85 GW AMC 360 rough idle w heavy exhaust

[Bentley]

Hey gurus, I’m at a total loss and hoping you might have some insight.

85 GW, AMC 360, Motorcraft 2100 carb, Motorcraft distributor w TFI upgrade and MSD 6a ignition module

The GW has been a high school daily driver for my kids for years with no major issues until a few months ago. After driving in town for 10-15min, it would simply stall out and not re-start for anywhere for 30min to 1 day. As time wore on, it would die (without any hesitation or stuttering) sooner and sooner, and it took longer and longer for successful re-start until it’s finally would no longer restart.

I initially started by replacing the mechanical fuel pump, but then turned my attention to the ignition, and since I had planned for the TFI upgrade anyway, I figured now is the time to do it.

Replaced:
Coil
Larger cap & rotor
Plugs & wires
Ignition switch
Starter relay solenoid
Ignition mod swapped for MSD 6a

At this point, the intermittent spark continued and the old battery was giving up, so replaced the battery and had the starter checked to confirm all was in order. During the instances when it would actually start, it ran much more smoothly than it ever has before, but inevitably it would suddenly die as before. After checking/re-checking my wiring and grounds and scouring the forum discussions, I found a forum comment that was confirmed by the tech support at MSD that suggested the magnetic pickup might be the issue for the intermittent spark signal.

Since I was reusing the distributor, I marked the rotation of the distributor base relative to the block, and the rotor relative to the cap before pulling the dist to swap the mag pickup. When I reinstalled the distributor after swapping the pick up, it wouldn’t seat so that my prior rotational marks lined up exactly. I didn’t have a helper to assist in confirming Top Dead Center, but I was anxious to see if the new pick up made a difference, so I turned the key, and the starter would barely turn over. I decided to stop until I had a helper before moving forward.

The next day, I pulled the distributor and #1 plug, and while rotating the crank by hand and using a wooden dowel in the #1 plug hole, found TSD. That rotation also matched up the timing mark on the harmonic balancer for TSD. Reinstalled the distributor, and wouldn’t you know, the rotor matched up with the number one plug wire, and the base was back to its (+/-) original rotation.

Turned the key, and it fired right up, but stuttering a bit and blowing heavy smoke from the exhaust….something it’s never down before. Rotating the dist a bit smoothed the rough idle somewhat, but it still has massive hesitation upon pressing the accelerator.

So pulled the 2100 Motorcraft carb and confirmed the power valve and accelerator pump were still good. Also swapped the PCV valve that I found was clogged full of oil/gunk.

Still starts on the first crank, but with a bit of rough idle, bogs down/hesitates significantly upon acceleration (almost like it wants to backfire)…and blowing smoke

It started running rough only after the dist/mag pickup removal/re-install sequence. There also is now a loud hissing sound coming from the passenger rear of the engine.

The antifreeze in the radiator looks pristine, but the oil on the dipstick smells of fuel.

Thank you in advance for any ideas or directions you might have!

Sam

[NAL5376]

Sounds like a leaking power valve in the carb and a vac leak to go with it.

[tgreese]

Good suggestion. However, you are replying to a duplicate post - viewtopic.php?p=227317#p227317