No difference unplugging coils 4, 5 & 6

[CSquared]

Car ran great the first weekend I got it up and when I took it out the next weekend I started having these limp mode type issues that are driving me crazy. The car idles sub 10 afr like a bag of balls and hesitates to rev. (Aristo swap, single turbo , stock fuel aside from a SAFC and no check engine light). Tried a 2nd ecu, replaced map sensor and bunch of other little things but nothing has worked.

After catching another thread I decided to test my coil packs by unplugging them one at a time. Here were the results numbered from the front of the engine bay to the rear:

Unplug coil 1: Car runs shitty(er) and immediatly runs better when plugged back in.
Unplug coil 2: Car runs shitty(er) and immediatly runs better when plugged back in.
Unplug coil 3: Car runs shitty(er) and immediatly runs better when plugged back in.
Unplug coil 4: Made no difference in how shitty the car was running.
Unplug coil 5: Made no difference in how shitty the car was running.
Unplug coil 6: Made no difference in how shitty the car was running.

Then I decided for the hell of it to unplug 4, 5 & 6 at the same time which stalled the car immediately upon startup. Then any combination such as 4-5, 4-6, or 5-6 made the car stall just the same. THEN I tested each cylinder for spark and there is good spark on every cylinder.

WTF is wrong with my car? I am tired of spending money chasing this issue around.

---------- Post added at 04:48 PM ---------- Previous post was at 04:40 PM ----------

On a side note the nice folks who did my harness suggested a general grounding or specific coil pack grounding issue. The 2jz coils are grounded to the engine I assume being bolted to the head?

Also where did you guys do your engine grounds. I'm sure I'll miss one or two that I have but these are mine:
1. Firewall to rear coil pack
2. Firewall to rear tow hook
3. battery to body
4. bellhousing to body
5. tranny to trannymount/body

I can't find a good place to bolt directly to the head.

 

[destrux]

Most likely an igniter problem, or a wiring problem to the igniter.

I'd also use a spark tester and test the coils with them unbolted. The coils on the JZ motors usually don't completely fail like that, they normally crack and leak sparks around the tower or mounting bolts and the engine runs poorly under boost or when it gets wet.

 

[CSquared]

I was under the impression that either the ignitor works or it doesn't. I'm going to be redoing my grounds tomorrow and I will take a look to see if anything got fubared with the wiring. God I hate to spend another hundred something bucks on a part in desperation.

 

[D.J.T.]

Are you getting Spark? Do you have good compression in those cylinders? If both are good your probably looking at the injectors.. my MK2 did the same in two cylinders. bought seafoam & used & 1 injector got cleaned. i Replaced Cylinder 6's injector & now it runs perfect. Could be that power isn't reaching the injectors too. So check that with a tester.

 

[destrux]

Yeah I had a brain fart there and forgot about the fuel and compression side of things. Been dealing with alot of ignition issues on several cars lately so I've got spark on the brain.

The ignitor can burn partway out though. I haven't seen it on a supra, but I have on other COP/DIS cars.

 

[CSquared]

Are you getting Spark? Do you have good compression in those cylinders? If both are good your probably looking at the injectors.. my MK2 did the same in two cylinders. bought seafoam & used & 1 injector got cleaned. i Replaced Cylinder 6's injector & now it runs perfect. Could be that power isn't reaching the injectors too. So check that with a tester.

Well I re-did the grounds and same BS.

I think I am going to check compression next weekend but as far as injectors, would the car still be running way rich if clogged or not getting power? Then regarding spark, I haven't checked since the car was first running right but I will recheck this weekend.

The ignitor can burn partway out though. I haven't seen it on a supra, but I have on other COP/DIS cars.

And if it does go partially then I shouldn't be getting any spark? Or is it possible there is a weak spark?

Another thing I intend to look at is the timing gear behind the crank pulley. I've head that sometimes separates although I imagine there would be a code.

 

[CSquared]

bump

 

[D.J.T.]

To check for spark is quite simple. Just pull the wire plug & if you hear a ticking noise theres spark in the wire & you should be able to see the spark. If theres good compression & spark its your injectors not working, either theyre clogged, or electrically damaged.. I guarantee it.

 

[Vrank!!!]

I injectors could get stuck open....

 

[dirosa]

look at the plugs. compare 1-3 with 4-6. if your injectors are stuck open (say from leaky ecu capacitors), your plugs will be black. also, disconnect the coil packs and crank it over for a few seconds, then pull the plugs, and there should be some fuel on all the plugs which tells you if the injectors are all firing........after all that, i would suspect ignitor and/or wiring to coils.

 

[CSquared]

Yeah I have no problem testing the spark. Last time I rigged up a ground wire to the coil pack but I only spot checked a few cylinders because I just wanted to know if the car was making any spark. Then the car started and ran great so I didn't have to bother going any further, but now at this point I will.

I know the injectors are potentially a problem but they only have about 70K on them and were cleaned and flow tested before install so I will probably address them after the verifying spark on all cylinders this weekend. Also I had all of the capacitors replaced on my ECU by driftmotion (and tried a 2nd ecu) so I'm leaning away from that too.

lol if I only listed the full series of what I have tested and replaced at this point you would be amazed, but I really am/was hoping to narrow it down with this thread.

 

[honeydew]

WTF is wrong with my car? I am tired of spending money chasing this issue around.

That. is hilarious.

Kinda sounds like a speed or TPS. or some crimp somewhere came loose. Skipped a tooth timing wise? No codes?

 

[CSquared]

No codes, good spark on all cylinders, re-did timing... Seriously man shit is driving me crazy.

 

[johnd]

this sounds like something that would happen to me,:thumbsdow start the car and take a long screw driver and set it on the injector and hold it up to your ear you can clearly hear the tic.
If you have spark and your injectors work then it has to be a wiring issue, almost sounds like there not batch correctly.

 

[CSquared]

I'm planning on killing any doubts about the injectors and pulling them this weekend for another clean and flow test. Then I'll look at the wiring. I really don't think anything was wired up wrong because the car seriously ran great the first weekend I got it running. I mean it ran smoother than the stock 7m days and then I come back and it is mysteriously running like shit. So needless to say the dickish ray of hope it gave me has since been squashed.

None the less I figure when I pull the top of the manifold off for the injectors I can better double check for frayed wires and that kind of bs. It's an f'ing jungle on that side of the motor.

 

[kneedragger85]

I just got rid of my Code 14 which prevented me from reving over 2k rpm and gave me no spark in #6. I pretty much did all the same tests you did with continuity between IG1-IG6, continuity between Igniter to coil grounds 1-6, tested another igniter and ecu, tested another set of coils, found 12volts at the coils etc etc etc... I fixed it by peeling off the wiring insulation to each coil wire (found some frayed 12v and ground wires grounding/bypassing the coils) and wrapping electrical tape over the open wires.

 

[CSquared]

lol so I uninstalled the SAFC and nothing... Then I bit the bullet and checked compression and there is absolute ZERO on 4 & 6. Awesome. I am going to pull the head this week praying for valve issues.

How the hell does this thing run?

 

[johnd]

absolute ZERO on 4 & 6. Awesome
Your a 1 off.:naughty::nono:

 

[D.J.T.]

No compression means either... piston rings are worn, or the Valves aren't closing.
But you already know that.

 

[CSquared]

Yeah so maybe I figured it out.



Decided to see if I could find any stuck valves by eye, turned the cam gear and yelled "HOLY SHIT!"... Seriously did not make any noises whatsoever and I guess it must have cracked on start up the first time the car started running shitty. Torqued to factory specs in order per TSRM and clearances measured 100% in spec.

Guess I'll just grab another cam and see.