bige84

Diagnostic tool reads all 6 cylinder misfire Lexus RX 350

Lexus RX 350
2007
225k Miles
My wife owned this car before we got married, and I believe purchased it new. I cannot verify if the spark plugs have ever been changed.

Hey I got a rather urgent car question for you. Check engine light comes on started a month ago as car shakes.

Didn’t think too much of it. Auto shop says needs new coil packs and spark plugs quoted $1,200!

Symptoms got worse when idle or under a load of 75 mph ...hooked up to reader w a buddy at work so it’s a 6 cylinder misfire diagnostics read was consistent w auto shop. The battery / alternator test out good. I changed just the first 3 easier spark plugs in front yesterday myself in effort to save money in Cylinders 2,4, and 6. But I didn’t change out the coil packs.

Thought this would buy me time but apparently car is progressively worse and check engine light that flashed on Tuesday is now flashing again on Thursday w worse symptoms. Any thoughts?

Midday update:
Just reran the diagnostic tool w a buddy’s tool. It's now only showing
OBD II P0354 Ignition Coil "D" Circuit Malfunction

Any additional thoughts on this?

Drove my car home and car had flashing Heck engine light and I could feel the shaking and vibration.

Evening update:
Check engine light was flashing on the way home. Went to O’reilys Auto. Guy there reran The diagnostic test. And confirmed the current misfire is ignition coil D. So I moved the fourth cylinders existing coil pack over to the second cylinder’s slot. Then moved the second cylinder’s existing coil pack in the open spot which is the fourth cylinder’s spot. We ran the diagnostic test and it still said ignition coil D. Then he did a hard reset and erased all of the history. We ran the test and there were no misfires. Then he started the car and pumped the gas multiple times and the check engine light did NOT come on. So then I drove it for 3 miles and it still hasn’t come on. The mechanic seems to think that the computer was misreading the my car and therefore adapting the fuel and air ratio thus giving me problems on the way to work this morning. Is this plausible.

What’s my next step?

Next Day Commute

I drove to work this morning and the check engine light came back on but was not flashing until I got about a mile out from work.

Removed spark plugs....

Nad1370

Hello and welcome to CL

P0354 is usually a failing ign coil pack.
But if i read your post right, you said you replaced the 3 front coil packs already.
Is that right?
What brand coil packs?

So when you swapped coil packs 2 and 4 -- what code did you get again?
Which cylinder had the misfire after swapping packs?
You should reset/clear the check engine light every time you swap coil packs or you'll have your original code still stored.
Lets start with this first before moving on to other possibilities.

matts6887

Those plugs look really coated and possibly a bit carboned or fouled. Yea the computer must have altered the mixtures during the time the cel was flashing. That’s my guess.

bige84

Does it sound like the computer was still mis reading their issue?

bige84

I hadn’t considered that as an possibility. What would you do as a next step if you were in my shoes?

Nad1370

It threw a P0354 which is a – Ignition Coil “D” Primary / Secondary Circuit
This is not a spark plug problem.

A P0304 though is possibly a spark plug problem.

bige84

My wife owned this car before we got married, and I believe purchased it new. I cannot verify if the spark plugs have ever been changed. It's an 2007 Lexus Rx 350 with 225k miles on it.

Margate330

Hi bige, since you do not know the service history and with a misfire on all cylinders(not good) and the mileage- purchasing a proper scanner
for your vehicle can be some of the best money you ever spent.

At that mileage you can be dealing with multiple issues and throwing $1,200 at it may not give your desired results.
PS- Your light blue font barely shows on my monitor.

>> Recommend a scanner that can read & clear codes and read fuel trims, maf, A/F, O2, air and coolant temps, ignition timing, etc, etc and post them.

Audiqv8

Flashing check engine light is not good. It means to stop driving before you do any more damage to your car. Since you already know that the coil(s) are bad then fix it before you break something else like your ECU. If the coil is shorted it can ruin the drivers in the ECU which will require a new ECU. If the ECU is pumping fuel into the system this can ruin your cats which will cost more than the car is worth to replace.

matts6887

well I would at least try replacing the front 3 plugs and possibly the coil packs as well to see if that does anything; if not u might have to go through the agony and pain of getting the rear ones outta there to see what they look like as far as the plugs go. If the cel is no longer flashing then it’s possible the computer might have cleared itself somehow. Yes the plugs in the rear are a pita!!! But u might have to tackle that job if it means getting to the bottom of the issue possibly

Felix

Like mentioned above, need to swap out the plugs & coils. It does have 225K on it after all. If your going to do it, I'd swap all the plugs/coils.