One for those who remember CFI

I've got a problem with my 84 Mark VII, 302 CFI, that has had me scratching my head for quite some time. After 9 minutes from a cold start (Within 30 seconds either way,I've timed
it!)each and every time I drive it on my commute to or from work, the engine will stumble, miss, hesitate and lose power for 2-3 minutes and then run perfectly from then on. I've never been able to duplicate the concern in the driveway or on a road test with equipment at hand for testing. There are no Continuous Memory codes set and none show up on the KOEO or KOER. I've wiggle tested the wiring under the hood numerous times. The fuel pressure at the TB is fine when tested, although I've never tested the pumps individually.
The problem first surfaced last December at about 108K miles. In February I pulled the engine to reseal it, mainly due to a leaking rear crankshaft seal and rusted oil pan. It got the full treatment along with all of the engine gaskets and pan: Plugs, wires, cap, rotor, pickup coil,TFI, oil pump, water pump,all filters, hoses, belts, O2 sensor, ACT sensor, ECT sensor, TPS, EVP sensor, cleaned the EGR spacer, and installed an EGR filter in place of the cooler. Most of this was done "because I was there" as most parts were original and long overdue for replacement. I didn't want any surprises a week later. You know, those "Damn, I should have..." moments I thought sure that after all of this the problem would be gone. Nope. The maiden voyage after reassembly was a 300 mile round trip. 2 cold starts and the problem occurred at 9 minutes into each then disappeared until the next time. It's showing 132K on the odometer now, and the problem still happens like it has since day one. Any thoughts would be welcome.
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Tom Adkins wrote:

IAC valve. You can also pull engine codes, whether a light comes on or not.
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Sharon K. Cooke wrote:

There's no IAC on a CFI equipped motor. It's throttle body injected and there is no electronic idle control, except for fuel mixture at idle. Later CFI cars used an Idle Speed Control stepper motor. The problem occurs at cruising speed, usually above 35-40 mph. I never noticed it below those speeds, but I'm usually on the highway when it happens. I've attempted to "pull the codes", but there are no codes to pull. I just realized that I've overlooked testing the coil. It doesn't "feel" like a spark concern, but I'm running out of ideas.
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Sounds like EGR. Check the EGR control solenoid. From the '83 service manual:
Disconnect the vacuum line at the EGR valve and connect a vacuum gauge to the hose. Take the engine to 2000-2500 RPM and release the throttle, repeat 8-10 times and check for consistent response.
Hot engine: Vacuum should rise above 15 inches Hg and return to zero when the throttle is released. If the vacuum doesn't return to zero or is inconsistent, the solenoids are worn and should be replaced.
Cold engine: If vacuum rises above zero the solenoids are leaking and should be replaced.
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.

I'd tee a gauge into the EGR vacuum line and connect a gauge to monitor EGR vacuum at the onset of the problem..
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Rick wrote:

necessarily when the problem occurs. I've been out of town during the week for the past few weeks. I'll tape a vacuum gauge to the windshield and tee it into the EGR line and see if I can reproduce the problem while I'm home this weekend. I really don't suspect the EGR because I only (so far)get the symptoms at highway speeds, under load or cruise. If the EGR was opening too much when not needed, I don't think it would be as evident then. (I will check it though, stranger things have happened and I've been wrong before). It feels like an intermittant loss of fuel or spark causing the motor to lose power and miss while trying to accelerate or hold a constant speed. The maddening part is that it will happen only once during a drive cycle, as far as I can confirm. The time constant of the onset (excatly 9 minutes) is making me wonder about the possibility of an exhaust valve sticking open midway through warmup. I know I'm reaching, but...
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