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pfewesty Samba Member
Joined: October 29, 2020 Posts: 6 Location: South Carolina / Maine
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Posted: Wed Jan 13, 2021 4:46 pm Post subject: 90 Vanagon suddenly running rough - coil? |
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I'm new here - 1st post is a ramble. Until recently my relatively new to me 1990 Westy with 165k miles has been running beautifully since I got it about 2 months ago. I've put 3.5k miles on it. I was returning from a 100mi. trip and driving up an incline on a bridge when the engine started to miss and it felt like a cylinder was dropping out. When the road flattened out it ran better, but would miss every now and then for the remainder of the drive. This problem has gotten progressively worse over the last 2 weeks with the engine missing under acceleration/load. Van always starts instantly. Pulled plugs. 1&2 looked good. 3&4 somewhat fouled but not too bad. While running I pulled wires off the distributor. #3 seemed to be the problem. Swapped plug wires between 3 and 4. Problem seemed to follow the wire. Installed new plug wires. Engine started right up as usual and ran well until warm -- 2-3 minutes -- then started to miss. I pulled plug wires again and now I can't reliably find the problem cylinder. It seems to move. Injectors are good. Could this be a coil issue? In my 35 yrs. of wrenching on cars I've only replaced a coil once or twice. |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32625 Location: Reading Pennsylvania
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pfewesty Samba Member
Joined: October 29, 2020 Posts: 6 Location: South Carolina / Maine
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Posted: Wed Jan 13, 2021 5:21 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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Thank you for the quick reply. Yes -- AMC heads installed by PO in 2018. I have the paperwork somewhere so I can see which shop in Seattle did the work which might inform the quality of valve work. I forgot to mention that I put more oil into this engine than anything I've ever owned. Maybe a 1/2 qt. to qt. per visit to the gas pump. Not a visible leak anywhere. Westy friends tell me "not to worry -- oil is cheap". |
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DanHoug Samba Member
Joined: December 05, 2016 Posts: 4790 Location: Bemidji, MN
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Posted: Wed Jan 13, 2021 5:47 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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not to bash AMC but i lost an exhaust valve guide within 10k miles on super duper modified GoWesty head. point being, it happens, not bashing GW nor AMC but somewhere along the line setup or materials were wrong.
i think tight factory valve guide clearance was my failure foil... it was interesting to set up my own head and establish valve guide clearance by the spec... it felt sorta loose to me but allows the all important oil-of-life to get to the rubby bits.
or your coil could be bad. or the O2 sensor. or the TempII sensor. or the fool pump. or the regulator. or your Blummenvasen is empty. _________________ -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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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17153 Location: Retired South Florida
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Posted: Wed Jan 13, 2021 6:19 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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VW felt a qt of oil in 1000 miles was acceptable. Maybe pull the sparkplugs again and do a compression test. Easy to install new plugs at the same time. Then see how it does. _________________ ☮️ |
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pathao Samba Member
Joined: November 01, 2012 Posts: 291 Location: Montreal, Canada
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Posted: Wed Jan 13, 2021 6:48 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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pfewesty wrote: |
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Engine started right up as usual and ran well until warm -- 2-3 minutes -- then started to miss.
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Try unplugging O2 sensor and see if that has any effect _________________ 1982 AC P27 - 2.0 FI FED - 091 - BA6
English is a second language to me |
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pfewesty Samba Member
Joined: October 29, 2020 Posts: 6 Location: South Carolina / Maine
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Posted: Thu Jan 14, 2021 8:01 am Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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This AM --Started right up and drove nice for 5mins. or so. Just as the temp mark was moving out of the white it started missing. Disconnected o2 sensor from green wire and it smoothed out within a couple of seconds. Runs and drives good (maybe not great) with wire disconnected. Green wire (all wires for that matter) to ECU is as from factory and unmolested. Service records from PO indicate new o2 sensor installed in 2018. Failed sensor or ground/short in wire?
Thank you all. Happy to have eliminated head problems for now! |
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Ahwahnee Samba Member
Joined: June 05, 2010 Posts: 9810 Location: Mt Lemmon, AZ
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Posted: Thu Jan 14, 2021 8:17 am Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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pfewesty wrote: |
...I put more oil into this engine than anything I've ever owned. Maybe a 1/2 qt. to qt. per visit to the gas pump. Not a visible leak anywhere. Westy friends tell me "not to worry -- oil is cheap". |
How full are you filling the oil?
Many (e.g. me) find things do better if the oil level is about 1/3 of the way up from the bottom mark.
It is easy to overfill -- because of the angle of the stick there is not a huge difference between the two marks. |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17153 Location: Retired South Florida
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Posted: Thu Jan 14, 2021 8:30 am Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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The oxygen sensor is polling all 4 cylinders and to a point will adjust for any straying of the stock mixture. This works great when all 4 cylinders are running equally.
When the sensor can create a problem is when one or two cylinders are not running to spec. Say you have one lean cylinder. The average mixture to the sensor is lean. It sends a message to the ECU to richen the mixture. The ECU can only adjust pulse width for all 4 equally. So, its adding fuel to all the cylinders when only one is really needing more fuel.
When you disconnect the oxygen sensor, this tug of war ends. The engine is actually running in open loop off of it's preprogrammed fuel map.
So, yes your sensor could be bad, but it could also be that the engine is out of spec for what the sensor is wanting, and that's why the engine runs better with the sensor disconnected.
In theory, a proper running in tune engine should not need the oxygen sensor at all and mpg performance etc would be equal to running in closed loop. _________________ ☮️ |
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pfewesty Samba Member
Joined: October 29, 2020 Posts: 6 Location: South Carolina / Maine
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Posted: Thu Jan 14, 2021 8:55 am Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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I try to keep the oil level just above the bottom mark. |
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hdenter Samba Member
Joined: October 14, 2008 Posts: 2754 Location: San Luis Obispo, CA
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Posted: Thu Jan 14, 2021 9:39 am Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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Have you checked for any exhaust leaks? Even a minor leak upstream from the O2 will draw in air and fool the O2 sensor into thinking you are running lean...
Hans _________________ '79 triple white convertible bug
'84 sunroof vanagon
'85 weekender |
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16CVs Samba Member
Joined: February 22, 2004 Posts: 4025 Location: Redwood City, California
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Posted: Thu Jan 14, 2021 10:44 am Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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Mine had the same issue, turned out to be a bad Vacuum line coming form the intake to the Power brake line. You could nit really see it until you removed it and then it was painfully obvious. The metal support wires were rusting and it just ate through the line.
I chased this for a while and changed out a few parts along the way. It now runs better than it has for years.
Stacy _________________ 1987 Syncro Westfalia Triple knob (bastard)
1989 Syncro Tristar Triple knob "Swedish"
2013 Jetta Hybrid a true "Zwitter"
Samba member # 14980
Call anytime number 650 722 4914 .
Keep Your van running and upkept tastefully for the love of the hobby.
Don't let your van end up in an "abortions" thread. |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50349
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Posted: Thu Jan 14, 2021 1:50 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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Dump a bottle of FI into the fuel tank and see if that clears things up. |
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pfewesty Samba Member
Joined: October 29, 2020 Posts: 6 Location: South Carolina / Maine
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Posted: Thu Jan 14, 2021 6:08 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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I'll check/do and report back. Thank you. |
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22668 Location: NYC/Upstate/ROW
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Posted: Thu Jan 14, 2021 7:42 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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Stop driving it.
New plugs, cap , rotor, wires. Check all grounds fir the engine fir bright and shiny connections. Careful inspection of the Hallsensor wiring on the distributor
A new to you car needs evaluation of fuel tank quality, fuel line replacement, clamp replacement. _________________ .ssS! |
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pfewesty Samba Member
Joined: October 29, 2020 Posts: 6 Location: South Carolina / Maine
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Posted: Tue Jan 19, 2021 6:06 pm Post subject: Re: 90 Vanagon suddenly running rough - coil? |
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I put in new plugs, wires, checked and cleaned cap and rotor, grounds, wiring and reset the timing. I pulled the o2 sensor, found it to be very sooty and replaced it with a new one. everything seems to be back to normal and it is running well again. so between running rich and likely some oil blow through it seems the o2 sensor was contaminated -- |
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