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borninabus Samba R&D Dept.
Joined: May 18, 2006 Posts: 4539 Location: Arizona Highways
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Posted: Mon Jun 18, 2012 2:48 pm Post subject: |
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what kind of exhaust do you have & how rusty is it? _________________ 88 Van WBX, A/T - 13 JSW TDI 6M/T - 2012 Touareg TDI Sport |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jun 18, 2012 3:03 pm Post subject: |
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dabble wrote: |
Hi guys - I am having a problem with my 78 2.0 FI:
I replaced the plugs, wires, cap, and rotor. I set my idle at 1k rpm, and my timing is in spec at 7.5*btdc and 28* btdc 3500rpm.
My problem is this:
I have a sputter/pop/backfire when I let off of the accelerator. It does not make this sound when I am on the throttle. It does not sputter/pop/backfire as much when I am stationary and press the throttle. The sound goes away immediately when I depress the clutch.
I've checked for vacuum leaks and I can't find any. Thoughts? Decel valve need to be replaced?
Thanks! |
air getting into exhaust or bad decel or loose vacuum hose / broken tee. |
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dabble Samba Member
Joined: April 21, 2004 Posts: 271 Location: Olympia, Wa
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Posted: Mon Jun 18, 2012 3:18 pm Post subject: |
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SGKent wrote: |
dabble wrote: |
Hi guys - I am having a problem with my 78 2.0 FI:
I replaced the plugs, wires, cap, and rotor. I set my idle at 1k rpm, and my timing is in spec at 7.5*btdc and 28* btdc 3500rpm.
My problem is this:
I have a sputter/pop/backfire when I let off of the accelerator. It does not make this sound when I am on the throttle. It does not sputter/pop/backfire as much when I am stationary and press the throttle. The sound goes away immediately when I depress the clutch.
I've checked for vacuum leaks and I can't find any. Thoughts? Decel valve need to be replaced?
Thanks! |
air getting into exhaust or bad decel or loose vacuum hose / broken tee. |
I just replaced the exhaust with a new one - no leaks there. I'll check again for vacuum leaks. I bought some carb cleaner so I can try that tonight.
Is it weird that it only does it when the bus is actually moving? Any way to test the decel valve? _________________ 1973 Westy with a 78 FI 2000cc
[url=http://www.vw-mplate.com/mplate2-9157.png]Click to view image[/URL] |
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babysnakes Samba Member
Joined: August 19, 2008 Posts: 7108
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Posted: Mon Jun 18, 2012 5:00 pm Post subject: |
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In the Bentley, FI section, p24.Disconnect decel valve wire from atf pressure switch, ground disonnected wire to clean metal and listen for a click at valve. No click-bad valve. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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dabble Samba Member
Joined: April 21, 2004 Posts: 271 Location: Olympia, Wa
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Posted: Wed Jun 20, 2012 10:59 am Post subject: |
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My bus is a 73 with a 78 2.0. GE is the engine code (I think...).
My vacuum hoses don't look the same as the one in the ratwell picture, but I'll check to make sure they're all connected and not leaking.
Does anyone sell a replacement kit for vacuum hoses? Or should I just try to piece together new hoses? _________________ 1973 Westy with a 78 FI 2000cc
[url=http://www.vw-mplate.com/mplate2-9157.png]Click to view image[/URL] |
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Randy in Maine Samba Member
Joined: August 03, 2003 Posts: 34890 Location: The Beach
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Posted: Wed Jun 20, 2012 11:13 am Post subject: |
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Post a picutre of your engine set up. Also what is the number on that distriburtor you are running? |
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Westfabulous Samba Member
Joined: January 07, 2007 Posts: 4207 Location: The tropic of Canada, dodging the giant flying moose of Surrey!
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Posted: Wed Jun 20, 2012 11:36 am Post subject: |
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dabble wrote: |
My bus is a 73 with a 78 2.0. GE is the engine code (I think...).
My vacuum hoses don't look the same as the one in the ratwell picture |
Do you have an automatic? That would be one reason why the hoses are different. _________________ *****************
"I will gladly pay you Tuesday for a hamburger today." |
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Stuartzickefoose Samba Post Whore
Joined: February 07, 2008 Posts: 10350 Location: SoCal for now...
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Posted: Thu Jun 21, 2012 4:36 pm Post subject: |
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What is the proper technique for setting the AFM at a rough placement as far as the adjustment for enriching and leaning out the mixture? and how should it be set in relation to the throttle body idle adjustment screw?
1978 FI 2.0
see sig line _________________ Stuart Zickefoose
2011 Jetta Sportwagen TDi 6 speed manual
206-841-7324
[email protected] |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Thu Jun 21, 2012 4:48 pm Post subject: |
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Stuartzickefoose wrote: |
What is the proper technique for setting the AFM at a rough placement as far as the adjustment for enriching and leaning out the mixture? and how should it be set in relation to the throttle body idle adjustment screw?
1978 FI 2.0
see sig line |
don't go there without an air to fuel meter to test with. It is like shooting bullets without being able to see where the target is or where the bullets are going. Colin has one, let him drop by. |
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Stuartzickefoose Samba Post Whore
Joined: February 07, 2008 Posts: 10350 Location: SoCal for now...
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Posted: Thu Jun 21, 2012 5:01 pm Post subject: |
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SGKent wrote: |
Stuartzickefoose wrote: |
What is the proper technique for setting the AFM at a rough placement as far as the adjustment for enriching and leaning out the mixture? and how should it be set in relation to the throttle body idle adjustment screw?
1978 FI 2.0
see sig line |
don't go there without an air to fuel meter to test with. It is like shooting bullets without being able to see where the target is or where the bullets are going. Colin has one, let him drop by. |
i have access to one, and was going to tune it properly there, but how should i set it to get it close? 3 turns out, or something? _________________ Stuart Zickefoose
2011 Jetta Sportwagen TDi 6 speed manual
206-841-7324
[email protected] |
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tootype2crazy Samba Member
Joined: October 08, 2007 Posts: 1276 Location: St. Louis Missouri
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Posted: Mon Jun 25, 2012 6:30 am Post subject: |
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I have been running FI for about 7 months now and it has been great. The problem I have been having is between 2000 - 3000 rpm it runs rough and pops in the exhaust will revving it. It has a tiny flat spot upon acceleration as well. It has great power overall, though. Especially above 3000 rpm its great.
I suspected the AAR, I took it out adjusted and tested it and it is ok. I also suspected a vacuum leak so I checked every single connection yesterday, taking it all apart and putting it back together, no change. I also thought it might be the coil and distributor cap and rotor. A while back while turning the distributor to adjust the timing the cap came loose while the engine was running, destroying the cap, rotor, and coil. I put a used set on that I had in the basement from and old engine. Is it possible that those parts are causing this? The problem has gotten progressively worse from over the last few months, seemingly from the time I put the ignition components on, although I can't be sure of that.
I also checked and greased all the electrical connections yesterday. It did seem to give it a little more pep, but did not change the rough running between 2000-3000 rpm.
Is there something I'm overlooking or that I should test? I have been through the troubleshooting in the L-Jet manual but I just can't pinpoint anything. _________________ air-cooled or nothing for me
1978 Sunroof Deluxe Bus (daily driver)
1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's) |
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dabble Samba Member
Joined: April 21, 2004 Posts: 271 Location: Olympia, Wa
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Posted: Mon Jun 25, 2012 9:15 am Post subject: |
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Went camping this weekend...
Made it 30 miles to work on Friday with no problems - just some intermittent popping/backfiring.
Put in a full day of work on Friday and started the next 60 mile leg of the trip to Anacortes. More consistent popping/backfiring, loss of power, and felt like the engine was missing. Still made it to Anacortes running and mostly happy.
I re-did the timing and checked all of my ignition and vacuum connections on Saturday before embarking home on Sunday.
Trip home on Sunday had much more backfiring and loss of power. Stopped and re-did timing and checked hoses - couldn't see any problems. One thing I noticed was that my vacuum advance was not working when revving the engine up to 3500 rpm.
Driving home and the bus dies on I-5. It starts and runs, but dies when I let off of the accelerator. I checked for vacuum leaks and couldn't find any, timing is set at static because I can't rev it up to 3500 rpm without it dying.
Towed it home and I'm at a loss. Help? Suggestions on a shop to take it to in Seattle? _________________ 1973 Westy with a 78 FI 2000cc
[url=http://www.vw-mplate.com/mplate2-9157.png]Click to view image[/URL] |
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Stuartzickefoose Samba Post Whore
Joined: February 07, 2008 Posts: 10350 Location: SoCal for now...
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Posted: Mon Jun 25, 2012 10:59 am Post subject: |
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start with the vacuum advance problem...not good _________________ Stuart Zickefoose
2011 Jetta Sportwagen TDi 6 speed manual
206-841-7324
[email protected] |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jun 25, 2012 11:07 am Post subject: |
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tootype2crazy wrote: |
I have been running FI for about 7 months now and it has been great. The problem I have been having is between 2000 - 3000 rpm it runs rough and pops in the exhaust will revving it. It has a tiny flat spot upon acceleration as well. It has great power overall, though. Especially above 3000 rpm its great.
I suspected the AAR, I took it out adjusted and tested it and it is ok. I also suspected a vacuum leak so I checked every single connection yesterday, taking it all apart and putting it back together, no change. I also thought it might be the coil and distributor cap and rotor. A while back while turning the distributor to adjust the timing the cap came loose while the engine was running, destroying the cap, rotor, and coil. I put a used set on that I had in the basement from and old engine. Is it possible that those parts are causing this? The problem has gotten progressively worse from over the last few months, seemingly from the time I put the ignition components on, although I can't be sure of that.
I also checked and greased all the electrical connections yesterday. It did seem to give it a little more pep, but did not change the rough running between 2000-3000 rpm.
Is there something I'm overlooking or that I should test? I have been through the troubleshooting in the L-Jet manual but I just can't pinpoint anything. |
Have you put your timing light on it to see if the timing is bouncing all over the place at in that range or cutting out - it needs to be rock steady.
If that is Ok you may have a worn spot on the AFM. Do you know how to look for that? |
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tootype2crazy Samba Member
Joined: October 08, 2007 Posts: 1276 Location: St. Louis Missouri
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Posted: Mon Jun 25, 2012 11:20 am Post subject: |
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SGKent wrote: |
Have you put your timing light on it to see if the timing is bouncing all over the place at in that range or cutting out - it needs to be rock steady.
If that is Ok you may have a worn spot on the AFM. Do you know how to look for that? |
I'll do the timing light thing and see how that goes. I do not know what a worn AFM looks like, although I was thinking that could be it since it only runs bad in a certain rpm range, i. e. the most used one. Can you point me to the right direction for checking that out? _________________ air-cooled or nothing for me
1978 Sunroof Deluxe Bus (daily driver)
1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's) |
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Stuartzickefoose Samba Post Whore
Joined: February 07, 2008 Posts: 10350 Location: SoCal for now...
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Posted: Mon Jun 25, 2012 11:52 am Post subject: |
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tootype2crazy wrote: |
SGKent wrote: |
Have you put your timing light on it to see if the timing is bouncing all over the place at in that range or cutting out - it needs to be rock steady.
If that is Ok you may have a worn spot on the AFM. Do you know how to look for that? |
I'll do the timing light thing and see how that goes. I do not know what a worn AFM looks like, although I was thinking that could be it since it only runs bad in a certain rpm range, i. e. the most used one. Can you point me to the right direction for checking that out? |
take a knife and cut the seal on the top of the AFM (black plastic flat piece) off, and see if the area the arm moves across is worn in any place. (Someone back this up...im not the best at this) _________________ Stuart Zickefoose
2011 Jetta Sportwagen TDi 6 speed manual
206-841-7324
[email protected] |
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tootype2crazy Samba Member
Joined: October 08, 2007 Posts: 1276 Location: St. Louis Missouri
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jun 25, 2012 12:28 pm Post subject: |
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the red RTV shows that someone has been in there before. Regular RTV has acids in it that cause corrosion in electronic parts. I see some lines in the circuit board although it does not look bad. If the timing is steady and the stumble goes away above 3000 RPM then it could be anything from a wire wiggling to a bad AFM. You can get some electronic contact cleaner from Fry's or Radio shack and spray a tiny bit on the board to see if it gets better.
Were it me I would start with a full tune up including plugs, valve adjust, compression test etc. It could also be a valve or valve seat floating. |
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tootype2crazy Samba Member
Joined: October 08, 2007 Posts: 1276 Location: St. Louis Missouri
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Posted: Mon Jun 25, 2012 1:00 pm Post subject: |
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Just a quick question: what should the normal vacuum be? I have a mighty vac with a gauge on it and would like to see if I'm pulling the correct vacuum. Also I would read this on the plenum, right?
The system I bought was used so I'm betting the previous owner of it was having similar problems. I might just spring for a rebuilt AFM to be sure. _________________ air-cooled or nothing for me
1978 Sunroof Deluxe Bus (daily driver)
1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's)
Last edited by tootype2crazy on Mon Jun 25, 2012 1:07 pm; edited 1 time in total |
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