MellonC00

Has anyone experienced something similar?

The other day, I heard my engine knocking going up hill with full load. It happened about three times in about 3 days. A day after, my check engine light came on.

Do you think these two are related problems? The knocking went away with a new tank of gas but the check engine light stayed on until my mechanic reset the sensor.

Questions?
1. Why does a Lexus engine knock? I've never heard any knokcing from any cars I've driven before.
2. If the mixtures of O2 and fuel got messed up during knocking but were fixed after putting in a new tank of 91 octane gas, why does my check engine light stay on?
3. Is this something that is covered under the powertrain warranty (my standard warranty expired)?
4. What is the likelyhood that I may have demaged valves? or need a new header?

Thank you for your input.

Lexmexico

Can you get the actual OBDII code from us, it would really help as a lot of us have the service manuals and could assist you better.

MellonC00

Unfortunately I don't have the OBDII code.

salimshah

There are too many reasons for the engine to knock, but it should not. Here are two things you can do at home.

With the engine COLD check coolant level in the radiator tank as well as the overflow reservoir. Fill if required.
Use the right octane, good quality gas.

For others, you need the OBD.

If it is the Oxygen Sensor, you may be covered under emissions warranty.

Salim

Lexmexico

A couple of things:

1) Sparkplugs need changing (possible but unlikely)

2) Clogged injectors. Plenty of cars knock and ping here in Mexico City due to really bad gas, and they sell injector cleaners like no tomorrow here. I personally use Chevron's Techron despite using Premium.

MellonC00

Thank you for the suggestions. I added the coolant last night. As for the Techron stuff, you are the 4th person to tell me that Techron works well. I will definitely give it a try.

Thanks again.

ederny

"did I damage anything?" - Perhaps not, but how does it perform? If all seems normal, then just have fun and drive. However, if you sense any difference in performance, have it checked out by a Lexus, or at least a Toyota mechanic. Be alert to any other change of the same problem reoccurring.

MellonC00

Just a quick update. After and during 2 full tanks of Chevron 91 and 2 bottles of Techron, I haven't heard any knocking. No loss in performance or fuel economy.

Check engine light has also dissapeared.

Thanks all.

aprairie

FWIW, I bought a 99 CPO with 32K miles and had engine knock the day after taking delivery. After several runarounds with the dealer, they diagnosed as engine oil gelling that had caused the engine walls to score.

Yes, running 91 octane made the problem disappear (the dealers orginal fix), but should you have to run 91 octane when the car can handle 87?

I'm still a bit pissed at Lexus because this car has been in for service about 10 times in the 16 months we have owned it. I'm pretty sure it qualifies as a lemon, and I feel like the whole CPO process was a load of crap....especially since the car passed CPO even though the engine oil gelling problem had to have happened with the previous owner. Got a new engine block per the warranty, but I'm sick of taking the car in for service and have everything break down piece by piece.

I would not keep putting 91 into my RX300 if that was the only way to solve the knock. You are taking care of the symptom, and not the problem.

Good luck,
Drew

MellonC00

In about 3 days, I am going back to 87 octane. I really hope that the problem was caused by "bad gas". If the problem occurs again, I am definitely taking it in for service.

I will post an update after going through the 87 octane.

MellonC00

Just came back from a 900 mile trip to San Fran. Following are what happened:

1. Used Chevron 87 the whole time.
2. Check engine light came on immediately after filling up (going uphill)
3. When Cruise control is engaged, transmission won't upshift after down shifting for acceleration. For example, if I went uphill and it down shifted automatically, it won't upshift even after I've crested the hill. Sometimes, it will downshift by itself but the shift is not smooth - feels more like a Dodge than a Lexus.

I think I am going to have to go to the dealer. I hate going to the dealer for anything but in this case, I don't think I have a choice.

Can anyone recommend an honest Lexus authorized repair shop or a Dealer repair shop in the South Bay (So. Cal) area? Thank you.

MellonC00

I took the car to the South Bay lexus today and found that my Mass Air Flow sensor is faulty. I am having this replaced. I will post my remark after going another uphill.

salimshah

OBD would have shown that.

Since it is part of the air/(fuel)/emission, is the dealer covering the repair?

Salim

MellonC00

Lexus America says that none of the O2, MAF or TB sensors are covered unless there is actual and physical damage to the engine or the transmission or any of the emissions related parts (but I thought MAF sensor was a related part?)....

Anyways to make a long story short my dealer trip was somewhat expensive ... I guess it always is the case. The dealer shuttle showed 45 minutes after I dropped my car off, the service advisor flat out said that RX was never part of the engine oil gelling problem... until I actually mentioned the letter that Lexus sent out to the RX owners, kept cutting me off in the middle of my sentences...

My knocking has disappeared but I am hearing something else from the engine now. Around 4000 rpm, in third gear my car makes a tiny screeching or chirpping noise. I don't think it's knocking because the frequency is somewhat constant. I am going to drive it around for a week or so and see what happens.

By the way, the dealer name is South Bay Lexus, Torrance CA. The repair cost about $325.

MellonC00

It's been a week since I replaced the MAF sensor. I am operating with no problems. I am going to assume that the problem was taken care of. Thank you for the helpful remarks.