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 Posted: 07-14-2015 07:32 pm
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answerman

 

Joined: 09-10-2012
Location: Little Chute, Wisconsin USA
Posts: 435
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 Spent quite a bit of time trying to track down Ms. Jenavieve's misfire issue. After doing all of this, it still remains. To recap: she starts, idles, and mostly runs fine under most circumstances, but once warmed up, when accelerating from an idle after a stop, she misfires and backfires once or twice. Then, she's fine till the next stop, and then it happens again. I can not reproduce this at speed (when cruising, I can stomp on the accelerator and she reacts like she should without any misfires). It only happens when accelerating after she's been idling for a few seconds or more.

Here's what I've done so far:

Carbs were balanced at the Jensen East meet courtesy of Ron Mau and Brett Gibson. Didn't seem to affect anything.

Screwed down temperature compensators. No change.

Took distributor out, cleaned it up inside and out, relubricated the wick, inspected points (seemed to be fine). Reinstalled distributor, set timing to about 5 degrees BTDC. Seems to advance fine when blipping the throttle. However, the problem persists.

Properly gapped and installed new NGK plugs. Old plugs looked ok. No change.

Removed timing belt cover, disconnected coil, manually turned engine to TDC. Everything lines up as it should: 110/110 on the cams.

Removed bypass valves, cut and installed full face gasket. No change.

I then removed most of the vacuum hoses, removed the vacuum switch, and capped all ports.  Here's a before and after view, using Mark Rosenbaum's diagram, which I edited a bit for the "after" diagram:

Original routing:



After removal and capping (caps are shown in red, I also capped the vacuum retard port on the distributor which isn't in the diagram):




The only vacuum lines in place now are the canister purge line and then T'd to the carbs (the pink line in the diagram). Obviously, the choke connector is still there as is the dark blue line to the fuel tank. All light blue lines are gone, the vacuum switch is gone, and the line to the distributor vacuum retard line is gone. Caps installed on the front carb throttle bypass port, the two rear carb ports, and the port on the intake manifold that was feeding the green lines to the vacuum switch and the vacuum retard on the distributor. Then, reset the ignition timing to approximately 12 degrees BTDC, reset the idle to about 1000 RPM, and it advances to just over 30 degrees at higher RPMs (I couldn't see the tach and the timing mark at the same time, so I'm guessing I was at about 3000 RPM).

Whew.

Yet, the problem persists. I'm running out of ideas. I really think it's an ignition issue, and my next step was to talk to Mike at Delta about a Pertronix distributor and coil. I know it's a good idea, but I hate to go through the expense and time if it's not going to solve this issue. Anyone?

Last edited on 07-14-2015 07:36 pm by answerman