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ClassicCamper Samba Member
Joined: December 17, 2002 Posts: 679
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Posted: Sat Oct 24, 2015 1:08 pm Post subject: Popping, Surging and Stalling - Solved! |
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73 D-Jet overhaul ran good for about 650 miles. Now car surges at cruising speeds, stalls at idle. After a long ride on highway you can hear the engine popping or backfiring upon acceleration, causing it to surge. Im pretty sure the popping is occuring in the plenum.
Heres whats been done:
- timing (at 3500 RPM and idle)
- valves adj
- checked all grounds and vac hoses
- fuel pressure ok
- all new FI components and harness (exc ECU)
- points seem ok
- plugs, cap, wires, etc new
It just started doing this out of the blue after running fine. Im stumped.
Last edited by ClassicCamper on Thu Oct 29, 2015 9:29 am; edited 1 time in total |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21474 Location: Oklahoma City
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Posted: Sat Oct 24, 2015 3:37 pm Post subject: |
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There is onoy one thing that causes popping into the plenum...and that is either a burned valve, sticking valve or grossly poorly adjusted valves.....I am doubting its popping into the plenum.
Other items are primarily ignition related....shorting plug wires.....or sticking breaker plate.
The surging sounds primarily like fuel restriction or a vacuum leak opening up at high rpm. That can include the MPS. This can be caused by the TB o-ring. This can be caused by a serious vacuum leak anywhere in the oil dipstick system of thd wagon.
This will not be caused by either of the other two sensors in the EFI.
This is most commonly caused by fuel pressure fluctuation meaning the opening of the fuel inlet in the tank alt Dr nately getting clogged and unclogged by silt. Is there still a sock filter in the tank?
Or the fuel pump losing prime and cavitating for any number of reasons.....old pump....power fluctuations. .....kinked hose.....plugged filter. Ray |
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ClassicCamper Samba Member
Joined: December 17, 2002 Posts: 679
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Posted: Thu Oct 29, 2015 9:28 am Post subject: |
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Thanks Ray, I found the problem. The lobed distributor shaft that the points ride on had some kind of varnish on it. Despite dabbing a little grease on the shaft, the hard plastic piece that rides along it wore down (again) and the points actually remained closed.
I didn't catch this b/c I just installed the points. I never had this happen on an ACVW before, but always a first time. I cleaned the varnish off of the distributor shaft and put a tiny dab of grease on the rider. There is no more squeak from the engine now; car runs great.
Sometimes its just the simple things! Thanks again. |
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Lars S Samba Member
Joined: October 04, 2007 Posts: 780 Location: Sweden
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Posted: Thu Oct 29, 2015 11:18 am Post subject: |
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Glad you found it!
Also glad you reported back - we all learn from each other.
Lars S _________________ Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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