Cold acceleration problem

["Walter" <Whalt@xxxx>]

This problem is intermittent. One day it runs fine, the next day it won't
accelerate while cold. Any attempt at acceleration is futile until the
engine is warm. Instead the engine idles rough and coughs, sputters and
pops when I press the accelerator. Then the engine won't run well until it
is fully warmed up. If the engine cools for even 30 minutes, the problem
returns.

Here's what I found so far:

When I disconnect the vacuum line connecting the Thermal Vacuum Control
Valve to the Control Pressure Regulator and draw a vacuum on the delayed
side of the Control Pressure Regulator (simulating loss of vacuum due to
acceleration) then the engine runs fine! This indicates that the engine was
running too lean.

When the engine stalls and is restarted, it runs fine for a few seconds.
(Enrichment from cold start valve indicates engine was running too lean
again.)

When the engine is completely cold, the Thermal Vacuum Control Valve opens
to the Control Pressure Regulator and closes to the distributor advance like
it should. (A hand vacuum pump/gauge confirms this.)

After running for two minutes from being completely cold, the Thermal Vacuum
Control Valve closes to the Control Pressure Regulator and opens to the
distributor advance. Is this too soon?

When I have a vacuum gauge/pump tapped into the vacuum line connecting the
Thermal Vacuum Control Valve to the Control Pressure Regulator, drawing a
vacuum does nothing (as it should). Giving the line pressure (while
pinching off the line to the Thermal Vacuum Control Valve) simulates a
vacuum loss due to acceleration. This gives a fuel enrichment spike
allowing normal acceleration for the duration that the spike lasts --
indicating again that the engine is running too lean.

So, is my Thermal Vacuum Control Valve closing too soon and/or not giving
enough vacuum to operate the Acceleration Enrichment Circuit long enough
and/or strong enough? During the short duration that the valve is open, I
get a continuously fluctuating/vibrating vacuum reading of between 19 to 17
in Hg. Is this normal for the reading to bounce so violently? And is 18 in
Hg proper for a Delorean vacuum?

I have tested my Control Pressure Regulator Delay Valve according to D:02:01
step 7 of the Workshop Manual. What should take 10 seconds +/- 2 seconds
instead takes only 3 seconds. So it appears that the Delay Valve is bad,
but if it isn't getting any vacuum in the first place, then it isn't going
to be of much use. Pulling a vacuum in the reverse direction bleeds down
immediately. So am I testing it right?

I don't think the problem could be in the ECU or oxygen sensor because I
have this lean condition even when the Lambda Thermal Switch is above 15C
(59F) and the oxygen sensor is below 300C and therefore not warmed up yet
anyway. If the fuel circulation from the Frequency Valve back to the tank
is restricted then this could cause a lean condition as well. Is this
likely?

Is my problem somewhere else other than the Acceleration Enrichment Circuit?
Such as a vacuum leak elsewhere in the engine?

This is really an annoying problem. Can anyone offer any suggestions?

Help!
Walt Tampa, FL