[DML] Running Problem-Rich Mixture (Long)

["dukeofclassiccars" <tswatch@xxxxxxxx>]

Hi List,

First, thanks to everyone for their help to get my car up and 
running.  I would say that I've seen it all after what I've been 
through, but new/weird things keep showing up.

I only have one last problem to fix (an oxygen 
sensor/idling/hunting/CO problem ? I'll get more into this
later).  I could drive the car now the way she is, but something is 
not right about the way she runs.

Let me start off by saying that I do not have any vacuum leaks (to 
the best of my knowledge - 99% sure).  Let's at least assume that 
there are no vacuum leaks.  This seems to be everyone's first 
response, if not at least one of their responses.

My car runs well.  She starts and holds an idle about 950.  I can't 
say that she is really running smooth, but she is not running badly.  
Let's start off with the history of the car... She sat for five 
years; Need I say more.  I took her into my home and adopted her.  
Fortunately, I had extra funds for her to consume.  (She didn't even 
run when I bought her, but the price was right.)  Now she starts, 
runs, and moves well.  The acceleration doesn't even seem to be 
affected by my problem.  I've replaced tons of parts; all have
tested bad.  I've seen everything from bad parts to bad wires. 
I've
even seen wires going to the wrong place (which resulted in a lot of 
swearing at the car).

I believe that all my parts in the lambda/idle system are working 
properly now (except the oxygen sensor; it is working, but not as it 
should be).  I have a wiring problem with my idle speed switch and 
vacuum advance, but they are currently hooked up (as the manual 
shows) temporarily by the use of jumpers.  My throttle plates are 
fully shut with no additional play or binding in the linkage.

My problem? she CAN run smoother once the oxygen sensor kicks in 
(after it `hunts' for a little bit), but she must be `in
the mood' in order to run the way I want her to.  I've
temporarily 
made an adjustment to the idling system.  I know this bothers many 
DeLorean owners, but it is what works for now to solve my problem.  I 
have replaced the idle speed motor with a manual valve, which allows 
me to adjust the air-flow without playing with the so-called 
brass "Forbidden Screws".  I originally had a problem with
the idle speed motor.  It wants to stay open all the way, even after 
replacing all the bad parts (except the ECU, which is the next step) 
and checking all the wires in the idle speed system (yes, I do 
believe there are no vacuum leaks).  I got her to run nicely by 
playing with the manual valve and disconnecting the oxygen sensor.  
She now idles around 950 RPM.

My oxygen sensor and lambda system is what's driving me nuts. 
After locating a bad ground on pin four of the lambda ECU and 
replacing the oxygen sensor, I finally got her to run the way she 
should be.  I start my car and use my manual valve to set the idle - 
no problems (except for the slight rich fuel mixture).  Then I give 
her some time to warm-up so the oxygen sensor kicks in.  Once the 
sensor kicks in, she hunts for a minute (varying up and down in 
speed) and then stays at the higher speed that sounds great!  Her 
idle jumps up to about 1400 RPM.  By using the manual valve, I can 
cut her idle back down to 950 RPM (this is with the valve all the way 
closed).  I assume that once I get my idle speed motor working 
correctly, it should do the same and cut back on the air-flow.

Problem solved!  I just need to cut the air back manually EVERYTIME 
when I want to drive her!  I could just fix my idle speed motor 
problem (which I'm really trying to avoid because I'm trying
to find a way to work around it so I will never have to use it).  
What about my oxygen sensor?  Well, it always reads at 1.8 volts (and 
it should be at 0.5 - 0.7 volts).  I can't figure out the answer
to 
this one yet (and I know it is simple, I just think my mind is fried 
from working on everything else on the car).  If it has a higher 
voltage than it should, does that mean it is getting too much oxygen, 
or too little?  I played with my CO adjustment screw and my air 
valve; nothing would change my reading on the oxygen sensor.  My only 
guess is that I have another bad wire somewhere (or ground).

As before, I said that I can now drive her; and I can do that 
successfully without adjusting the manual air valve.  I just unplug 
my oxygen sensor - no problem.  She runs a bit rich at 950 RPM, but 
not horrible (she doesn't try to die on me).  I don't think
driving her like this for short distances would hurt the engine at 
all, at least from what I see.  I do not plan on keeping her like 
this, but she really just needs to run after sitting a long time.

I have one last thought regarding the fuel distributor/pressure 
regulator.  I have receipts, from the previous owner, showing that a 
new fuel distributor was bought from a DeLorean vendor.  I'm
aware that you cannot just keep buying parts and expect the car to 
run better.  I haven't seen any postings regarding this issue,
but, I
was reading in the workshop manual learned that the pressure 
regulator could be adjusted.  If I increase the regulated pressure, 
would that let more fuel in or less fuel in?  If I could reduce the 
amount of fuel that goes into to engine without affecting the air 
(and I wouldn't need to cut back on the fuel that much), then I
think 
I could get my oxygen sensor to read the correct voltage.

If you read my problem this far, thanks very much, I know there is a 
lot.  I'm trying to list everything so you know my problem.  If
you 
have any input as to my problem, please send your information my way.

~Dan
VIN# 3817 ? Born again.





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