Coil Packs won't fire in #1 position.

I have a I have a very rough idle that I narrowed down to a coil pack that won't fire in the #1 position (disconnected the connector on the coil while the engine was running and there was no change at the #1 position. The other two killed the engine immediately when disconnected). I swapped coil packs and the problem remains at the #1 cylinder. Checked for firing voltage at the connector and it is good (12.4 VDC with the key on). Suspect the computer is not providing a ground for the coil to fire. So, sounds like wiring to the computer or the computer. Any ideas on further troubleshooting I can do, where I can get the computer tested, etc???
Didn't mention it's an 03 3.4 V6

 

New development... When accelerator depressed to begin manual activation of the throttle plate (overriding the computer input) and RPMs reach about 1100, engine smooths out and runs great. If I pull the connector off the #1 coil pack (at 1100 RPM) it kills the engine like the other two do if I disconnect them at idle. Any ideas on what would cause a problem with the #1 coil pack not firing until the RPM is up to 1100??? As stated above, I have swapped coil packs around with no change to the symptom.

 

More research... Got a suggestion to check the igniter (or ignition control unit/module). As I understand it, the igniter/ICU/M passes the ground from the coil pack connector to the ECU (computer). When the ECU wants to fire the coil, it directs the igniter/ICU/M to open the coil ground. This causes the coil to discharge through the spark plug. Haven't figured out a way yet to simulate the computer command to the igniter/ICU/M to fire the plug. Anyone have any knowledge on this?
Surely someone else out there has had this problem and can provide some insight to a solution??? Prices for a new igniter/ICU/M run from $200 to $713.99 at Autozone. Looking for a good used one with some kind of warranty. Anyone have any ideas????
Moderators... am I posting this correctly? Is it available to everyone? Please advise.

 

Free bump. I don't have an answer for your problem but I have been watching to see what you find. Hopefully somebody will speak up.

 

BDN, Thanks for the response. At least now I know I'm getting out there. I have an appointment tomorrow morning to get the computer reflashed at the Toyota dealer. Taking the igniter too, to see if they can test it. I'll post the results of that and cost to do the reflash.

 

Have you checked that plug? I had a friend last year that had a 6 CYL (not a Taco) that was missing, sometimes at idle, sometimes not. He replaced the coil, he traced the wiring. FINALLY replaced the plug and boom, ran like a charm. I have had this happen even in something so simple as a 4-stroke Honda weed-eater. Would crank, idle, but run it up and it would sound EXACTLY like it was running out of fuel. Several carb cleanouts, then fuel tank and filter/"clunk". No better. Finally replaced the carbs. No better. So I thought "what else?" On a whim I replaced the plug and it is like new again. But I wasn't satisfied. I have an old model-T spark coil (for anyone that knows what that is.) I set it up with that plug, turned it on, and solid spark. Took my MAP torch and started applying heat and very quickly no spark. Into a dark room, same thing, and when it stopped firing I turned the torch off. And up inside the plug, the spark was jumping through a crack in the tip insulator that would apparently open up just enough when it got hot.

Not very convinced it is your problem, but it is a "cheap try."

 

Thanks for the reply. I have changed the plugs. At the time I had not heard of the potential issues with running "normal" plugs vs. Denso dual electrode plugs, and installed some titanium single electrode plugs. Had this idle problem and bought some Denso dual electrode plugs. No change in performance. Still very rough up to 1100 RPM and #1 (and 4) coil packs not firing. Hoping this re-flash of the ECU I have scheduled for today will take care of it. Will post results.

 

So... Toyota dealer said couldn't test the computer (ECU) or the igniter/ignition control unit/module with it out of the truck. Had to wait a couple of days for an appointment. Towed it down and left it for a day. They told me I had a bad throttle body and nothing else. I knew I had a bad Accelerator Pedal Position Sensor on the throttle body and already had one on order. Started the truck, showed them the rough idle, disconnected the #1 coil pack connector... no change in idle. They said they had never seen that condition before. This the Head service guy, the assigned service manager and their only Master Technician. Suggested I leave the truck for a while to see if they could come up with something. Towed the truck home. Ordered a new (used) igniter on line from the same place I ordered the Throttle body. They said they were going to send both together... Got the box. No igniter. Installed the new throttle body. Now, when I accelerate, the engine RPM increases in direct proportion to the amount of movement of the accelerator input (instead of nothing happening until I rotate the mechanical input where the accelerator cable connects about 40 degrees, when the butterfly valve starts to move from the physical input rather than the computer input). BUT.... still have a miss from idle to 1100 RPM. Pull the #1 coil pack connector and no change. Contacted the company... they decided their igniter/ignition control module was bad and didn't send. Now looking for another one. All suggestions welcomed.

 

Got the throttle body. Fixed the problem with the APPS. Got the new (used with warranty) igniter and installed it. Had the battery disconnected for a day or so because I heard there could be some issues with codes etc. Cleared the code for the APPS with my OBDII scanner. Started it up, ran for a while, still had the rough idle. Shut it off and checked the codes. NO codes..... I went back through all the wiring (12 vdc to the coil pack when the key is turned on, ground path from the coil pack connector to the igniter, all other wiring from the igniter to the computer, etc. All still good. I am now planning to build a test cable between the coil pack and the coil pack connector. I'll remove the coil pack, flip it over, and install my test sparkplug with a ground clip. Theoretically, if I turn the key on (12 volts to the coil pack), then open the ground path from the coil pack to the igniter with everything else still connected, it should force the coil pack to discharge through the test sparkplug. If that happens, I have to believe the problem is in the computer not giving the igniter the command to open the coil pack ground.
So far, I have installed new coil packs and jumper wires to the driver side plugs, swapped coil packs to make sure a new one wasn't bad, changed spark plugs, replaced the igniter, swapped fuel injectors, installed a new fuel pump (don't ask), replaced the fuel pressure regulator, added new grounds to the throttle body and the intake manifold, verified voltage to the coil pack with key on, ohm'ed out all the associated wiring while massaging the wires, etc., etc.
If anyone has any suggestions, I'm open to anything at this point.
I would really appreciate it if someone would acknowledge this post, if only to say they saw it. Thanks

 

Your post has been viewed by 137 members so far. Apparently we are all clueless but we're here to see what you come up with.
Don't give up man.

 

I hope I don't send you astray, just something nagging me about the coil pack and the #1 cylinder, the coil pack fires for 2 plugs, at the same time. It uses a wasted spark (?) kind of system. So if the pack was bad on #1 it should be bad, or have the same effect when you pull the boot from the opposite plug as well. Have you changed the plug wires?

 

You sound savvy enough to keep on with the diagnostics but keep in mind the high voltage, secondary coil winding is not grounded and both plugs fire in series within the secondary winding circuit. The engine block (ground) acts like a conductor between the 2 plugs as opposed to a conventional ground.

I will add this. A while back a fellow had one wire come out or break in the igniter plug, the igniter itself was fine.

 

BDN - Yes, I installed new wires from the coil packs to the driver side plugs and new dual electrode plugs. Today I tried something different. Removed all plugs from the engine. flipped the three (new) coil packs and (new) driver side plug wire jumpers (from the coil packs) over. Reinstalled the (new) plugs and using some heavy duty ground wires with large spring alligator clips, grounded all six spark from the base (threads) to engine ground. This gave me the ability to view all spark plugs as I cranked the engine over. All plugs fired immediately when my wife started cranking the engine, then #1 and #4 stopped firing after the first spark. The other 4 spark plugs continued firing as long as the engine was cranking. Tried it 3 times with the same results. Reinstalled all plugs, coil packs, driver side plug wire jumpers and tried starting it again... Still has rough idle that magically smooths out at about 1000 RPM (reminds me of my lawnmower running rough after starting with the choke on, then smoothing out after turning the choke off). And as I said before, I did swap the fuel injectors around. After a LOT of additional research, I'm considering a new crank position sensor. Don't really believe that is the problem, but that is part of the timing for this engine. Don't understand how it would only effect #1 position or start working correctly after 1000 RPM. I'm thinking it looks more and more like the computer.

Dirty Pool, thanks for the diagrams and advice. Now the bipolar plugs make sense. I ohm'ed out all the wires in the igniter plug, including the wires between the igniter and the computer, moving the wires/connectors at the same time.

 

Sent the ECU (computer) to SAI Electronics in Tilden, IL. They are in the business of testing and repairing (if necessary) ECUs. If they test mine and find no problem it gives me peace of mind and I know the problem is elsewhere. If they find a problem and repair it, I get MY ECU back (repaired and verified good) with no worries about a compatibility issue (at a much cheaper cost than buying a new one).

 

Hi i have the same problem with a g15a engine. 1of the coil pack will. Not. Fire. I have change all yhe same things. Same problem. Did u find a solution. For this i feel it cud be the ecu also any suggestions?

 

Did you check compression, especially on #1? Weak conpression will give you a miss at idle, but when revved up a little it will carry it thru (smooth out).

 

I found a broken tooth on the reluctor wheel on the back of the crankshaft timing belt gear. The crank position sensor reads these teeth as the engine rotates and sends a timing signal to the computer, which sends a signal to the igniter to take the ground away from the coil pack and allow the coil pack to fire through the spark plug. I changed my computer (ECU) but still had the problem. Just happened to see this broken tooth when looking at a picture of the engine while on an engine stand. Changed the crank timing belt gear (with reluctor wheel) and it fixed everything. Unless you have had your engine out, you probably don't have this problem, it's probably the igniter or ECU. I've attached a picture of the engine that shows the engine on an engine stand. If you blow up the picture and look at the bottom gear for the timing belt, you can see the broken tooth at the top of the gear, just to the right of the timing mark.

 

I changed. The ecu and coil pack same problem. Fire on only coilpack 2 to 3 none on coil pack. 4to 1 injextors new. I think. I hust not geting pulse. To it bcuz i bridge a wire. From the coil wire.On d next coil pack and its fire but weak. I open ecu and saw ignition 1 and ignition 2 where the wire connected to ignition. 1 fires but 2 dont cud it b a coincidence. That the two ecu have the same fault. Or sumthing else help

 

The car idles. But rough wen tumbling the coil fires but coil stop wen start and keep hearing a miss

 

One of the leads in the coil connector is 12 VDC from the key when starting or running. Need to verify you have that voltage at your problem coil. The other lead is ground. Check for direct continuity from the coil connector to the igniter connector. Then check for a good ground from the igniter connector to engine ground. Buying a Toyota repair manual with wiring diagrams for your vehicle from an auto parts place would be a good idea. Good luck