Re: need frequency valve help

["John Hervey" <dherv10@xxxx>]

Walter, This is the second try to get this to you thru the Group. 
Others that don't know about how the circut works may want to know 
also. ( No tools required ). Checking the Lambda. DMCJOE said a while 
back that in all his years of working on De Loreans he has only had 
one that he could remember bad unit. I have been sent 3 to check out 
so far and none were bad. ( If it's bad i can repair it.)
Maby the FQV is working all the time and that's why you can't tell 
when it's not working. ( I tell by listening and by feel ) I have 
done this forever with most of the older cars. They will tell you by 
listening what's wrong. There are three things that operate the 
Lambda unit. #1: Oxygen sensor. #2.Thermal Switch. #3.Full throttle 
switch.
First thing to do heat the car up to normal operating temp. Then 
reach under the throttle cover ( Black ) if you have one and press in 
the full throttle switch. Lean over and listen for the FQV to buzz if 
it isn't already. If you hear it buzz for a second or two then the 
Lambda unit is getting power and the 02 sensor and thermal switch are 
not stuck closed. 02 sensor ( Very important ) if contaminted due to 
chemical additives, bad gas or just old, it could keep the FQV 
operating all the time also. Unplug it and listen to the FQV. Then 
check the thermal switch. When the car is cold, the Lambda unit sends 
out a signal to the FQV to run untill the 02 sensor can heat up and 
start adjusting the air/gas ratio. I change 02 sensors on all my cars 
by what the book say. 30,000 mi on unheated and 60,000 to 100,000 on 
heated.All this is provided there is no contamination.
Hope this helps
John Hervey

w--- In dmcnews@xxxxxxxxxxx, "Walter" <Whalt@xxxx> wrote:
> I've had an on-going cold acceleration problem in my Delorean and 
haven't
> had much luck getting advice on how to fix it. Maybe someone on 
this list
> can help?
> 
> So far I have tried unplugging the electrical connection to my 
frequency
> valve, and it makes absolutely no difference to how the engine runs.
> 
> The engine coughs, sputters, pops, and runs rough until it 
completely warms
> up. When I force the engine to run richer by pulling a vacuum on 
the
> delayed side of the control pressure regulator, then the engine 
runs fine!
> I have checked the fuel pressures and they are within specs.
> 
> My question to the group is: How can I tell if my frequency valve 
is
> working? I've tried unplugging it and this makes no difference. 
I've tried
> unplugging the Lambda ECU and this makes no difference either. 
I've put a
> volt meter across the wires going to the frequency valve and measure
> nothing. I realize that a volt meter is probably the wrong tool 
for this,
> but I don't have access to an oscilloscope. Is there some other 
diagnostic
> tool that is appropriate here? I could check for flow with a fuel 
pressure
> gauge, but I hate to take those connections apart if I don't need 
to. I do
> get continuity through the coil, but that won't help if nothing is 
going to
> it.
> 
> For those of you who like to read, here is an earlier message I 
wrote to the
> DML that never got posted. It explains more of my symptoms:
> 
> What can cause a Delorean to hesitate during acceleration, but 
forcing the
> control pressure regulator to make it run richer cures the 
problem? I've
> checked the fuel pressures, and they are all normal. I get primary 
pressure
> of 5.1 bar. The control pressure regulator gives 2.9 bar with cold 
engine,
> 3.7 bar with fully warmed up engine.
> 
> Pulling a vacuum on the delay side of the control pressure 
regulator drops
> the fuel pressure under 2 bar and cures all my problems. But, the 
fuel
> pressure isn't supposed to be that low. So is this compensating 
for some
> other problem? And if so, what is it?
> 
> At idle, my vacuum reading is 15 inHg, but it jitters +/- 2.5 
inHg. Is this
> normal? My vacuum at 2000 rpm is 17 inHg and smoothes out. Is 
this a
> symptom of a stuck valve or is this normal?
> 
> This problem has been intermittent in the past and would only 
happen to a
> cold engine. Now it happens all the time, and it doesn't really 
matter if
> the engine is cold any more. Now even after the engine is warmed 
up, I get
> hesitation, coughing, sputtering and even backfiring.
> 
> When I start the engine, it tends to stall. Any pressure on the 
accelerator
> makes the engine hesitate, cough, sputter and pop. When I release 
the
> accelerator, the engine speed actually picks up for an instant and 
then
> drops back to a rough idle. This keeps up until the engine is 
hot. Before
> I drive the car, I have to let it warm up for at least 5 minutes. 
After the
> engine is fully warmed up and I turn it off and let it sit for 30 
minutes, I
> have to let it warm up all over again before I can drive it.
> 
> Walt Tampa, FL