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121 Posts
Discussion Starter #1
At cold start, even in warm weather, the car can act sluggishly including 'meh' start and initial rev, then lackadaisical acceleration, thump in shift 1st to 2nd, hesitations, and idle somewhat low. No improvement during a run--although sometimes it seems to 'pop' back to peak performance (?).

So, drive in city traffic for say 30 to 45 min. Car acts 'tired' entire time. Park and shut down.

Restart an hour later and starts great with nice quick initial rev, then drives with zip, proper shifts, fine response and handling, braking seems better, headlights brighter.

Recently I replaced the very old factory alternator as it had a leaky diode. Seemed to do it. But then the intermittent sluggish thing came back days later.

Is this remaining problem a weak battery--draining quickly when car is shut down for the night or parked for the day, then a good charge from the alt making everything normal again? Or a battery too 'small' for the Vulcan?

Questioning too if the warm start means a vacuum leak has sealed itself. But why the 'pop back' to better overall performance?

I'm thinking there's some faulty electrical component that draws down the battery during lengthy shutdown; or a loose electrical connection that robs power, then reconnects and restores performance. Bad ignition wire? They're only two years old.

No codes or CEL coming on. No battery light coming on. I'm going to try a one-by-one parasitic draw test, though.

BTW, what is that small alternator connector? It seems not to fit well--can wiggle it like a loose tooth. Thanks for any help!

121 Posts
Discussion Starter #2
Two finds today related to this.

  1. Disconnected -ve battery cable. I used my multimeter on 10A configuration and connected leads to -ve battery terminal and -ve cable. Should read almost zero amps. It read 0.45. Then it flipped to 0.22. Then back to 0.45. Then 0.22. I started pulling fuses at the power box. When I pulled fuse #1, the 40A 'Junction Block', the meter went to 0.02. Does this mean the 0.45/0.22 amp draw is downstream in the cabin fuse box? I plan to check that next but have to block shut the door switch. Something is drawing significant amps with the car shut down, though. What's the function of the 'Junction Block'?
  2. I read about MAF sensor troubles causing performance issues. Start engine then disconnect the MAF. Engine should sputter and quit. My engine kept running, rather sputtery, but kept running. So this could mean air is getting in somewhere; or the MAF sensor itself is bad--either dirty or faulty.
After that I used my jumper wire from battery +ve to -ve cable to wipe PCM, reconnected all after a time, turned ignition ON three times for 30s each, than started fourth time, let run to temp, and shut down. Came back 2 hours later and started up, drove off to get CRC MAF and connector spray cleaners, and car performed effortlessly. Smooth shifts and lots of power.

I replaced the nasty old alternator recently because I got a new one at a good price. I checked to see if the P-brake was dragging the rear brakes, but the wheels were barely warm to the touch. Never a CEL since I changed out EGR and DPFE summer 2018.

Something is problematic electrically and that battery could be overtaxed. I understand the MAF sensor is not prone to failure, too, so I'll clean it. If that doesn't work, where could air be getting in that would cause the 'on-off' nature to this sluggishness problem? Maybe it's a temperamental fuel pump? Front O2 sensor and/or wiring? I'll clean that O2 connector, too.

121 Posts
Discussion Starter #3
In case it helps anyone: after I cleaned the O2 sensor connector I got a P1151 O2 bank 2 lean code. The sensor was original Ford green connector. Replaced, code gone, but car still slugged.

Had mechanic test fuel pressure too--it's within spec. Had vacuum lines tested too. No leaks.

Next I replaced that little loose-tooth stator plug atop the alternator.

Ripped out the crummy NGK wires so highly recommended to me in 2018. I found a Standard premium set and the sluggishness ALMOST went away once they were in.

I had the exhaust checked and whaddaya know--a leak at the top of the flex pipe farting warm exhaust. My mechanic found a couple more small leaks; fixed those.

Next, I went after that VSS sensor. Working by feel I found its connector. Old Ford licorice plastic meant a tab almost cracked off, but also that connector came off WAY too easily. I applied some electrical cleaner to the connector and let it dry. The VSS itself was grimy with a wet black residue all over the connector lip, so I got some electrical cleaner in there too. Then I sprayed the connector until dripping out cleaner. Once dry I put a zip tie around the connector body and secured it with electrical tape. The connector SNAPPED loudly into place--it really did feel loose when I first pulled it.

I also saw my PCV valve had a really soft loose rubber cap where the unused elbow should be plugged solid. How did that happen? Valve was ok but replaced it.

Car was really doing well by this point--but still the occasional bumpy sluggy 1-2 shift.

LAST: that vacuum line from oil cap to engine air accordion. The rubber was subtly falling apart at air end while the oil cap end was barely holding to the fitting. Other than that, it looked fine! I got a Motorcraft pipe with solid rubber ends...


New alternator+new stator plug
Ignition wires replaced
O2 sensor replaced
+ve batt cable and power cable replaced (upgrade to bigger AWG +ve and -ve)
Exhaust flex tube replaced
PCV valve replaced
VSS electrical connection cleaned
Oil breather vacuum tube replaced

I made the mistake of using an aftermarket IAC so going to a JY to pull two and try them after cleaning them. I can feel that lazy IAC because the engine is so responsive now!

Anyway, if you have the problem of sluggishness and thumpy 1-2 shifts, that's my report on how I solved mine.
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