With respect David, that is total bollocksQuote:
Originally Posted by David T
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With respect David, that is total bollocksQuote:
Originally Posted by David T
I am guessing here but I think "total bollocks" loosely translates to "total bullsh-t" in American English. Must be a British saying I assume. Anyway addressing your point, if you disable the idle motor and the Lambda system you can get the PRV to run pretty smoothly, even cold. My point in saying the PRV hunts is that with all of the stock engine systems in place and operating as intended, hunting is normal. The more you open the air screws and bypass the idle motor, the smoother it may run but the idle motor will have less and less control. It needs that control so that when you are running the A/C it can keep the motor from slowing down as the compressor clutch engages. It also helps to prevent stalling as you release the clutch going into first from a stop. Hunting is to be considered "normal" even by the specifications. If you refer to the Workshop Manual, in several places you will find the idle spec to be plus or minus 50 RPM's in recognition of the fact that the motor will hunt normally. It is not that the speed is supposed to be 775 plus-minus, it is that the speed will vary above and below 775 RPM's and still be within spec. I refer you to D:05:02 System Notes #5.Quote:
Originally Posted by MikeWard
The stock idle ECU has no fancy crystal controlled clock and fancy digital logic. The idle speed tolerance would be the tolerance of the idle ECU components and the variable of aging and heat changing those component values.
That's just your interpretation David.Quote:
Originally Posted by David T
Funny that nobody seems to understand what a PID controller does with a dead time.
I learned this an a college in California...any my friend Jordan recognized the dead-time / slow
reaction...
I understand PID control. I tried to explain the control function of the engine control in post no.19 in:Quote:
Originally Posted by Elvis
http://dmctalk.org/showthread.php?15...umpiness/page2
It appears I cannot get to closed loop. I unplugged the WOT and I'm still getting a dwell reading of about 53.8 on the dwell meter (4 cylinder). The RPM ran about 1200 but once I plugged the WOT back in the RPM settled back down to about 800. I unplugged the CO2 and got the same reading. Plugged it back in and got the same reading. The CO2 is new. Perhaps the wire on the CO2 is bad?
You'll get the figure of approx 54 deg if the switch on the wide open throttle is closed OR the lambda temp switch is closed.Quote:
Originally Posted by lazabby
When the coolant temp is above 80 c, the lambda switch will then open (with the wide open switch is open), before the ecu will operate in closed loop mode using the oxygen sensor voltage input as reference, or it will default to 45 deg. The design is that the fuel computer will only operate in closed loop mode once the engine is at this temperature.
You could remove the fuel computer electrical plug and remove pin 7 that will remove the lambda and wot switch inputs to the ecu and then see if you get a varying dwell with a hot engine. OR on a hot engine, disconnect the wot and check to see if you get continuity between pin 7 and pin 5. This will determine if the lambda switch is open or closed. It should be open circuit on a hot engine.
I hope I've explained this ok so far.
Good luck Shannon
I agree you should get the wire disconnected to trouble shoot if it's the temp switch or the lambda ECU bad. Most owners probably won't attempt to remove a pin from the lambda ECU connector (although it's not hard to do with experience). You could also disconnect the wire at the bulkhead connector but those female pins are hard to pull from the connector. Another option is to cut the wire and then join it back when your testing is done.
Since your holding that 54 degree dwell it must be the temp switch or lambda ECU bad.
Nick, please explain - 80°C ?Quote:
Originally Posted by NckT
the manual says 15°C ?!? D:04:10
before 80°C the ecu operates in closed loop mode ?
Sorry I'm confused. What am I gettting wrong ?
@ Shannon - for the O2 sensor to operate it needs 300°C. It then will generate a "high" voltage (1V ?!?) that
will activate the ECU into closed loop mode. Before that - it will stay at the cold / enrich PWM.
This can take a while and sitting in the garage at idle in cold weather - will take a long time.
I've seen that some weeks ago when I measured my lambda ECU and O2 sensor. I was close to replace the
sensor but before that I talked to a friend who is a car genious and runs his own shop. He told me to wait
or drive the car to heat the sensor up above 300°C.
I made a mistake, it is 15 c not 80 c as I said. (That's the last time I try and convert c to Fahrenheit in my head as I got that completely wrong too as it's 59 not 80 ! :)
The o2 sensor will give a sinusoidal voltage signal between 0.2 to 0.8 volts.
I'm working on getting back to this issue. I still have some hunting when I start that smooths out in about a minute or two. I'm still getting a dwell reading of around 54 with little fluctuation. I'm about to borrow someone else's lambda ECU to see it the reading changes.Quote:
Originally Posted by Bitsyncmaster
Is the wire from the CO2 to the lambda ECU suppose to show a voltage? I put a multimeter on the wire where it connects to the wire going directly to the ECU. I didn't read any voltage. I will say that I may not have set the multimeter to the right setting (200ma) or perhaps it was not grounded properly. I also found a small cut in the wire. It looks like a few strands may have been cut. The CO2 sensor is fairly new, replaced last year.
If the lambda switch is closed, the ecu will always default the frequency valve to dwell of 54, regardless of what the O2 sensor signal is, so replacing the ecu with another one is very likely to give you the same result. So try the following test:
.....on a hot engine, disconnect the wot and check to see if you get continuity between pin 7 and pin 5. This will determine if the lambda switch is open or closed. It should be open circuit on a hot engine........
I was looking at the wide open throttle (WOT) microswitch. It has two "plungers" in it. I believe the top one if for the automatic transmission kickdown (my car is auto). The lower one is for the lambda. The lower plunger is pushed in and will not move while the upper one freely moves when depressed. Can the lower one be the problem and is there a way to lubricate it or fix it so that it freely moves?Quote:
Originally Posted by NckT
Possibly. Try the following test:Quote:
Originally Posted by lazabby
.....on a hot engine, disconnect the wot and check to see if you get continuity between pin 7 and pin 5. This will determine if the lambda switch is open or closed. It should be open circuit on a hot engine.....
If you disconnect the wot switch and the dwell operates as normal, you've narrowed it down to the stuck-on wot microswitch. Electrical switch cleaner should help unstick it and clean the contacts.
Trust me ;)
Good luck
If a micro switch is stuck it will stick again. They are not expensive so just replace it. In the meantime just disconnect it and see if you can get into "closed loop" ie, the dwell fluctuates.
I unplugged the microswitch, took the car for a drive to get it warm. When I got back I put a dwell meter on it and it fluctuated normally. It was within normal range so now I know the microswitch needs to be replaced. I still have the hunting when I first start that disappears suddenly in about a minute. Could this be the lambda ECU? I borrowed one to switch out if I need to test this.Quote:
Originally Posted by David T
Shannon, more info, photos and links for those microswitches here: http://dmctalk.org/showthread.php?13...-Switch-Wiring
It is normal for the motor to hunt for a moment when first started and cold.
Nick, You were right. It turned out to be the wide open throttle switch. I unplugged it and go the normal swing on the dwell meter. Turned out it was within normal range. I need to replace the WOT.Quote:
Originally Posted by NckT
I started the car this morning and it still hunts when cold. Need ideas of what to look for.
A few monts ago before I had to replace my injectors the engine did not hunt when cold. The car started right up and had a steady idle.Quote:
Originally Posted by David T
What reading do you get on the dwell on a warm engine now?
You could look into what I put in post No.23 (#23) in:
http://dmctalk.org/showthread.php?15...umpiness/page3
Good luck
Quote:
Originally Posted by NckT
THe dwell is between 35-45.
When the motor first starts, cold, it starts on the cold start valve. It is not exactly metered and is overly rich. Kind of like a choke on a carbureated car. It only squirts while cranking so it stops shooting in fuel quickly but it takes a moment for all of that fuel to be vaporized and consumed. Once consumed the motor has to "get used to" the leaner mixture so it slows down, overshoots, the idle motor overcompensates, the idle shoots up and the idle motor has to again compensate. The pulses dampen out but it takes a few cycles. The idle ECU does not communicate with the Ignition ECU or the Lambda ECU so they all act simultaneously sometimes against each other. Each ECU operates independently but are connected because they all control the same motor but each has it's own function so some functions overlap and some don't. The quality of the idle is very dependent on all of the cylinders working exactly equally. Especially till the motor warms up and the Lambda ECU can get into "Closed Loop".
Bottom line, some hunting when cold is to be considered normal and you do not try to "fix" it.
Video evidence of non hunting when cold is in post No.30Quote:
Originally Posted by NckT
http://dmctalk.org/showthread.php?15...umpiness/page3
Are you absolutely sure you're not making a trip to Houston Texas any time soon? We have nice hot weather, great BBQ, great beer and NASA is not too far away plus Delorean Motor company is in the area. I'm sure we can round up a few cars for you to tinker with. :)Quote:
Originally Posted by NckT
I would love to come over to visit, when I get some time/ funds. I'm definitely sold on Beer and BBQ ;)
I have dwell meter and multimeter. What setting does one use to check the RPM of the engine and where are the probes placed in the engine?
Most RPM meters use the ignition coil (negative side). There are some optical RPM meters but you usually need to add a foil reflector on the pulley.