spark issue please please please help!!
 

i have an 87 supra turbo (7mgte). and for the past few months i have had a problem with spark. i would hop in 2 minutes after previously driving it and it wouldnt start. then i would replace the coils and it would start again i replaced them twice now and its still doing it. i just recently got my hands on a really nice multimeter and tested all the coils and every single one that i still have that was supposedly "bad" and they all checked out (.3-.5 ohms of resistance).
so now im super confused and i dont know what to do. any help would make me very very happy as this is my only car and it hasnt been running.

please help

I don't know what you're using as a reference, but your measurements sound right on.

Here's a test procedure:
http://www.cygnusx1.net/Supra/Librar...aspx?S=IG&P=12

Please post MKIII specific questions in the MKIII section. I'll move this thread.

ya i know and thanks for moving the thread. i wanna know what do do know. should i check the igniter? or what? thank you for finally helping with this matter by the way

Do you have any diagnostic codes stored? If so, what?


You should go through the troubleshooting chart for ignition problems in the from of the section I linked to. The diagnostic work flow Toyota specifies does work really well. As this is an intermittent issue it probably will be abit harder to diagnose... try to recreate the conditions under which the faults occur: If they usually happen after the car had been run for a while try warming the parts with a hair dryer or hot air gun (set on LOW). If the problems occur when cold, make sure the parts being tested have had time to cool sufficiently.

Troubleshooting work flow:
http://www.cygnusx1.net/Supra/Librar....aspx?S=IG&P=3

Sure, the igniter is a possibility, so is the CPS and ECU. Start with the work flow.

i get codes 12, 14, 21,(maybe 41, i dont remember), 42, 51, 52. i was wondering if it might be the igniter? or maybe the cps (cam position sensor)?

Good god man... :eek3:

Start with fixing the code 41 and the code 12 and code 14. So, yes, troubleshoot the igniter, the CPS and the TPS wiring. Other than the ECU most of those codes have NOTHING in common. It's very unlikely that you're looking at one problem.

tps is good, and the wiring to the cps is all jacked up. how do i test it? i bought a new igniter off my friend ($10 so why not haha). thank you

How is the wiring "all jacked up"?? If the wiring is "jacked up" sufficiently that may be the only thing you need to fix... didn't think it was worth mentioning?

Wiring diagram: http://www.cygnusx1.net/Supra/Librar...x?S=Main&P=040

well the insulation on one of the wires is burnt to a crisp and almost completely off, and all the wires are indistinguishable (they are basically fused together). is there a way to test the cps??

oh and thank you again for your help :D

Sure, you can test the CPS... but it's pointless if the wiring is jacked... why don't you start fixing the problems instead of ignoring them and looking for others? You've wasted a LOT of time by dicking around and ignoring and failing to mention the damaged wiring. :frown:

sorry bout that. so spent all day getting out the old wiring harness and started on the new one. i soldered all iffy connections and such and taped it all with eletrical tape. i will update you once its in. if it works... yay!!!! if not then back to work

well i just pulled out the old harness and fixed up another one i had, tested it then installed it. i jumped my car went to start it and nothing.... almost. It would crank over and it seemed like it only fired on one or to cylinders. i pulled out all the spark plugs and the #2 cylinder plug was completely soaked in oil. cleaned them all and put them back in. i also tried swaping around the plug wires on the coils and i still couldnt get anything.

one question. the order for which plug wire goes where on the coils is 1-6-3-4-2-5, and when the car was running well, i mean really well, it was set up 6-1-4-3-5-2. is there a reason it was running like that???

and the cylinders are numbered 1-2-3-4-5-6 front front to rear correct??

Firing order for a 7MGTE Engine is......
1-5-3-6-2-4
Coil Pack firing order is......
1-6-3-4-2-5
First coil on left, Plug # 1 then # 6 Plug wire into
Middle coil plug # 3 then # 4 plug wire
Third coil on right Plug # 2 then # 5 plug wire
Firing order and coil pack order isnt the same....

yes front to rear. 1 nearest rad.. 6 being the last one.

It's a wasted spark setup.... 1 and 6 BOTH fire at the same time, same for 3 and 4, and the same for 2 and 5.... so, it doesn't matter if 1 or 6 is plugged in to port #1 on the #1 coil pack, just so long as 1 and 6 are the plug wires connected to it. Follow?

yes thank you cre that explains it very well. i assumed that was how it was setup but i wasnt quite sure. now i dont know what to do.

so after screwing with it for another half hour (swapped the coil packs for the bad ones and checked all the connections) i went to turn it over again and it ran for about a second and a half but it didnt seem to fire on all six cylinders. now i dont know where to go with it.

also this may be important or not but there are 3 round green connectors on the harnesses (2 on the driverside and 1 near the thermostat on the passengerside) which are about 3/4 of an inch in diameter and 1 1/2 inches long (approximately). they are bright green and i have no idea where they go. i cant find any connections except when i pulled out the old harness, i found a connection stuck in the connector and it appeared to have broken off a while ago. it lookes like a little round plastic connection that has a bit of metal and a little 2mm long wire sticking out of it. ???

im really confused and as this is my daily driver and i cannot afford a mechanic, i am suffering.

thank you for you help cre and green7mgte

Unplugged/broken connectors = significant. ;)

Sounds like the knock sensor wires and one of the coolant temp sensor wires. Can you post pictures or at least post back with the wire colors? If it's the ones I'm thinking of, the car should still run... it'd run like crap, but it would run.

It's not necessarily going to provide anything useful, but check for diagnostic codes.

i dont have access to the car right now and i dont recall the colors. but where is the temp sensor? because i cant find connetor to plug the connection into

thank you again for the help :)

oh one more question. would the car not start if the o2 sensor was not hooked up?
cuz i heard it would start but run very poorly

It would start... shouldn't even run poorly... just real rich.

Post pictures of the connectors or post up how many wires run to each and what the colors are.

so i found the connection for the green connector by the thermostat... it was right in front of my face... im so dumb lol.
the other green connectors that look the same have on wire going to them and the wires are clear.
here are some pictures. but i also found another connection with a big rubber cover around it. it has one wire going to it and its a square connector. the wire is yellow and black.

oh and the green connectors on the driver side run on the harness right nest to the intake manifold. one on either side of the throttle body. and it looks like they should be run down through the intake manifold and plug into something underneath it. but i dont know where :(

what the hell is that tea cup doing inside your engine bay? man they cram the weirdest t stuff in there. no seriously wtf is that? the green connector plugs into the thermostat housing. but I don't recall ever seeing that plastic cover before.

The one with the rubber boot is the oil pressure sender's connector; The boot covers the sender. Under the exhaust manifold and up from the oil filter... look for a metal can just small enough to fit in that rubber boot.

The matching pair are for the knock sensors. They're located under the intake manifold, one is between cylinders #5 and #6 (between the starter and the block) and the other is up between cylinders #1 and #2.

ok thank you but i still dont know y it wont start

You sure you got the harness patched up correctly? Any error codes (do you know how to check them)?

ya i know how to check them and ive been wanting to all day but its just been non-stop snow here. ill try to run a diagnostic tonight

so after screwing around with it for the past couple days i got it to start. it started 3 or 4 times and died a couple seconds later. so i was really confused and didnt know y. i broke it down and thought about everything one more time, and as i was thinking i realized there was a vacuum hose and a coolant line that i hadnt hooked up. hooked them up and it started. but i couldnt rev it at all. i would touch the gas and it would die. so then i thought a little more and.... bammmmm!!!! i realized i hadnt hooked up the cold start injector and i tried for a little while and didnt have time to hook it up. so im hoping that it was the problem. i will update this thread when ive hooked it up and if it works then yay if not then damn.

also when it warmed up for 15 minutes i was able to rev it but i could only do it slowly. if i just jammed down the gas it would sputter and miss and the rpms wouldnt increase. i just wanted another opinion or two about it. i believe its because of the cold start injector but someone should tell me if that theory is correct.

thank you so much for all the help. i really appreciate it.
oh and i cant find that damn connection for the oil pressure sending unit thing.
and i tested for codes and all i could get was a code 11?? what is that??

so i hooked everything up and it starts right up but when i try to raise the rpms above 2500 it just sputters and loses rpms... why is it doing that?

Off the top of my head possibilities are: knock sensor problems, AFM problem.... I'm not sure if the oil pressure sender being disconnected would cause that, but I think it's unlikely.

Did you get the knock sensors connected? Did you drop the AFM? Did you perhaps spray anything into the AFM (such as a MAF cleaner or brake cleaner)? Have you checked for codes now that the you've had the car running?

As for the oil pressure sender... Follow the yellow arrow. ;)
Attachment 2758


Oh, and the cold start injector ONLY adds fuel WHILE you are cranking. In all but the coldest conditions the car will still start without it, just not without some trouble.

alright so i checked the codes again and all im getting is a 31... afm so i have to figure out what exactly is wrong tomorrow. ill bust into the wiring and hope its just something there if not then ill either replace it, or clean it... or... um... idk what should i do?

Other than blowing some air through it you really can't clean it. It's an optical sensor and trying to clean them usually results in catastrophic failure; In other words, you'll be buying a new one.

The cause of a code 31 could prevent the car from starting and running. With the wiring for the CPS being jacked up, I would be surprised at all if that was the case in other areas as well... How did it get messed up to begin with, do you know?

ok so the wiring to the cps is fine because i changed the harness. the car WILL start it just wont rev up past 2500 rpms. i pulled the o2 sensor and it was covered in soot so, checked codes... 31 afm problem or problem in afm circuit. im going to bust into the wiring tomorrow and see if its the wiring. if its not the wiring, i already ordered a new maf so thatll be in this weekend, hopefully its just the wiring.