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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Hello. today i pluged in my old scanner. and was wondering can someone make any sence out of this for me .
i dont think i can read it right. anything out of spec. anything wrong? any input?
PROM ID - identifies your memory chip installed
Coolant in degrees centigrade = 100*C (which is = 212*F)
Miles per hour = 0
Manifold pressure V/10 = 39 which is 3.9 volts
Knock Retard in degrees = 2 (your timing is retarded 2* due to knock)
Throttle V/10 = 0.4volts or 400millivolts is the throttle position sensor output
Oxygen reading from your O2 sensor x10mV = 660mV (where 450mV is considered 14.7 air/fuel and stoichiometric)
Mixture Dwell 48 - sorry i would have to google that myself but it looks like related to the fuel injector pulse width
Revolutions per minute X10 = 73 = 730rpm
Barometric pressure V/10 = 46 = 4.6volts (is the sensor output in volts)
ALDL count 141 (is the assembly line data link count what ever that does but the ALDL is your interface connector)
Battery V/10 = 133 = 13.3volts
EGR duty cycle = 58 = 58% of time its open
Closed loop means the ECM is running in closed loop and the O2 sensor is controlling mixture (air/fuel)
XM clutch off (whatever the XM clutch is)
Park/Neutral (means car is in park or neutral)
CAN/ILC ON - where CAN is the controller area network and the ILC is the idle load compensation and are in service
Exhaust Gas Recirculation = OFF (which doesnt make sense with the previous 58% open duty cycle)
Air Injection Reaction Switch is OFF
Air Injection Reaction Div on
Barometric readings in Volts divided by 10
Mixture dwell = the proportion of the time the metering rods are commanded to the lean position. Not sure what the units are. But with the O2 mV at 660, it's running WAAAAYYYYYYY rich. OTOH that ECM's ALDL data rate is like 90 baud or something; it redefines the concept of "slow" in 2015, so it would take averaging a large number of those over considerable time to make sure it's not some kind of temporary spike. Probably took about 2 seconds to download and output the data on that printout there. Maybe longer. This is DEFINITELY NOT a 0411.
XM = transmission (TCC)
This system pre-dates the invention of CAN (Controller Area Network) by around 20 years. CAN/ILC isn't related to that. Can't recall what that is. I'd have to stir up some brain cells that haven't fired since last century and I'm too lazy for that right now. As they say, memory is the second thing you lose as you get old; but I forgot what the first was supposed to be.
I doubt its running rich. The ECM has the integrator or short term fuel trim chase the 14.7 stoiciometric air fuel around as it varies between 100mV and 900mV which on a OEM narrow band O2 is something like 14.5 to 14.8 air/fuel ratio while in closed loop. What im saying is as long as your between 100mV and 900mV while in closed loop the ECM is doing its thing - mostly for emissions as it could run leaner and definitely not for max pwr.
Im not sure on the knocks 2 degree retard. That is pretty unlikely at idle with good air/fuel. That maybe just a setting or amount of correction used when needed. As that 2* knock retard is hard u believe unless u have a massive amount of initial adv timing set.
Controller area network didnt make sense to me either for that year but thats all i found. CAN could be canister but should read as CANP for canister purge. Anyways i dont think thats a show stopper for your motor.
And i dont know why u think a 350 swap is gonna fix those 2 items. Unless u just really want to do a 350 swap. But again the fueling looks great in closed loop. And that 2* knock retard is hard to believe unless u have a massive amount of initial adv timing set. The worse reading i see is the 108*C (yes i misread the 108 for 100). As that is 'bout 20*C (36*F) hotter than i would run the car.
Swapping to a 350 won't fix your carb's leaky fuel bowl plugs.
Not saying "don't do it"; only, that's a very wrong reason for it. If you want your carb fixed, fix your carb.
The temp is fine for a car w electric fan sitting there idling for a half-hour like that one. Nothing to worry about. It's exactly where it should be.
CAN may very well refer to Canister Purge. That's a good guess.
The carb system doesn't use a duty cycle for the EGR. It's way stupider than that. It's either on or off; no time proportioning. Not really sure what that's talking about, especially in light of it saying "EGR OFF" elsewhere in the printout.
Mixture dwell should be expressed in percent. 48 would indicate a mid range reading and I would assume (with some degree of certainty) that the rich flag and associated O2 voltage are normal. Under normal operation it should constantly swing from lean to rich, as the ecm chases the O2 voltage readings with changes to dwell (at least under constant throttle position).
If I saw a dwell reading up near 70/80ish i'd suspect an ecm responding to a constant rich condition that it could not adjust to.
Again a snapshot doesn't tell the whole story.
The dwell is the percentage of time that the primary rods are 'down', restricting fuel. Because the MCS cycles 10 times a second (up/down) it cannot achieve either 0 or 100 percent dwell.
Thx for elaborating here naf. These fuel systems preceded the internet and theres not much to google with them. I even have a Chiltons just for feedback carbs but it has no acronyms. Who ever has the original CCC and feedback carb info isnt sharing it much.
Much of my knowledge of these systems is empirical. Much of my research turned up incomplete and sometimes contradictory data. I still learn something new about them occasionally.
Yeah there's very little info about that system out there... even back in the day, the code wasn't widely available.
It's just a 6800 series processor, 6805 if memory serves; very little RAM, very small program ROM, slow clock speed. 8-bit. State of the art in 1974. https://en.wikipedia.org/wiki/Motorola_6800
I'm not sure that the dwell reading on that scanner is in percent. I have serious doubts that it is, given that such a reading would be toward the direction of the ECM commanding a middle-of-the-road mixture, while at the same time reporting "rich" down in the text toward the bottom. But I've never just sat and watched the data coming out of the port so I can't say for sure.
naf is correct that the O2 reading should be constantly swinging back & forth between rich and lean. The real actual physical quantity doesn't just stay still anywhere but 0 or 900 mV if it's working right, because its bandwidth is so narrow. It should swing back and forth many times a second. Which given how slow the data stream is, it's not possible for it to capture that.
There's several conflicting informations in that printout, regardless... RPM is 41 in one place, 73 in another; EGR is 58 in one place, OFF in another; baro shows up twice, once with a value and once without... seems like a revisit of its manual might be in order, to understand what the scanner is interpreting about the data it's getting. (the ECM itself sure isn't putting all that text on the wire)
alright guys thanks again good stuff . yeah i at some point i would like to get new 350 . this engine smells , smokes , hard to start when hot , ahh . for now im going to check carb for leaky plugs.
I wanted to mention but forgot to that the health of the engine is found in a compression test and a leakdown test. These will give u cyl wear and cyl leakage diagnosis.
The data log shows mostly the engine controls status.
What im saying is if want to know if its time for new rings or a vlv job use a compression then a leakdown test. And if u need help testing just ask here. Low oil press would be worn brg BTW.
A new 350 won't fix any of that. Every bit of it is related to liquid gasoline laying in the intake manifold. IOW, you can stick a brand new 350 (or 400 even) in there, and if that carb is on it, it will do EXACTLY the same thing.
Pop the carb off. Be SUPER careful not to fornicate the fuel line: hold the big fuel inlet nut still with a 1" open-end wrench while loosening the fuel line nut (5/8"). Take out the long screws you can see around the secondary side that go through the air horn, past the fuel bowl, and all the way down to the throttle plate. Flip it over; take out the screws holding the throttle plate to the fuel bowl. Rotate it up and out of the way, and free of the accelerator pump linkage.
Look at the fuel bowl in that position. Under the primary jets are 2 "tower" looking things, with 2 spun-in plugs each. Those plugs are aluminum, while the fuel bowl itself is chinesium. There is ALWAYS corrosion from electrolysis where those 2 dissimilar metals are in contact. The chinesium erodes, creating a leak with vacuum on one side, and the very bottom of the fuel bowl on the other. The engine literally SUCKS the gasoline past the leak and into the intake. Then when you turn it off and it sits, the fuel steadily drips out into the motor; and when you go to start it, there is (a) a SHIPLOAD of fuel in the intake, and (b) no fuel in the carb. End result is, the car fires a time or 2, blowing black smoke (especially when hot); but then runs out of gas, and you have to whirl it over for like a half-hour to get some gas back into the carb, and when it finally does start again, it struggles and suffers for quite awhile before returning to normal.
Sound familiar?
Cure is, wire-brush those plugs, and the others like them that you can see under the accelerator pump, until you see clean nothing but fresh clean shiny metal. Sterilize them all with lacquer thinner, MEK, acetone, or some similar NON-RESIDUE solvent (NOT brake cleaner, mineral spirits, kerosene) until they are IMMACULATELY SPOTLESS, and cover them liberally with epoxy. Yerbasic JB Weld works fine. Put in a nice hot place and let set up for acoupla hours, at least 4 and preferably more. Reassemble the carb and reinstall with a new gasket.
[QUOTE=sofakingdom;5952424]
I'm not sure that the dwell reading on that scanner is in percent. I have serious doubts that it is, given that such a reading would be toward the direction of the ECM commanding a middle-of-the-road mixture, while at the same time reporting "rich" down in the text toward the bottom. But I've never just sat and watched the data coming out of the port so I can't say for sure.
QUOTE]
All read-outs of dwell I've worked with were in percent. My sample is certainly no proof a universal truth though.
Of interest (at least to me): The diagnostic lead will show dwell as an actual ignition-points type dwell reading although on the six cylinder scale. Interestingly the meter reading AT the MCS is apparently the reverse of the reading at the diagnostic lead. At least as discovered in a post and verified by Damon some years ago.
The 'middle of the road' mixture can be set anywhere within the range of the dwell. It is only set near 50% by adjustment of the IAB. A system working in feedback mode will show the dwell varying approximately +/- 5 percent around some point on the scale. Setting the mid-point of the 'swing' at 50 percent allows the ECM the optimum range of adjustment rich AND lean.
When setting the dwell I have always gotten the system into a feedback mode, finding a spot where the dwell will start varying-confirming that the ECM is adjusting for O2. It could be varying +/- 5 percent around 70 or around 30, etc. Further adjustment of the IAB is then done in small increments to get the 'middle of the road' dwell nearest 50 percent.
I will also note that my 84 LG4 will not show proper dwell reading on my scanner (AX6000). It will show a varying dwell in percent but will read a 'middle of the road' setting around 70ish. I have to use the 'trusty' dwell meter on that one to set dwell at/near 50 percent (scanner still shows 70). Some additional experiential data discounting the veracity of everything displayed on these scanners.
On LG4 models equipped with KS connection of the scanner will disable knock retard and this information will not be displayed, at least in my experience.
08-17-2015, 06:07 PM
good stuff . yeah i at some point i would like to get new 350 . this engine smells , smokes , hard to start when hot , ahh . for now im going to check carb for leaky plugs. 
