so i'm driving home, and suddenly find 2 cyl. missing!

yeah, car was running fine, and i suddenly notice my tach dropping for a second, then cmoing back up, accompanied by the car surging. i pull into a neighborhood street and find myself running on what seems to be about 2 cylinders...
i hook up the logger, check the codes, find a code for ignition coil.
ok, i figure i'll get home, put in a spare coil and be done in 10 minutes. well, 10 minutes later, i fire it up, still on 2 cylinders!!!!

oh, my afc rpm and stock tach no longer match. afc is double what the tach says.


what controls the coil packs to make only one of them not work? what can i check and test? aren't they directly controlled by the ecu? would a faulty ecu cause this?
thanks!

 

[spoulson]

Check the MPI relay harness under the pass dash, next to ECU. I had this come loose and cause that problem.

Next, check the power transistor and coilpack connections. Check spark plugs to see which ones are rich, 1/4 or 2/3, to determine which coil is not firing. The front coil is 1/4 IIRC. If the coils just suddenly stop firing, it's likely a connection problem.

 

well... 2/3 aren't firing. my connections are good, since i swapped out the transistor and coil packs and i made sure they were tight and clean.
however, i will check that harness...

 

The coil that fires both plugs 2 and 3 is driven from the pin #1 output of the transistor, which in turn is driven on transistor pin #3 by ECU pin #55.

 

[tsiboy]

i had something similar happen to me

check the harness going to your CAS or the CAS itself may be bad.

-alex

 

Quote:
The coil that fires both plugs 2 and 3 is driven from the pin #1 output of the transistor, which in turn is driven on transistor pin #3 by ECU pin #55.



that's what i was looking for... what kind of voltage should i see from the ecu on pin 55?

 

Quote:
i had something similar happen to me

check the harness going to your CAS or the CAS itself may be bad.

-alex



i've been doing some searching and this particular sypmtom has shown the cas to be at fault a couple times... now i just need to find another pigtail cas...i have several 91+ style but no other pigtails.

 

[Garage_Defeat]

I've got a 90 pigtail cas. pm me.

-Dan S.

 

can i just splice a 91+ style plug to the 90 cas harness to be able to use the 91 cas? it' sjust 4 wires right? that way i'll be able to use a more readiliy available cas in the future too...

 

another question though... if the cas was bad, wouldn't i get a code for it? my only code is for the ignition coil, #44...

 

It could also be your injectors not firing. I think one of the injector drivers when out in you ecu. Check and see if all you cylinders are firing, if they are, you have an injector driver problem.

 

cyls. 1 and 4 fire, 2 and 3 no fire. that combined iwth the code 44 leads me to an ignition problem...

 

The ECU will throw code #44 if for any reason its not seeing the ignition pulse. So, that pretty much brings you back to square one: ECU, transistor, to coil pack. I'd swap transistor and see what happens. Did your ECU ever have acid damage?

 

i swapped teh transistor yesterday, no good. will swap ecu's today and see what happens.

 

[Hertz]

Quote:
oh, my afc rpm and stock tach no longer match. afc is double what the tach says.



You need to make sure that the AFC is set for a 2-cyl application because of our wasted spark system.
http://members.shaw.ca/costall/1000Q/Frameless/answers-SAFC.htm

 

well that was my immediate first thought, but then i thought "the afc has been installed for weeks in here and rpms always matched".

keydiver- i did inspect the ecu before i put it in the car a couple months ago and it seemed like it was fine, but it is old and could have deteriorated in the past couple weeks...

 

[tsiboy]

Quote:
can i just splice a 91+ style plug to the 90 cas harness to be able to use the 91 cas? it' sjust 4 wires right? that way i'll be able to use a more readiliy available cas in the future too...



you have a 90 style cas??? might as well switch it out even if its not the problem. the part of the harness that connects to the CAS gets all oily and the wires get cooked and become very brittle.

 

yea i have a 90 style cas... this is all happening in my 90 ggs-x turbo swapped car.
plugged in a good ecu, still no fire to 2 and 3. haven't had time to swap the cas yet...

 

well, just put in known good cas... still no good!
so far i have put in known good
1.coil pack
2.transistor
3.ecu
4.cas

i still have no spark on 2/3.

any other ideas?
i can check for voltage from the ecu at the ecu pin 55 right? what V should i be seeing if it's functioning properly?
where does it go from there?
can someone give me a power flow diagram that i can trace with a dvom?

thanks!

 

someone tell me if i have this right...
power goes to cas, cas spins, sends signal to ecu telling it to fire either 1/4 or 2/3 coil. ecu sends signal to transistor which then sends to proper coil.
so i either have a continuity problem from the cas to the ecu or the ecu to the transistor or the transistor to the coil on the wires that control 2/3 coil.
anybody know the wire colors appropriate to test?