shown from Bud Depot, how hard is it to make an accurate aftermarket scale?
The search begins. Thanks. _________________ Thanks in advance!
Chris McC
78 VW Sunroof Bus - mostly stock 2000cc FI
99 Porsche 996 Cab - stock 3.4 flat six |
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skills@eurocarsplus Samba Peckerhead

Joined: January 01, 2007 Posts: 17628 Location: sticksville, ct.
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Posted: Tue Dec 24, 2024 10:45 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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chrmcc wrote: |
Yes, I have an aftermarket aluminum scale, the original plastic broke into several pieces. Can you still find the more accurate plastic scales? |
yea, those are pretty horrible
here is a good breakdown
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
I'd be looking for an original one myself _________________
gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
Jake Raby wrote: |
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
Brian wrote: |
Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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Wildthings Samba Member

Joined: March 13, 2005 Posts: 51685
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Posted: Tue Dec 24, 2024 10:22 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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If you haven't done it yet add some FI cleaner to your fuel tank and see what happens. |
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chrmcc Samba Member

Joined: April 29, 2022 Posts: 34 Location: Houston, TX
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Posted: Tue Dec 24, 2024 7:59 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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Bill Schwimmer wrote: |
I am curious if you have one of the aluminum aftermarket timing scales. I chased my tail for a bit timing my bus. I matched up an OE plastic scale to it. And they are wayyyy off to the retarded side. |
Yes, I have an aftermarket aluminum scale, the original plastic broke into several pieces. Can you still find the more accurate plastic scales? _________________ Thanks in advance!
Chris McC
78 VW Sunroof Bus - mostly stock 2000cc FI
99 Porsche 996 Cab - stock 3.4 flat six |
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chrmcc Samba Member

Joined: April 29, 2022 Posts: 34 Location: Houston, TX
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Posted: Mon Dec 09, 2024 4:24 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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raygreenwood wrote: |
skills@eurocarsplus wrote: |
raygreenwood wrote: |
...IF...centrifugal advance is kicking in due to the high idle. |
assuming (and I know better than to do that) everything was ok before the pertronix install, I feel that this is what is happening.
The advance is coming in early due to a garbage part. but, it would 100% make sense to make sure the whole system is (vacuum) leak free
and, I'll echo the timing scale thing. make sure you have a legit scale otherwise you're just never going to get things right |
I would buy that.....but its not clear yet. It "sounds" like he put the P-tron in and drove it for a while no problems. And yes, with a little age it could have shit the bed.
But.....while for sure the P-tron crapping out could cause high idle timing....it's not likely to cause heavy enrichment.
Yes.....we could speculate that the rich reading on the plugs is due to poor ignition....poor spark.....maybe a weak coil? But there would also be a lot more running problems.
This started two years ago when he replaced the old distributor....and he is just noticing now?
My bet is that this thing has not been driven much or sat for a year plus. That sitting still alone is a killer on the FPR.
Ray |
It ran well after I installed the ptron distro, I replaced the coil at that time as well, also ptron. Setting the timing at that time was a pain from what I recall.
My dad did not drive it much the last few years, since I have had it I usually make short trips a couple times a week and try to get out for a good highway run once a month.
It gradually stated running a bit rough, but the exhaust was becoming unbearably strong. That is what really made me start looking at it, I should have picked up on the idle creeping up sooner but didn't notice until I started trying to figure out why it was running rich.
in the original post I mentioned what I have done, it's running decent again and does not seem to as rich but I only have a small sample size.
There is no vacuum on the line coming to the distro while at idle. There are no obvious vacuum leaks, I checked at all the hose fittings.
I will check the fuel pressure and look for vacuum leaks in the areas suggested.
I will probably go back to an original distro and points. Between what I have read here and other places, the pertronix was probably a bad decision.
I appreciate everyone's input and suggestions. I enjoy driving and working on it so I want to learn more. _________________ Thanks in advance!
Chris McC
78 VW Sunroof Bus - mostly stock 2000cc FI
99 Porsche 996 Cab - stock 3.4 flat six |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 22600 Location: Oklahoma City
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Posted: Mon Dec 09, 2024 3:32 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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skills@eurocarsplus wrote: |
raygreenwood wrote: |
...IF...centrifugal advance is kicking in due to the high idle. |
assuming (and I know better than to do that) everything was ok before the pertronix install, I feel that this is what is happening.
The advance is coming in early due to a garbage part. but, it would 100% make sense to make sure the whole system is (vacuum) leak free
and, I'll echo the timing scale thing. make sure you have a legit scale otherwise you're just never going to get things right |
I would buy that.....but its not clear yet. It "sounds" like he put the P-tron in and drove it for a while no problems. And yes, with a little age it could have shit the bed.
But.....while for sure the P-tron crapping out could cause high idle timing....it's not likely to cause heavy enrichment.
Yes.....we could speculate that the rich reading on the plugs is due to poor ignition....poor spark.....maybe a weak coil? But there would also be a lot more running problems.
This started two years ago when he replaced the old distributor....and he is just noticing now?
My bet is that this thing has not been driven much or sat for a year plus. That sitting still alone is a killer on the FPR.
Not saying you are wrong about the distributor being shit. But, I think he should check the basic before he swaps anything in or out and most especially before he starts tweaking with the AFM.
Ray |
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skills@eurocarsplus Samba Peckerhead

Joined: January 01, 2007 Posts: 17628 Location: sticksville, ct.
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Posted: Mon Dec 09, 2024 3:10 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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raygreenwood wrote: |
...IF...centrifugal advance is kicking in due to the high idle. |
assuming (and I know better than to do that) everything was ok before the pertronix install, I feel that this is what is happening.
The advance is coming in early due to a garbage part. but, it would 100% make sense to make sure the whole system is (vacuum) leak free
and, I'll echo the timing scale thing. make sure you have a legit scale otherwise you're just never going to get things right _________________
gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
Jake Raby wrote: |
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
Brian wrote: |
Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 22600 Location: Oklahoma City
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Posted: Mon Dec 09, 2024 1:25 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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In my last comment I said that a vacuum leak would bypass air past the AFM flap and cause a "lean condition" and not the rich condition you are gettintg.
That is both correct and incorrect. Let me clarify please.
On this crude diagram, IF....you have a vacuum leak that is leaking anywhere BETWEEN the AFM aand the OUTSIDE of the throttle body (TB)....that air bypasses the AFM and gerts no fuel assigned to it so it WILL cause a lean condition.
This would NOT cause your black spark plug or your excessive idle timing issue.
HOWEVER:
If you have a vacuum leak into the intake system DOWNSTREAM/inboard of the TB....while this will still bypass air around the AFM...causing a lean condition of some level (could be big or small depending on the vacuum leak size).....because the air leak is actually on the HIGH VACUMM side of the TB....it can cause several other issues.
1. The leak I first described (between the AFM and TB) only affects fuel mixture. It does not affect VACUUM level.
2. The second type of air leak (downstream of the TB)...simultaneusly affects fueling by bypassing the AFM (lean input) but it also reduces vacuum.
This mimics a "throttle open" position. You are getting air past the throttle flap. While one might see that still as lean....the actual vacuum leak CAN or WILL affect the vacuum operated fuel pressure regulator.
At idle with no vacuum leaks, the rising rate fuel pressure regulator should give you about 28 psi. When you open the throttle and vacuum bleeds off you can get up to 36 psi of fuel pressure.
If you are idling and 29 psi of fuel pressure is what you should have...that is considered "100%" at idle. This means that every 1 = 3.517% of your fuel mixture.
So if you have a vacuum leak at idle on the inboard side of the TB....lets say you are at 36 psi when you should be at 29 psi. ...thats 7 psi too high ...with each 1 psi worth 3.517%....you could easily be 24.6% too rich across the board at idle.
So....with a small amount of extra air leaking in AND extra fuel being added in because of that vacuum loss....you would easily see a rich burn, higher idle speed and higher idle timing...IF...centrifugal advance is kicking in due to the high idle.
A quick check. At idle, pull the vacuum hose off of the advance unit. If the idle timing drops down again...and/or you feel suction at that small vacuum hose....then either your throttle is not closing all the way or the throttle plate is worn out. With the throttle plate fully closed there should be no vacuum advance signal.
Next check. Put a gage on the fuel rail. If yoyur fuel pressure is higher than 28-29 psi at idle....well...you have found the issue. To find out why....Take a hand vacuum pump and apply vacuum to the fuel pressure regulator while idling. If the pressure drops to 28-29 you have verified that the regulator is working.
Start checking for vacuum leaks now. Check the 0-ring between TB and plenum, runner boots, injector seals, and vacuum line or gasket to the intake plenum all the way to the gaskets between runner and cylinder head.
Ray
Last edited by raygreenwood on Mon Dec 09, 2024 5:06 pm; edited 1 time in total |
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skills@eurocarsplus Samba Peckerhead

Joined: January 01, 2007 Posts: 17628 Location: sticksville, ct.
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Posted: Mon Dec 09, 2024 11:36 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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^^^
this guy gets it  _________________
gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
Jake Raby wrote: |
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
Brian wrote: |
Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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mikedjames Samba Member

Joined: July 02, 2012 Posts: 3132 Location: Hamble, Hampshire, UK
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Posted: Mon Dec 09, 2024 11:28 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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With ported vacuum if the throttle plate covering the hole is slighly uncovering it at " idle, " the ported pressure drops from atmospheric as the hole is uncovered down to about half atmospheric.
So messing with the throttle endstop screw to fix a different problem causes too much advance at idle, made worse by the engine running faster and winding on centrifugal advance.
The $15 China distributors are made to have more maximum advance than a Bosch. Because that makes them seem more exciting.
My China distributor is sawn off and used as a No1 indicator for setting valves alongside crank fire system. Best use for a Chinese part... _________________ Ancient vehicles and vessels
1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.
1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy |
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Wildthings Samba Member

Joined: March 13, 2005 Posts: 51685
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Posted: Mon Dec 09, 2024 9:24 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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Bill Schwimmer wrote: |
I am curious if you have one of the aluminum aftermarket timing scales. I chased my tail for a bit timing my bus. I matched up an OE plastic scale to it. And they are wayyyy off to the retarded side. |
I put marks on my fan shroud decades ago that shows TDC and 7.5° BTDC as determined by using a piston stop. I have a plastic scale and can easily verify it by comparing it to the mark on the shroud and time the engine even if the scale were to be damaged. |
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Bill Schwimmer Samba Member
Joined: February 12, 2004 Posts: 86
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Posted: Mon Dec 09, 2024 8:29 am Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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I am curious if you have one of the aluminum aftermarket timing scales. I chased my tail for a bit timing my bus. I matched up an OE plastic scale to it. And they are wayyyy off to the retarded side. |
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heimlich  VWNOS.com

Joined: November 20, 2016 Posts: 7271 Location: Houston, Texas
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Posted: Sun Dec 08, 2024 9:11 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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Wildthings wrote: |
The stock distributor has two return springs for the centrifugal weights, one uses thin wire and a tight coil and is under tension at all times. The second one uses larger wire and has a loose coil and is not under tension until the centrifugal timing has already advanced by 10° or so. Your symptom could be because the spring with the smaller diameter wire either broke or came off it's pegs.
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This is another common problem. Usually, you will see the timing jumping around because of this. _________________ www.vwnos.com [email protected]
Classic Brands. Classic Quality.
Not all parts are made the same. NOS OE/OEM parts made mainly in West Germany, Early Germany, and Early Brazil are where VW produced the best quality parts and best fitting products.
5% Off your order with coupon code: 5%OFF
Restored Distributors Available (<--Click here) |
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Wildthings Samba Member

Joined: March 13, 2005 Posts: 51685
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Posted: Sun Dec 08, 2024 8:11 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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The stock distributor has two return springs for the centrifugal weights, one uses thin wire and a tight coil and is under tension at all times. The second one uses larger wire and has a loose coil and is not under tension until the centrifugal timing has already advanced by 10° or so. Your symptom could be because the spring with the smaller diameter wire either broke or came off it's pegs.
I agree with others that the Pertronix distributors are trash. I thought nearly twenty years ago that this might be a good way to get around the problem with low quality Bosch points so bought one, it pretty much had problems right out of the box so I got the vendor to send me another one which also had problems right out of the box, so I sent them both back and installed a Pertronix ignition module in my old distributor, but it failed after a few months so some non Bosch points went in anf I have had no problems since. |
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skills@eurocarsplus Samba Peckerhead

Joined: January 01, 2007 Posts: 17628 Location: sticksville, ct.
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Posted: Sun Dec 08, 2024 6:19 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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heimlich wrote: |
If you have something pulling too much vacuum changing the distributor won't fix it unless the vacuum canister is the problem.
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you can't have something "pulling too much vacuum" it's fucking impossible
manifold vacuum is 15-22 inHg at idle and the same is true at ported vacuum be it a carburetor or a throttle body
The only way those numbers change is at altitude but that's not a problem here.
Get your original distributer rebuilt. Bill (sparkwerks) is the man for this.
I wouldn't go fiddle fucking with anything until you get that china distributor out of the equation.
Sadly, people think "new is better" and it's just not the case anymore. Please, reach out to Bill. He'll get you dialed in, THEN we can see what you have going on once we get this dialed in to factory specs _________________
gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
Jake Raby wrote: |
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
Brian wrote: |
Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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wcfvw69 Samba Purist

Joined: June 10, 2004 Posts: 13633 Location: Arizona
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Posted: Sun Dec 08, 2024 5:14 pm Post subject: Re: Timing / Idle Questions - 1978 Bay Window T4 2l FI |
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Chris,
As an FYI-
If your bus is going to be a long term keeper for you, consider replacing that Chinese distributor. I've autopsied the Pertronix and most of the other Chinese distributors and to be frank, they are junk like most poorly made VW parts from China.
The original distributors are vastly superior to the Chinese clones. Most of the Chinese distributors I've autopsied were sent in from customers who couldn't get their VW to run right with them. The customers wanted to know what was wrong with them. So, I autopsied them, shared my findings and threw the parts in my metal recycle bin.
I'm not trying to sell you anything but rather, give you and others a heads up.
Cheers- _________________ Contact me at [email protected]
Follow me on instagram @sparxwerksllc
40+ years of VW repair, and VW parts and vehicle restoration experience.
The Samba member since 2004.
**Now rebuilding throttle bodies for VW's and Porsche's**
**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
**Restored Porsche distributors or I can restore yours** |
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