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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50334
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 Posted: Wed Sep 22, 2021 10:15 am Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| TomInAlaska wrote: |
| Abscate wrote: |
| Waiting on the coil replacement. Ignition wires age, history too? |
Wires are these: https://www.napaonline.com/en/p/BEL700344?impressionRank=3
and have less than 20 miles on them. Plugs are NGK 1263s and were replaced at the same time. (new cap and rotor, too) |
When I bought my 87 Syncro it had brand new aftermarket wires on it that all checked out fine ohm wise. But the engine just ran like crap. I pretty much switched every part of the FI and ignition system out using the parts from my '91 excepting the new spark plug wires with no success. When I finally swapped the wires the engine purred. Don't know what was wrong with them but apparently something in the ECU didn't like them. |
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Wed Sep 22, 2021 10:18 am Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| Wildthings wrote: |
When I bought my 87 Syncro it had brand new aftermarket wires on it that all checked out fine ohm wise. But the engine just ran like crap. I pretty much switched every part of the FI and ignition system out using the parts from my '91 excepting the new spark plug wires with no success. When I finally swapped the wires the engine purred. Don't know what was wrong with them but apparently something in the ECU didn't like them. |
I still have the old wires that still seem to be in good condition. Maybe I'll swap those back on to see if there's any change.
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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jlrftype7
Samba Member
Joined: July 24, 2018
Posts: 3576
Location: Chicago
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| Posted: Wed Sep 22, 2021 10:39 am Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| TomInAlaska wrote: |
| Wildthings wrote: |
When I bought my 87 Syncro it had brand new aftermarket wires on it that all checked out fine ohm wise. But the engine just ran like crap. I pretty much switched every part of the FI and ignition system out using the parts from my '91 excepting the new spark plug wires with no success. When I finally swapped the wires the engine purred. Don't know what was wrong with them but apparently something in the ECU didn't like them. |
I still have the old wires that still seem to be in good condition. Maybe I'll swap those back on to see if there's any change. |
Good idea since without the benefit of a Scope on the Secondary Ignition System for testing your spark pattern, coil, etc-, figuring out weird running issues under a load can be frustrating
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto |
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Fri Sep 24, 2021 6:40 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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New coil came and is installed. It has also been snowing/raining/slushing all day, so I haven't really had a chance to run the engine or especially drive it. Hopefully the roads will be ok for a test run tomorrow since I don't have studded tires on it yet. #alaskaproblems
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 3:06 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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New coil made zero difference. the miss at 2800rpm is still there and happens every time the engine tries to rev through it.
At this point the things that I haven't replaced or proven to myself to be good are the distributor itself, the throttle body, the ECU, and the fuel pressure regulator. What should I throw money at next? Also, how is a complete distributor with a new Hall unit only $80 when just the new Hall unit is $165 
Though I am consoled by the fact that everything I've replaced is very old and needed replacing if this thing is going to be reliable, I'm rapidly reaching the point where I don't want to spend more money on this engine cause I intend to swap in something else at some point (leaning toward an EJ25). In the mean time though, I want to be able to drive it without the stupid miss/hesitation. Grrrrrr
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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djkeev
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Joined: September 30, 2007
Posts: 32574
Location: Reading Pennsylvania
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 3:23 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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I've only got one green wire on the "-" post of the coil and it looks like it goes straight to the ignition control module (which is aftermarket Echlin but age unknown) and the engine doesn't run with that one unplugged, but I did unplug the other wire on the "-" post that feeds directly to the aftermarket tach a previous owner installed. That actually seemed to help: the miss was only there some of the time and at what sounded like the same rpm, so
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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TomInAlaska
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Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 3:25 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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And yes its missing while stationary. I'm currently just testing it in the driveway.
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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DanHoug
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Joined: December 05, 2016
Posts: 4769
Location: Bemidji, MN
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| Posted: Sat Sep 25, 2021 3:35 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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i would remove that capacitor on your AFM for two reasons... the non-soldered wires can setup strange make/break connections with engine resonance at specific RPMs and cause signals the ECU can't interpret. secondly, it almost looks like a ceramic cap, not a tantalum, but that is probably the photo angle. either way, remove it and test.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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TomInAlaska
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Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 3:36 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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So here's a question: should you be able to continuously suck air through the vacuum can on the side of the distributor?
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 3:37 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| DanHoug wrote: |
| i would remove that capacitor on your AFM for two reasons... the non-soldered wires can setup strange make/break connections with engine resonance at specific RPMs and cause signals the ECU can't interpret. secondly, it almost looks like a ceramic cap, not a tantalum, but that is probably the photo angle. either way, remove it and test. |
I actually soldered it in place before resealing the AFM box, but I can definitely pull it out and get a proper one. *adds one of those to the shopping list*
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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djkeev
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Joined: September 30, 2007
Posts: 32574
Location: Reading Pennsylvania
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 3:40 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| djkeev wrote: |
| TomInAlaska wrote: |
| So here's a question: should you be able to continuously suck air through the vacuum can on the side of the distributor? |
No |
AHA!
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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DanHoug
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Posts: 4769
Location: Bemidji, MN
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| Posted: Sat Sep 25, 2021 3:45 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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that's a vacuum diaphragm and should hold suction with zero bleeding. nada. you should also be able to observe the mechanism inside the dist move when suction is applied, tho on a 1.9 dist i'm not positive you'll see this with the Hall window covering things.
_________________
-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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TomInAlaska
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Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 5:21 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| DanHoug wrote: |
| that's a vacuum diaphragm and should hold suction with zero bleeding. nada. you should also be able to observe the mechanism inside the dist move when suction is applied, tho on a 1.9 dist i'm not positive you'll see this with the Hall window covering things. |
I can actually hear air escaping past the diaphragm when blowing by mouth into the advance hose (the one connected to the throttle body) but other side seems to be holding pressure/vacuum and sounds like its actuating the retard mechanism when pulling vacuum by mouth on that hose. In any case, given the age of the rest of the distributor and Hall unit, I just ordered a complete new distributor from Bus Depot. Hopefully that clears this whole issue up for good. <fingers crossed>
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50334
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| Posted: Sat Sep 25, 2021 5:53 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| TomInAlaska wrote: |
| DanHoug wrote: |
| that's a vacuum diaphragm and should hold suction with zero bleeding. nada. you should also be able to observe the mechanism inside the dist move when suction is applied, tho on a 1.9 dist i'm not positive you'll see this with the Hall window covering things. |
I can actually hear air escaping past the diaphragm when blowing by mouth into the advance hose (the one connected to the throttle body) but other side seems to be holding pressure/vacuum and sounds like its actuating the retard mechanism when pulling vacuum by mouth on that hose. In any case, given the age of the rest of the distributor and Hall unit, I just ordered a complete new distributor from Bus Depot. Hopefully that clears this whole issue up for good. <fingers crossed> |
The larger sized nipple which points towards the distributor body is the retard function and the smaller sized nipple which points away from the body is the advance function. The advance can needs to be attached to ported vacuum (no vacuum when the throttle plate is fully closed). If the retard can is bad which is likely, you can just remove the hose from the can and plug it off. But after doing so you will not be able to set the timing by the book but should set it at 28° BTDC at 3800+ rpms, with any hoses removed and plugged. |
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TomInAlaska
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Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Sep 25, 2021 6:20 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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| Wildthings wrote: |
The larger sized nipple which points towards the distributor body is the retard function and the smaller sized nipple which points away from the body is the advance function. The advance can needs to be attached to ported vacuum (no vacuum when the throttle plate is fully closed). If the retard can is bad which is likely, you can just remove the hose from the can and plug it off. But after doing so you will not be able to set the timing by the book but should set it at 28° BTDC at 3800+ rpms, with any hoses removed and plugged. |
Gotcha, so it is the retard diaphragm thats bad. Bentley didn't do a great job of labeling which side is which (at least that I could see). I plugged it off at the distributor end for now and will set the timing as you recommend before driving it while I wait for the new distributor to get here. Thanks
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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TomInAlaska
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Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Fri Oct 01, 2021 4:45 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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Turns out the remanufactured distributor I ordered is actually backordered for the foreseeable future due to material and labor shortages so that got canceled. COVID: the gift that keeps on giving! 
I did find a good used distributor from another vendor that is (hopefully) on the way. While I was in the mood for spending money, I also ordered a set of GW's new injectors and their new throttle body. Gonna have everything but long block replaced soon.
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Tue Nov 09, 2021 3:06 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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I finally drove the van a little today and despite all the things I've done recently including a good used distributor, new GW throttle body, new GW purple injectors, and adjusting the valves, it still has the same hard stumble/miss/whatever at 2800-3000 rpm. 
I think my next step will be to borrow and try out a known good AFM and ECU.
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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TomInAlaska
Samba Member
Joined: June 02, 2007
Posts: 386
Location: Anchorage, Ak
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| Posted: Sat Nov 13, 2021 5:17 pm Post subject: Re: 1.9L engine miss at 2800 rpm? |
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An update: I finally got around to borrowing a known good ECU and with no other changes, the engine ran smoother overall and revved through 3k with zero stumble or hesitation.
So, in my case at least, the skip at 2800 rpm is definitely caused by something inside the ECU.
_________________
'73 Super Beetle (resto-mod/rally look, 1776)
'84 GL adventure van project (1.9L, 4speed) https://www.thesamba.com/vw/forum/viewtopic.php?t=755844&highlight= |
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