For the last several months I have had this annoying problem and it's not consistent.

when my 2000 ES300 is cold (100k miles) - it starts immediately and idles/runs fantastic. But if I shut the car off after it is fully warmed up and then start it again, the engine will chug/idle poorly and lately is throwing off engine code misfires for bank 1. But they clear up. If I keep running the engine for another 5 minutes or so (engine cools back to running temperature), the engine starts to run fine.

I have replaced most of the sensors such as VVT (both brand new - no change, oil screen is very clean too). Mass air flow sensor, etc. all good.

Car runs great cold - warms up - still runs o.k., but if I shut off the engine so it is hot when I re-start it a few minutes later - misfire codes and rough engine.

Could it be a coil pack failing? (but not failed)
Is there any way to test a coil pak? of course, cold it's probably working
perhaps its oil leaking into the spark plug tube .... I'll have to check. The valve covers are leaky.

 

 

Update -

I checked all three cylinders on bank one - coil paks are dry (no oil in tube) and the plugs look great. I re-arranged the coil paks moving cylinder one to three
just to check if I get a different engine code. I also filled the tank with mid-level Octane gas with 360 sta-bill to 3/4 tank.

I ran the starting cold - took to highway speed for a bit to get engine good and hot - shut it off to "heat soak" and car re-started just fine. Did this a few times
but then on my return home - in the driveway while idling hot - the check engine light pops on and then goes off. Checking the code and the same damn thing - Random cylinder misfire bank one (1,3,5). Engine sounded fine though - unlike yesterday when it idled very rough and engine light stayed on.

I'm puzzled what could be causing this. Plugs are NGK Iridium changed 10,000 miles ago (routine) and coil paks are less than 30,000 miles old.

 

If you are certain the coils are good then move on to injectors. I'm assuming you used genuine VVT solenoids.

 

It is very common that plugs or coils work cold then fail when warm. It will be intermittent at first and get worse sometimes.

Put the old plugs in and see what happens, then put the old coils in and see what happens. This is why we keep old parts, especially electrical and ignition ones.

 

I replaced the VVT solenoids - no change - old ones were good also (no sludge worked very well).

I'm wondering if it could be the camshaft or crankshaft sensor?
The problem is intermittent on bank one and only when the engine is heat soaked (as parking the car for 5 minutes or so when running into a store after a 20 minute drive to get there).

Do camshaft / crankshaft sensors go bad like this (while not throwing off any engine code for the part)?
(how many cam/crank sensors are there I would assume two cam shaft for bank one and two and one for the crankshaft. I can't see them easily, not sure if I am looking at the correct part)

 

 

I will .... need to buy some freeze spray.

(car threw off a P1130 code, but then went away. Probably not the sensor - just the fuel mixture not being right/ misfires. We'll see what the freeze does)

 

Per Tech, if it gets worse when it warms up it's not good. Check for leak (spray something flammable) it engine revs it found a way into the sealed system.
Compression check it cold fine but warm worse something has expanded and changed things.
Good Luck await your test results.

 

Sounds like the same heat soak issue that I have in my Jeep 4.0. Excessive heat vaporizes fuel in the injector(s).

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