Issues after valve cover gaskets

[Car Guy]

I did valve cover gaskets on a 2008 LC and had what feels like a misfire upon re-start. The CEL, ‘4LO’, and traction control light are all illuminated, with the CEL and ‘4LO’ constantly flashing. The job went very smooth and this was a total surprise. I re-looked everything over about 5 times and can’t find anything unplugged or out of the ordinary. The wiring harness from the factory is sorted well enough where mixing coil pack wires is not easy. Next step is to try finding a code scanner. Until then I’m hoping somebody might be able to shed some light on this. My only feasible thought at this point is I disconnected wires at the fuse box that needed constant power and something needs to be reset. Any help with this is much appreciated!!!


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[OregonLC]

Yeah, you probably do have a misfire. Either something's not fully connected or it was broken on R&R. Code will tell the story.

If it's running then your problem isn't with at the fuse box, it's with a coil or injector (there are no cylinder-specific fuses).

 

[ckkone]

Sounds like a coil pack issue, you could unplug one coil pack at a time with the engine running. Unplugging a properly working coil should make the engine run even rougher. If the engine doesn't change, then that coil pack isn't working.

 

[options2]

I dont know if it is even possible. I have not look at the cable lengths.......but is it possible to plug the coilpack to the wrong connector. In a sense being out of order and firing at the wrong time?

Or is that not physically possibly due to the wiring harness?

I only ask because I have seen this before on an older car, it was firing out of order.

 

[OregonLC]

Not really possible. Each connector is at the minimum length. As @ckkone suggested, just start unplugging one by one and the one that has no change is your misfire. Then you can swap coils between it and a known good cylinder. If the problem stays then it's an injector or spark plug problem. If it travels with the coil its a coil problem. If it's fixed it was a loose connection. Either way, you'll hone right in on it.

 

[Car Guy]

I should have mentioned all 8 coil packs and spark plugs are 1k old and everything has been running flawlessly. A lot of work ($2k in Toyota parts) was recently done to this LC. This work was last on the list as I noticed oil in the spark plug wells when changing the plugs a few weeks ago.

As OregonLC mentioned, due to a well sorted wiring harness mixing coil pack wires is difficult. In the end this was a lot to do about NOTHING. Nothing was mixed up, left unplugged, incorrectly installed, etc... After one battery reset, things ran marginally better. After a second reset, eveything now runs flawlessly. By the time I connected the scanner (after the second reset) there was no codes to be found anywhere. I also tested the battery and alternator and they are all good.


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[Hoosier Daddy]

Did you happen to have the Ignition "on' but not running at any time during the process? I recently unplugged the MAF sensor in my Lexus car and then briefly had the ignition on while the MAF was out. Engine was off the entire time, but it still threw a code upon first restart after reassembly.

 

[Car Guy]

Everything was off the entire time.

 

[VooDoo2]

Put your batteries on charge. On startup the car does a self test. Im also betting you dont use the CDL much. It can get sticky and is part of the self test on start. You also need a decent charge to run the ECU's. It could simply be low power. Ive seen this quite a few times. Enough to start the car, not enough to keep it running

 

[Car Guy]

A week ago a misfire on #1 cylinder appeared out of nowhere. Everything was running flawless since this(the reason I posted this thread) cleared up 6+ weeks ago. After checking everything (plugs, coil pack, injector) numerous times I discovered the driver's side fuel injector wiring harness was defective. This is why the CPU went crazy after everything was back together for the new valve cover gaskets. For the valve covers I moved any wiring out of the way as much as possible, and this included some of the injector harness. However, I’m very suspect this was an issue in the past with a previous owner. The wiring plug retention clip for the injector was already broke. More so, the #1 injector was actually seeping fuel through the fuel rail O-ring. Meaning somebody had removed the injector(before I eventually did) in the past and pinched the rubber O-ring upon reassembly.


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