lastchance Posted May 10, 2013 Share Posted May 10, 2013 I'm trying to diagnose some misfire/rough running/idle issues with my 84 turbo wagon but the light on the front of my ECM stays on. I pulled the cover under the column off, located the green T-connector and have tried numerous ways to get the light to turn off. I've ran codes before with no problems whatsoever, but this time I'm having issues. With the car either running or in the ON key position, the green T-connector connected or not - regardless the light on the ECM just stays lit. Could the ECM be failing? Is there a way to reset it? Is there perhaps more than just that one green T-connector that I'm not seeing? Link to comment Share on other sites More sharing options...
lastchance Posted May 10, 2013 Author Share Posted May 10, 2013 to note: the car started running poorly with a bad misfire that seems intermittent and i'm trying to track down the issue. symptoms: car starts every time, but runs rough most of the time, sometimes it idles great and runs through the entire powerband but most often it runs really rough. i have to keep the RPMs up when in DRIVE or PARK by revving, even then the engine isn't running smoothly and seems to have a pretty bad misfire. if i start the car and let it rev by itself when cold it'll run for a few seconds then the RPMs will drop, the car chokes and sputters, then dies. if it's warm it'll do the same thing. actions already taken: checked injectors, replaced fuel filter (~100 miles ago), full tank of gas, checked for vacuum leaks, cleaned the EGR valve (~100 miles ago), replaced PCV valve (~100 miles ago), checked for disty shaft play, made sure (NGK) plug wires were all tight and not damaged. Link to comment Share on other sites More sharing options...
Turbone Posted May 11, 2013 Share Posted May 11, 2013 Easiest way to reset the ECU is to disconnect the battery for 20min or so. What about the coil, done anything with that? I've had a few go out on me with EA81T's and EA82T's. Link to comment Share on other sites More sharing options...
nipper Posted May 11, 2013 Share Posted May 11, 2013 If you are having a problem pulling codes I would suspect an ecu, but first rule out all the common plugs/wires/coil/fuel stuff. Link to comment Share on other sites More sharing options...
lastchance Posted May 11, 2013 Author Share Posted May 11, 2013 Easiest way to reset the ECU is to disconnect the battery for 20min or so. What about the coil, done anything with that? I've had a few go out on me with EA81T's and EA82T's. Cool, i'll disconnect the battery and make sure to get those codes cleared/reset. i originally thought the coil, but figured coils just die not fail over time. the coil is original to the car, so it's almost 30 years old. i'll test that for sure. they can act shotty before they finally completely die? If you are having a problem pulling codes I would suspect an ecu, but first rule out all the common plugs/wires/coil/fuel stuff. i'll reset the ecu like turbone said then try to grab codes again, i'm hoping it's just that simple. plugs, wires are both good. coil is the next thing i'll check. thanks guys! Link to comment Share on other sites More sharing options...
Turbone Posted May 11, 2013 Share Posted May 11, 2013 Yes,a coil can start to act dodgy for a while before going out. The car will run like crap and when the coil overheats, it will quit working and the car wont run. Then after it cools off it will start again. Wash, rinse, repeat. Link to comment Share on other sites More sharing options...
nipper Posted May 11, 2013 Share Posted May 11, 2013 Coils die slow painful deaths. If the coil lays on its side, they will sometimes miss only when you make a turn or the car is leaning to one side. They will fail when they get hot but start fine when they are cold. The older can type coils use an oil between the coils of wire as an insulator. With time and heat the oil breaks down which reduces the strength of the spark, or can make for no spark at all. Link to comment Share on other sites More sharing options...
lastchance Posted May 12, 2013 Author Share Posted May 12, 2013 i got the light on the ecu reset, ran codes and it pulled 11 and 12 which i understand are nothing to worry about. thanks for that guys. i see there's no trouble code related to the coil, and after testing it (across the + and -) it's showing resistance of 1.7-1.8 ohms. is that normal? is there another coil test i can do? Link to comment Share on other sites More sharing options...
lastchance Posted May 12, 2013 Author Share Posted May 12, 2013 ooops, i just realized you can test resistance at the 20k setting between one of the posts (+ i believe) and the center main disty cap wire. i'm getting 8,560 ohms there... normal or not? Link to comment Share on other sites More sharing options...
nipper Posted May 12, 2013 Share Posted May 12, 2013 I honestly would just swap another coil in and see what happens. It is hard to bench test a weak coil as not only do you need the heat, but you also need the 60kv to test the insulation. 1 Link to comment Share on other sites More sharing options...
lastchance Posted May 12, 2013 Author Share Posted May 12, 2013 gotcha. makes sense. i'll hunt one down and see what happens. thanks again. Link to comment Share on other sites More sharing options...
naru Posted May 12, 2013 Share Posted May 12, 2013 i got the light on the ecu reset, ran codes and it pulled 11 and 12 which i understand are nothing to worry about. thanks for that guys. i see there's no trouble code related to the coil, and after testing it (across the + and -) it's showing resistance of 1.7-1.8 ohms. is that normal? is there another coil test i can do? Specs for an ea-81t coil secondary winding are 8000-12000 ohms so you are good there. Primary is .84-1.02 ohms,however. Reading resistances that low can be tricky.Does your meter "zero" properly w/the leads shorted? Check it w/a one ohm resistor ,if you have one. I would shake the coil around w/the ohmeter attached to see if the reading changes. A worthy coil test is to observe the strength of spark w/an inexpensive spark tester w/an adjustable gap. If the spark jumps a lenghty gap,coil is OK at that moment at least. IME,coil failures are few and far between.Never say never though. Be careful w/any coil subsitutions. Some aftermarket coils may cause problems for your expensive ignition module. Still running poorly after ECU reset? Check plug wire resistance. How do the spark plugs look? All the same? Fuel pressure should be checked early in the diagnosis. I would remove plug wires one at a time ,attempting to isolate the dead cylinder. Link to comment Share on other sites More sharing options...
nipper Posted May 12, 2013 Share Posted May 12, 2013 (edited) Coil failures are rare in coils as a group. They are not rare in 20 plus years old can type coils that have never been replaced. Edited May 12, 2013 by nipper 1 Link to comment Share on other sites More sharing options...
lastchance Posted May 12, 2013 Author Share Posted May 12, 2013 (edited) Specs for an ea-81t coil secondary winding are 8000-12000 ohms so you are good there. Primary is .84-1.02 ohms,however. Reading resistances that low can be tricky.Does your meter "zero" properly w/the leads shorted? Check it w/a one ohm resistor ,if you have one. I would shake the coil around w/the ohmeter attached to see if the reading changes. A worthy coil test is to observe the strength of spark w/an inexpensive spark tester w/an adjustable gap. If the spark jumps a lenghty gap,coil is OK at that moment at least. IME,coil failures are few and far between.Never say never though. Be careful w/any coil subsitutions. Some aftermarket coils may cause problems for your expensive ignition module. Still running poorly after ECU reset? Check plug wire resistance. How do the spark plugs look? All the same? Fuel pressure should be checked early in the diagnosis. I would remove plug wires one at a time ,attempting to isolate the dead cylinder. the plugs are new (about 100 miles old) and all seem to have about the same amount of 'wear'. i'll check the fuel pressure, didn't think of that. Coil failures are rare in coils as a group. They are not rare in 20 plus years old can type coils that have never been replaced. that's what i'm hoping, that the coil just died due to age rather than internal failure, etc. on a side note, years ago (probably 2002-ish) i ran an accel super stock for about a week before it died and left me stranded, i put the stock unit back in and it's lasted this long. hahaha! Edited May 16, 2013 by lastchance Link to comment Share on other sites More sharing options...
Turbone Posted May 12, 2013 Share Posted May 12, 2013 Accel coils are notorious for failing within a year of use. I use a MSD on my Brat. Link to comment Share on other sites More sharing options...
lastchance Posted May 12, 2013 Author Share Posted May 12, 2013 Accel coils are notorious for failing within a year of use. I use a MSD on my Brat. like the blaster 2 type? not the huuuuuge racing one, right? Link to comment Share on other sites More sharing options...
TallonX Posted May 14, 2013 Share Posted May 14, 2013 Couple things on coils... Paper is the insulator oil is heat exchange. Voltage in is in correlation with voltage out ie; 60000v out is equal to 12v in with 5000 wraps, this is the reason why the resistance values are important OEM vs. Aftermarket coils... OEM allows for a miss 20% of the time aftermarked 5-10% Just as long as you keep within OEM specs on primary resistance when you buy aftermarket you should be fine. Personally I run a MSD High Vibration coil. Link to comment Share on other sites More sharing options...
lastchance Posted May 15, 2013 Author Share Posted May 15, 2013 Couple things on coils... Paper is the insulator oil is heat exchange. Voltage in is in correlation with voltage out ie; 60000v out is equal to 12v in with 5000 wraps, this is the reason why the resistance values are important OEM vs. Aftermarket coils... OEM allows for a miss 20% of the time aftermarked 5-10% Just as long as you keep within OEM specs on primary resistance when you buy aftermarket you should be fine. Personally I run a MSD High Vibration coil. great info, thanks for that. i picked up a new coil last night and will install this afternoon, will keep you guys posted on the outcome. Link to comment Share on other sites More sharing options...
lastchance Posted May 15, 2013 Author Share Posted May 15, 2013 installed the new coil, same issues. I noticed one of the negative ( - ) wires on the coil was a cracked and seemed to be holding on by just a few strands of wire inside the insulation. it's probably in my best interest to fix that just to rule out the coil and wiring. Link to comment Share on other sites More sharing options...
TallonX Posted May 16, 2013 Share Posted May 16, 2013 (edited) What's your timing set at? 8 before on fool infected 20 before on carbed. Running premium fuel? Sorry my bad tubo'd is 20 btdc as well Edited May 16, 2013 by TallonX Link to comment Share on other sites More sharing options...
lastchance Posted May 16, 2013 Author Share Posted May 16, 2013 (edited) i've owned the car since 1999 and only ever ran premium gas, the timing however... i don't know. i've never timed a car or looked at the timing on this one. it's not possible for a pushrod engine to "fall out" of timing is it? i'll check the resistance on the coil wires when i get home, figured that'd be a quick thing to rule out. Edited May 16, 2013 by lastchance Link to comment Share on other sites More sharing options...
naru Posted May 16, 2013 Share Posted May 16, 2013 What's your timing set at? 8 before on fool infected 20 before on carbed. Running premium fuel? Sorry my bad tubo'd is 20 btdc as well EA-81Ts are 15 btdc not 20. Link to comment Share on other sites More sharing options...
ivans imports Posted May 16, 2013 Share Posted May 16, 2013 have 2 84 turbo ecus left Link to comment Share on other sites More sharing options...
lastchance Posted May 16, 2013 Author Share Posted May 16, 2013 have 2 84 turbo ecus left kinda funny considering i got the trouble codes reset, pulled code 11 and 12, then the light went back to being stuck on. i'm wondering if it's the ECU that's dying, i left the battery unhooked overnight and will see if it does the same thing again this afternoon. otherwise... $$$ ??? Link to comment Share on other sites More sharing options...
lastchance Posted May 17, 2013 Author Share Posted May 17, 2013 I left the battery disconnected overnight, reconnected it this afternoon and it throws codes 11 and 12, then the light stays on as before. I did a voltage check on the battery just in case, both sitting and also running - good power coming from that Optima! I also checked the resistence on the plug wires: 2,200 2,410 4,770 5,260 9,270 Obviously from shortest to longest, so those are fine. I started the car and it idled fine for as long as I let it, only after a few starts in which I'd turn the key, let the car rev naturally to ~1200 rpm, then watch the RPM's fall off like it couldn't hold onto the cold start RPM range on it's own. Weird. Link to comment Share on other sites More sharing options...
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