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1950split Samba Member
Joined: December 08, 2005 Posts: 450
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Posted: Sat Mar 23, 2024 11:06 am Post subject: Idle timing increase when engine warms up |
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Hi Everyone!
I have a strange issue.
My 2276 engine with a msd distributor and Mallory Hyfire 6 AL2 is doing strange things
When I start my engine, idle is at 10 degrees btdc at 1000 RPM. But soon after I start driving, idle increases at 1400 rpm, ignition increases to 15 degrees btdc.
I then readjust timing to 10 btdc/1000 rpm, and after a few blips on the gas pedal, I am back to 1400 rpm/15 degrees btdc.
I have torn the distributor apart, cleaned and lubed it. Then I have switched from 48 IDA’s to a set of DRLA’s (as I thought it might be carb related), but nothing changed. I have the same issue whether with a CSP or a Berg linkage.
I also changed my intake gaskets.
What do you think is the issue? I don’t want to drive with such a high idle/15 degrees btdc.
Could a sticky gas cable be the issue? But the Berg has strong return springs so I have some doubt that this is the problem.
Thanks!
Phil
Last edited by 1950split on Sat Mar 23, 2024 1:21 pm; edited 4 times in total |
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clonebug Samba Member
Joined: January 29, 2005 Posts: 4026 Location: NW Washington
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Posted: Sat Mar 23, 2024 11:10 am Post subject: Re: Idle timing increase when engine warms up |
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Check your throttle linkage. Once the engine warms up it might expand and pull the throttle plates open which will then increase rpm and bump the timing up due to rpm increase. _________________
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1950split Samba Member
Joined: December 08, 2005 Posts: 450
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Posted: Sat Mar 23, 2024 11:13 am Post subject: Re: Idle timing increase when engine warms up |
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Hi,
Yes I have set up my linkage (rod lengths) with the engine warm and running in order to monitor if rpm increase when I tighten the Gene Bers rods. |
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Teeroy Samba Member
Joined: April 20, 2003 Posts: 3682 Location: Eastern WA
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Posted: Sat Mar 23, 2024 4:36 pm Post subject: Re: Idle timing increase when engine warms up |
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To eliminate cable causing it, unhook it and see what it does _________________ Pres. Rivercity VW Club www.rcvwclub.org
Founder Derr Wheat Panzers (DWP)
ARR #3
www.autosportsnorthwest.org |
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mikedjames Samba Member
Joined: July 02, 2012 Posts: 2715 Location: Hamble, Hampshire, UK
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Posted: Sun Mar 24, 2024 10:41 am Post subject: Re: Idle timing increase when engine warms up |
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Yes, your engine runs more freely when it is warmed up .
So it climbs up the advance curve on the distributor as they all do, increasing timing and RPM on the way.
A stock bus would set timing at 800-850 rpm , you may do better aiming for a lower idle speed, with your 10 degrees timing advance. In a stock distributor, 1000 rpm is about where idle timing starts to climb from the plateau below 1000 rpm.
I can get my EDIS based ignition on my 1641 to idle at 600 rpm with 10 degrees advance, I have programmed in a timing "valley" around 850 rpm, with timing advancing both sides of the valley. I prefer it at 850 rpm though.
In fact I have watched it pick up and idle from 500 rpm.. _________________ 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.
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Millionmph Samba Member
Joined: November 22, 2021 Posts: 283
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Posted: Sun Mar 24, 2024 4:00 pm Post subject: Re: Idle timing increase when engine warms up |
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Read the title, and nobody mentioned the obvious yet, vaccuum leak when warmed up.... |
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1950split Samba Member
Joined: December 08, 2005 Posts: 450
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Posted: Mon Mar 25, 2024 9:24 am Post subject: Re: Idle timing increase when engine warms up |
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When I have been adjusting my carbs in the past, I have been able to adjust idle speed by rotating the distributor.
In the present situation it has no impact, I rotate the distributor but almost instantly idle goes from 1000rpm to 1500rpm.
Vacuum leak, not at the manifold gasket level.
I’ll recheck my valve play , I guess that perhaps a play that is too tight with a warm engine could cause this.
Ultimately I’ll do a leak down test. That will at least help me to find which cylinder is guilty |
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Zed999 Samba Member
Joined: March 04, 2018 Posts: 1240 Location: UK
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Posted: Mon Mar 25, 2024 9:46 am Post subject: Re: Idle timing increase when engine warms up |
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I think you have your timing set just on the point the advance kicks in. When it does, the engine revs higher so the advance is maintained, which keeps the revs up.
If your distributor is adjustable in a way that delays the advance kicking in I'd try that. Otherwise back off the idle timing a degree or two. |
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Millionmph Samba Member
Joined: November 22, 2021 Posts: 283
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Posted: Mon Mar 25, 2024 12:23 pm Post subject: Re: Idle timing increase when engine warms up |
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If you got heavier spings toss those in, maybe your advance springs are too light |
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heimlich VWNOS.com
Joined: November 20, 2016 Posts: 6554 Location: Houston, Texas
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Posted: Mon Mar 25, 2024 5:21 pm Post subject: Re: Idle timing increase when engine warms up |
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RPM and advance are directly correlated.
Are you saying that you are at idle and 10 degrees than wait 5 minutes and it goes to 15 and then you adjust it back down to 10 and 5 minutes later it goes back to 15? _________________ www.vwnos.com [email protected]
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VW_Jimbo Samba Member
Joined: May 22, 2016 Posts: 9879 Location: Huntington Beach, CA
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Posted: Mon Mar 25, 2024 10:16 pm Post subject: Re: Idle timing increase when engine warms up |
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Millionmph wrote: |
Read the title, and nobody mentioned the obvious yet, vaccuum leak when warmed up.... |
This was my first thought, after I read the title. Or the wrong vacum signal (manifold) the distributor (should be ported).
But really depends on how it was set up. _________________ Jimbo
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1950split Samba Member
Joined: December 08, 2005 Posts: 450
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Posted: Tue Mar 26, 2024 6:18 am Post subject: Re: Idle timing increase when engine warms up |
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Hi Heimlich,
Yes that’s exactly what I mean.
What is weird is that it started doing this while I was on a longer drive.
At the beginning of the drive everything was fine and it suddenly started acting this way. I’lll try to back-off my idle speed screws a little but I am pretty confident that the throttle plates are nearly shut currently. |
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heimlich VWNOS.com
Joined: November 20, 2016 Posts: 6554 Location: Houston, Texas
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Posted: Tue Mar 26, 2024 6:23 am Post subject: Re: Idle timing increase when engine warms up |
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1950split wrote: |
Hi Heimlich,
Yes that’s exactly what I mean.
What is weird is that it started doing this while I was on a longer drive.
At the beginning of the drive everything was fine and it suddenly started acting this way. I’lll try to back-off my idle speed screws a little but I am pretty confident that the throttle plates are nearly shut currently. |
Sounds like the distributor is turning in the clamp. Take a marker or something similar and put a line on the shaft and put that same line on the clamp. Drive it until you see the issue and see if it moved. _________________ 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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Glenn Mr. 010
Joined: December 25, 2001 Posts: 76761 Location: Sneaking up behind you
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Posted: Tue Mar 26, 2024 6:42 am Post subject: Re: Idle timing increase when engine warms up |
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heimlich wrote: |
1950split wrote: |
Hi Heimlich,
Yes that’s exactly what I mean.
What is weird is that it started doing this while I was on a longer drive.
At the beginning of the drive everything was fine and it suddenly started acting this way. I’lll try to back-off my idle speed screws a little but I am pretty confident that the throttle plates are nearly shut currently. |
Sounds like the distributor is turning in the clamp. Take a marker or something similar and put a line on the shaft and put that same line on the clamp. Drive it until you see the issue and see if it moved. |
Some aftermarket clamps are soft and the entire clamp twists, so the mark won't move because the engine clamp is moving. _________________ Glenn
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heimlich VWNOS.com
Joined: November 20, 2016 Posts: 6554 Location: Houston, Texas
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Posted: Tue Mar 26, 2024 6:46 am Post subject: Re: Idle timing increase when engine warms up |
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Glenn wrote: |
heimlich wrote: |
1950split wrote: |
Hi Heimlich,
Yes that’s exactly what I mean.
What is weird is that it started doing this while I was on a longer drive.
At the beginning of the drive everything was fine and it suddenly started acting this way. I’lll try to back-off my idle speed screws a little but I am pretty confident that the throttle plates are nearly shut currently. |
Sounds like the distributor is turning in the clamp. Take a marker or something similar and put a line on the shaft and put that same line on the clamp. Drive it until you see the issue and see if it moved. |
Some aftermarket clamps are soft and the entire clamp twists, so the mark won't move because the engine clamp is moving. |
The same scribe method will work. Continue the scribe down to and include the engine case. _________________ 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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Glenn Mr. 010
Joined: December 25, 2001 Posts: 76761 Location: Sneaking up behind you
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Posted: Tue Mar 26, 2024 7:00 am Post subject: Re: Idle timing increase when engine warms up |
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heimlich wrote: |
Glenn wrote: |
heimlich wrote: |
1950split wrote: |
Hi Heimlich,
Yes that’s exactly what I mean.
What is weird is that it started doing this while I was on a longer drive.
At the beginning of the drive everything was fine and it suddenly started acting this way. I’lll try to back-off my idle speed screws a little but I am pretty confident that the throttle plates are nearly shut currently. |
Sounds like the distributor is turning in the clamp. Take a marker or something similar and put a line on the shaft and put that same line on the clamp. Drive it until you see the issue and see if it moved. |
Some aftermarket clamps are soft and the entire clamp twists, so the mark won't move because the engine clamp is moving. |
The same scribe method will work. Continue the scribe down to and include the engine case. |
Ok, that will work. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
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rayjay Samba Member
Joined: March 26, 2008 Posts: 1501 Location: Buford GA
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Posted: Tue Mar 26, 2024 8:12 am Post subject: Re: Idle timing increase when engine warms up |
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What springs and advance limiting bushing are you running in the MSD distributor? When I recurved distributors for a living I always set them up so the advance didn't start to kick in for 200 to 300 rpm above idle speed. If the advance is kicking in at or slightly above idle speed you will have an inconsistent idle. |
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