77 Bay window 2.0FI hiccups between 3000 - 3800rpm

[heiko910]

[aeromech]

And remove the gas cap🤠
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[heiko910]

Hey Tram,
I hope you took my slight onset of sarcasm with a pinch of humor. No malicious intend on my end. I was just trying to pull you leg.
Peace

[heiko910]

[Tram]

[musktchup]

Ive been reading your thread and does the motor hiccup while you rev it to 3,000+ rpm while sitting in the driveway? If not I agree with your assessment of a fuel line issue, possibly coming from the tank to the fuel filter. You could take an air hose and blow back on it from the upstream filter connection. Then go for a test drive to assess.
If it hiccups while sitting in the driveway revving to 3,000+ rpm I would lean toward something else ignition related as the fuel demand is much less in this state of running.
my .02
Cheers

[heiko910]

[heiko910]

[heiko910]

https://youtu.be/IjPwkFapKaw

Check this out.
I changed to the oem coil and a stock rotor. Set the mixture again and drove it again. No change. I drained the tank, blew through the line into the tank. No change.
Vacuum is good, 17 inch Hg right at the vacuum advance hook up. Timing is set and steady at rpm. 28° with mechanical advance and 39° with vacuum advance.
Tomorrow I will try points.

Anyone any other ideas?

[timvw7476]

great vid , hope the points & condenser will solve this for you.
Best advice about these buses is found at gowest.com. Titled:
Running Issues: Which Injection or Ignition Part On My Vanagon
Is Causing the Problem? Excellent write up by Lucas over there.

[udidwht]

Under load would suggest to me that it's starving for fuel (lean condition). You need to get your hands on a wideband and install a bung and go for a drive.

What fuel regulator you using?
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[mikewire]

Watched your video, nice! You have a good set of diag tools to work with. I think we can rule out your ignition setup.

I may be wrong on this, but your fuel pressure you stated being variable between 29-36psi. When I've tested mine, it was a steady 38psi, so your readings seem low to me. However, I didn't test mine while driving or under load.

That may indicate a FPR, (maybe a vac leak in the line, or failing unit), or a blockage or restriction somewhere. There's the fuel tank, sock filter in the outlet, and since you changed the pump and filter, you may also consider changing the main fuel lines up to the drivers injector rail - it's cheap, will rule out any issues there, and should be done on the regular anyway.

OH one other thing I thought about is your S boot - I had to replace mine recently because it was cracked all over and was giving me similar issues.
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@countdowngarage
@bigskyeuro

1972 VW Kombi 9 Passenger Deluxe w/ 2.0L F.I. VWAC swap
1965 VW Beetle Deluxe Bahama Blue

[heiko910]

[heiko910]

[SGKent]

[SGKent]

one other item. I would guess this is an FI tank - meaning two nipples on it. Once in a great while someone shows up with a single outlet tank in a FI bay, and a tee to recirculate the fuel. When that happens we have seen situations where the fuel aerates and causes weird issues. On a FI Bay, the fuel tank also stores the heat that is generated when the fuel goes thru the fuel pump and engine bay. That way the fuel is always cool when it enters the engine bay.
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[heiko910]

[heiko910]

Today I check the bus for vacuum leaks with my home made smoke generator.
I made a video to show what I did and what I found.
I am going for a test drive to confirm my finding/ potential fix.. Enjoy the video.

https://youtu.be/AhKo7kPm3YA

[SGKent]

throttle shaft leakage is hard to get rid of because the gasket is no longer made although there are substitutes. A member here Phil (whip618) does rebuild them like new. That said I don't think that leak is enough to cause a the stumble. Next I would try it with points and a regular condenser to see if that changes anything. If not next I would try another AFM and see if the spots it stumbles at change.

Good Luck

SK
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[heiko910]