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