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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Wed Feb 03, 2021 10:48 pm Post subject: Pulsing at idle/lower RPMs |
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I've got a weird issue with my 1984 1.9 Vanagon.
When the engine gets up to temperature, it will rev the RPMs in a pulsing manner both at idle and when I'm slowing down from a driving speed.
It is an automatic transmission, and it doesn't have this issue if I am stationary but still in gear (such as at a stoplight), and it doesn't occur when I give the van any gas (like when driving/revving the engine at idle). So the engine having a load on it directly affects this issue.
Things to note,
I have replaced the fuel filter, (I'll be checking this and the fuel tomorrow, just in case there is water or something in there)
I replaced the temp 2 sensor.
I replaced the oxygen sensor, but still, have an oxygen sensor light on on the instrument cluster for some reason.
I've replaced the ignition coil, distributor cap, rotor, and sparkplugs/wires.
I also checked for a vacuum leak, but couldn't find any. (I'll probably double check this though)
I also tried a different airflow meter, and the same issue occurs with that one.
The engine also runs pretty rich, and when it's doing the pulsing thing the exhaust smells pretty strongly like there's probably some unburnt fuel in it.
I just checked/adjusted the timing a little, but didn't want to change it too much.
As I retarded the timing, the pulsing seemed to mellow out a bit, but not completely. When I got to the point where the pulsing seemed to mostly go away, it no longer had the correct 35 degrees of advance when "all in", so I adjusted it to what I think *should* be correct timing, and the issue is still present.
I'm having a really hard time figuring out what this issue can be, has anyone had any similar issues?
Could this be an issue with my O2 sensor giving bad feedback to the ECU?
Could it be the fuel injectors?
Could it just be the timing pulleys on my engine aren't correctly lined up, and it needs slightly less advance?
Any insight on this would be greatly appreciated!
Thank you all,
Jimi |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17155 Location: Retired South Florida
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Posted: Thu Feb 04, 2021 5:49 am Post subject: Re: Pulsing at idle/lower RPMs |
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Are the throttle switches connected and working? There is also an adjustment. I say switches because I recall the digijet had one or two depending on generation. The digijet has a digital idle stabilizer mounted next to the coil. You need to disconnect both leads and plug them together when adjusting timing. It controls idle speed by small timing adjustments. _________________ ☮️ |
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markswagen Samba Member
Joined: January 28, 2018 Posts: 1039 Location: san diego
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Posted: Thu Feb 04, 2021 8:21 am Post subject: Re: Pulsing at idle/lower RPMs |
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the OXS light in the dash,
follow the speedometer cable from the wheel to the sway bar, you will find a box the cable goes in one side and out the other to the dash, there's a button on there, push the button, the OSX light should go out, and stay out, for 10k maybe 15k miles, i don't know, i've never bothered to find out.
it's like a service light on a modern car. _________________ markswagen {mobile mechanic} san diego area all early VW's cared for.
619 201 0310 |
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Thu Feb 04, 2021 8:25 am Post subject: Re: Pulsing at idle/lower RPMs |
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MarkWard wrote: |
Are the throttle switches connected and working? There is also an adjustment.
The digijet has a digital idle stabilizer mounted next to the coil. You need to disconnect both leads and plug them together when adjusting timing. It controls idle speed by small timing adjustments. |
I tested the throttle switches with a multimeter per the Bentley. And they seem to be fine.
And I did not disconnect/squeeze the idle stabilizer because I was going off a samba article on timing adjustments, not the Bentley. (They said this was supposed to be the better way to get accurate timing?) I can recheck timing based on what the Bentley says tonight though. (I should have done this in the first place)
Thank you for your help! |
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Thu Feb 04, 2021 8:30 am Post subject: Re: Pulsing at idle/lower RPMs |
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markswagen wrote: |
there's a button on there, push the button, the OSX light should go out, and stay out, for 10k maybe 15k miles, i don't know, i've never bothered to find out.
it's like a service light on a modern car. |
That’s amazing! Thank you for this info! I’ll do that tonight!
-Jimi |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17155 Location: Retired South Florida
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Posted: Thu Feb 04, 2021 9:20 am Post subject: Re: Pulsing at idle/lower RPMs |
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Nothing wrong with timing for total advance. But what you should do is watch the timing mark while the engine is idling. It's likely moving around as it should, but you might see the movement corelate to the surge.
Bypassing it takes it out of the equation completely. You might find the idle improves with it bypassed.
The digijet should have an auxilary air regulator for giving you a faster idle during warm up. It should also have at least on solenoid valve on the firewall by the air cleaner for raising the idle when power steering pressure is at limit. With AC, it will have an identical valve mounted next to it connected to the AC compressor circuit. _________________ ☮️ |
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Thu Feb 11, 2021 10:40 am Post subject: Re: Pulsing at idle/lower RPMs |
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Hello everyone,
Sorry for the delayed update.
I'm realizing now that the reason it does it after it gets up to temp is because the AUX air is working properly and giving it extra RPMs. But once it gets up to temp, it closes off and the issue starts becoming noticeable.
I checked the timing at idle while the engine was doing the pulsing thing, and like MarkWard stated, the pulsing seems to be corelated to timing mark jumping around. But the issue didn't seem to improve when I bypassed the idle stabilizer either.
On another note, I was able to get my OXS light to go off thanks to Markswagen's insight on that!
I also checked the fuel filter, and some of the fuel that was in the fuel tank, and there was a negligible amount of water in the fuel (1/4 teaspoon in ~1.5 liters of fuel).
I'm going to be double checking for vacuum leaks and making sure all my electrical connections are good. Can anyone thing of anything else I should think about testing?
Thank you all,
-Jimi |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17155 Location: Retired South Florida
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Posted: Thu Feb 11, 2021 10:45 am Post subject: Re: Pulsing at idle/lower RPMs |
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There should be zero water. Common water entry points are the fuel tank expansion tanks located in both front fenders. There is a valve on top with a large grommet that fails over time. Water and dirt are thrown up there by the tires where gravity takes over and funnels it back into the fuel tank.
I no longer reseal or replace fuel tanks without dropping both expansion tanks. _________________ ☮️ |
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Thu Feb 11, 2021 11:38 am Post subject: Re: Pulsing at idle/lower RPMs |
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MarkWard wrote: |
There should be zero water. |
To be honest I was worried that there was any in there at all too, but after giving it some thought I think the water came from using a gas can with a funnel while it was pouring down rain. Since then the van has been stored in a garage/never ran while raining.
After taking out what little water there was in there, it is still experiencing the same pulsing issue.
I'll definitely put resealing all the tanks on my soon to do list though!
Thank you,
-Jimi |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17155 Location: Retired South Florida
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Posted: Thu Feb 11, 2021 12:11 pm Post subject: Re: Pulsing at idle/lower RPMs |
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Your engine should have a vacuum advance diaphragm on the distributor. It should have 2 fittings. One is connected to intake vacuum and the other gets vacuum at throttle. These units do fail and leak vacuum. Have you tested them? The inner fitting pulls timing retard and the outer nipple pulls timing advance. _________________ ☮️ |
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oceanair Samba Member
Joined: June 09, 2013 Posts: 720 Location: Victoria, BC
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Posted: Thu Feb 11, 2021 12:26 pm Post subject: Re: Pulsing at idle/lower RPMs |
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Quote: |
I no longer reseal or replace fuel tanks without dropping both expansion tanks. |
Do you replace them with the new metal ones? Or what do you do? _________________ 84 Vanagon Pop Top Conversion from Tin Top, 1970 Ghia - all sweet rides! Love em!
Previous: Green 72 Tin Top, White 72 Westy, Blue 64 Beetle, Yellow 71 Squareback, 2014 Jetta TDI Wagon - wish I could have them all back! |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17155 Location: Retired South Florida
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Posted: Thu Feb 11, 2021 1:14 pm Post subject: Re: Pulsing at idle/lower RPMs |
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I clean the original tanks with soap and water. Reinstall with new grommets. _________________ ☮️ |
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Thu Feb 11, 2021 5:58 pm Post subject: Re: Pulsing at idle/lower RPMs |
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MarkWard wrote: |
Your engine should have a vacuum advance diaphragm on the distributor. It should have 2 fittings. One is connected to intake vacuum and the other gets vacuum at throttle. These units do fail and leak vacuum. Have you tested them? The inner fitting pulls timing retard and the outer nipple pulls timing advance. |
I've wondered about the vacuum on it before. How do I test the fittings? You're talking about the ports directly on the diz right?
-Jimi |
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Howesight Samba Member
Joined: July 02, 2008 Posts: 3274 Location: Vancouver, B.C.
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Posted: Thu Feb 11, 2021 7:10 pm Post subject: Re: Pulsing at idle/lower RPMs |
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You test them with your vacuum pump with a gauge. First ensure that your vacuum pump with gauge is attached to the vacuum canister with a properly-sealing hose. Pump to vacuum. Observe the gauge. It should either hold steady or leak down VERY slowly. The factory vacuum hose can leak a bit, so check that it is not a leaker. If a distributor vacuum actuator is leaking when you test it, you will likely hear a hiss. _________________ '86 Syncro Westy SVX |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32634 Location: Reading Pennsylvania
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Fri Feb 12, 2021 9:07 am Post subject: Re: Pulsing at idle/lower RPMs |
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djkeev wrote: |
Out of curiosity, while your erratic idle is occurring what happens if you remove the oil fill cap? Even just loosen it to break the seal?
Put it back on.......
Now....
What happens if you pinch close the hose from the engine vent tower to the intake?
Dave |
I actually tried the oil fill cap trick already, but unfortunately it did not help the situation at all. I haven't tried pinching the hose from the tower, I can try that next though.
-Jimi |
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JimiD Samba Member
Joined: August 16, 2020 Posts: 42 Location: WA
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Posted: Fri Feb 12, 2021 9:08 am Post subject: Re: Pulsing at idle/lower RPMs |
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Howesight wrote: |
You test them with your vacuum pump with a gauge. |
I'll have to test it out. Thank you
-Jimi |
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16CVs Samba Member
Joined: February 22, 2004 Posts: 4026 Location: Redwood City, California
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Posted: Fri Feb 12, 2021 9:42 am Post subject: Re: Pulsing at idle/lower RPMs |
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Sounds like classic dirty grounds to me. My 1.9 did this to me one time, it was running rich as hell and I tried the throwing parts thing at it and it ran really well after I cleaned the grounds.
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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eeebee Samba Member
Joined: July 17, 2009 Posts: 431 Location: Tujunga
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Posted: Fri Feb 12, 2021 10:26 am Post subject: Re: Pulsing at idle/lower RPMs |
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Bad grounds or connections is a possibility. It probably doesn't happen before it comes to temp because it is running in open loop where it is ignoring the sensor inputs. There is a fuel injection trouble shooting manual i've seen which is a big help. _________________ Eric
1987 Vanagon Wolfsburg Special Edition
GoWesty 2.3
Democracy is the recurrent suspicion that more than half of the people are right more than half of the time. |
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vandam Samba Member
Joined: September 05, 2012 Posts: 116 Location: Oregon
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Posted: Tue Mar 09, 2021 6:44 pm Post subject: Re: Pulsing at idle/lower RPMs |
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https://www.thesamba.com/vw/forum/viewtopic.php?t=570224&highlight=
search air flow jimmy rig if this link doesn't work, my 1984 Vanagon did the same thing and then I adjusted the circuit board so the wiper hit fresh carbon track, fixed my issue, and might be worth looking at. You can see in the photo that it had worn a spot into the board. Good luck
_________________ 84 GL, 2.1 rebuilt |
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