99 RX-300 Ignition Coil Failure

The check engine light came on yesterday on my wife's 99 RX-300, and the engine was missing badly. It happened all of a sudden; had been running
perfectly until then. I took the car to the nearest Toyota dealer, hoping to get it fixed quickly and inexpensively as opposed to a Lexus dealer, which is farther away, and requires an appointment. I don't have a code reader, so I couldn't determine what the problem might be ahead of time.
They quickly diagnosed a failed ignition coil on Cylinder #1, but also said that all the spark plugs we fouled, and the engine required a carbon-cleaning procedure that cost $200, in addition to the $300 to replace the coil and all six Iridium spark plugs.
The car has only 65K miles on it, and has been maintain by the book. It is out of warranty, because of it's age. We bought it CPO with 24k mi. on it in May 2002. The original service date was 4/23/99.
Question: Was it really necessary to replace all six plugs? Spark plug replacement isn't called for until 90k mi. according to the Lexus maintenance schedule. Also, was the expensive carbon-cleaning procedure really necessary? Why would all the plugs be fouled after only 65k mi.?
Dealer's Answer: The plugs needed changing because of the age of the car, not mileage. The carbon cleaning was necessary because of the use of inferior gasoline containing 10% ethanol. The car is used only for short trips, therefore never gets combustion chambers clean.
I add a bottle of Techron every four months, when I change the synthetic oil and filter.. We only use name-brand regular grade gasoline. The car is only driven about 6-8K per year. Did I over-spend for this service, or is the dealer correct in his assessment?
Another maintenance item on the 90K service is the timing belt. Should I also have this changed right away, or should it last until the car reaches 90k mi.?
Thanks for your opinions!
--
Stephen Clark
99 Lexus RX-300
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I have a 2000 ES300, with a similar age and six cylinder engine. I also had one coil suddenly go bad. The Pep Boys shop replaced the coil, the ONE spark plug, and gave the engine a fuel system cleaning. The car then ran fine. So I got off cheaper than you did.
I am not a car mechanic, but I think a thing to try would have been to replace the coil and one plug, and take it for a test drive. They should have offered to show you the used spark plugs. It sounds like even Toyota shops act like most shops, trying to justify extra repair work, no matter the problem.
Even though age might be somewhat of an extra factor in replacing the timing belt, I think you can be safe in waiting to 90,000 to 100,000 miles before they change that. That might cost in the rough ballpark of $1,000, because thay also (correctly) take that opportunity to change the water pump and coolant, while many parts are already off the engine. And there are timing belt tensioners which will probably need replacement at that time. And that may be the normal mileage for a first time ever spark plug replacement, but tell them you replaced them at 65K, and to only check them first.

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Next time, you can borrow code readers from some auto parts stores like AutoZone. The code was probably related to misfires.

It is usually a good idea to replace spark plugs in sets, especially if all of the spark plugs were fouled. The spark plugs may have been fouled due to the numerous short trips where the engine doesn't get hot enough to burn off the carbon that accumulates when the engine is running rich when warming up.

Carbon cleaning services do work. Without seeing the combustion chamber and spark plugs, it is difficult to determine whether your car needed one or not.
Techron is a fuel injector cleaner and is not designed to clean carbon from the combustion chamber. Over-use of fuel injector cleaner can cause problems because it acts like something caustic. I recommend that you discontinue the routine use of Techron and use it only if you are experiencing driveability problems, or if it makes you feel better, once every year or two is more than enough.
To prevent future carbon build-ups, take the car on a highway trip once in a while, the longer the better.

Rubber loses it pliability over time, which is one of the reasons that the timing belt replacement has a time and mileage replacement interval. Your RX is now 9 years old, going on 10, so in terms of time, you have already gone 150% of the recommended time interval. The RX engine is an interference engine, which means that engine damage will probably result if the timing belt breaks. You are already on borrowed time, and at the rate the car is being driven, it may beanother 3 years before it reaches 90,000 miles. It would be safer to replace it now.
--

Ray O
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Thanks very much to both of you for your kind replies and comments.
Looks like I need to perform all services called for at the 90k mi.or six year schedule.
I just don't drive the vehicle myself very much, so it didn't occur to me that major services are going to come late if I go strictly by mileage, since she drives the car only for local errands, and back-and-forth 1.0 mile to school, where she works. We do take it out of town two or three times a year, but only to Austin and back to visit our son, a 350-mile day trip.
BTW, have noticed since the service at the Toyota dealer. I'm seeing 3-4 mpg better average around town. So I guess it did need the full treatment, and it will save some gas expense over time.
Ray O, thanks for your sage advice about the timing belt, and the Techron. The dealer told me exactly the same thing about using Techron; he too said it was caustic. And, I have not changed any belts or hoses, so I guess all those need to be replaced as a preventative measure. What is the useful life of the serpentine belt?
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Stephen Clark
99 Lexus RX-300
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If you drive a longer distance than your wife, it might be worth it to trade vehicles once in a while to reduce the carbon buildup and let the engine warm up to operating temperature. This would also help the moisture that accumulates in the engine crankcase and exhaust to evaporate and prolong the life of the engine, exhaust system, O2 sensors, and catalytic converter.
Another problem with frequent use of Techron in your case is that it sits in the fuel system for such a long time that it can start deteriorating the fuel system components. Fuel injector cleaner additives should be used as fast as possible, preferably within a week at the most.
The useful life of accessory drive belts, sometimes referred to as serpentine belts, is roughly the same as the timing belt, and should be changed when the timing belt is changed. Since the belts need to be removed to replace the timing belt, it is a matter of the cost of the belts and doesn't require any extra labor time or charges.
Hoses last a lot longer since they are not subjected to the stresses of driving a pump, compressor, or alternator. Hoses should be inspected once a year for deterioration like cracks, swelling, collapsing, etc. but otherwise don't need to be replaced as a part of a periodic maintenance. If you look at the maintenance recommendations in your owner's manual, you'll note that there is no interval for replacing hoses, just inspection.
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Ray O
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The dispersant in Chevron's Techron is polyether amines (PEA). It's an advanced class of ashless dispersant and not a solvent. So if you use top tier gasoline (www.toptiergas.com) then you should have less of these deposit related problems. However with aftermarket bottles you'll find some solvents in there too. It's the solvents that attack the rubber components that's why these cleaners shouldn't be used too often. But I'd say every 30K should be fine unless you have a problem engine.
It's a good thing that the dealer switch you over to the newer Iridium spark plugs. These burn cleaner and stay cleaner than the old platinums.
http://www.ngksparkplugs.com/products/spark_plugs/laser_iridium.asp?mode=nml

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Stephen Clark writes:

Wow, they are really up-selling you. Don't be a sucker.
I doubt your plugs are fouled or that you have a carbon problem.
The coil is about $110 at NAPA, and a medium do-it-yourself install on the 1-3-5 cylinders reaching under the air intake. The 2-4-6 cylinders are a 5-minute easy job.
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