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Discussion Starter #1
I'm about to inherit my wife's 2007 Rav4 Limited V6 with 178,000 miles on the odometer. I plan to drive this car for another 2-3 years (hopefully) and want to do some "tune up" work to get it driving smoothly again.

We've been pretty diligent in the maintenance of the vehicle, but I just realized the other night that we never had the spark plugs changed. Some recent issues with starting the vehicle, a rougher sounding engine noise and significantly reduced fuel economy have me thinking the spark plugs and/or ignition coils could be part of the problem. The mechanic that just replaced the alternator at $750 didn't think to ask about any of these items.

If a plug or coil were bad and causing a cylinder to misfire, wouldn't this trigger the check engine light to come on? The only time we've noticed the CEL is when we're due for an oil change. I plan to go ahead and change all 6 spark plugs due to the mileage, but I'm wondering if it's worth the expense to replace at 6 coils while I'm doing the plugs.
 

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From my understanding if a coil is bad you will have a check engine light showing. It's not inexpensive to replace both plugs & coils so that's your call. The rear plugs are a bear to get to and you might not want to go back in there again to replace a bad coil.
 

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usually bad fuel economy and rough idling can also be caused by bad o2 sensors, and those are known not to cause a check engine light until they are really bad.

could also be a catalytic converter that is blocked and causing restriction.
 

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coils rarely go bad. just unplug the coil and pull it out to inspect it for abnormal wear like cracks or burn marks. replace as needed. replace with oem denso spark plugs. i would clean the maf with maf cleaner spray and put a new engine air filter and cabin filter too. put some techron additive into the gas tank to "clean" the injectors.
 

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If your RAV has 178K on the original spark plugs, stop speculating on this or that. Get the plugs changed then see. Not sure how these things are set up but typical it is hour job at the most.
 

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coils rarely go bad. just unplug the coil and pull it out to inspect it for abnormal wear like cracks or burn marks. replace as needed. replace with oem denso spark plugs. i would clean the maf with maf cleaner spray and put a new engine air filter and cabin filter too. put some techron additive into the gas tank to "clean" the injectors.
The 2006, 2007, and 2008 coils went bad on a regular basis. The mother ship bought a bad batch, there are tons of problems on this forum from the coils from that era. Fortunately our cars have not suffered from this malady yet. The water pump is also a possibility for replacement. I would most certainly replace it along with the belts and thermostat.
 

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The 2007 and 2008 coils went bad on a regular basis. The mother ship bought a bad batch, there are tons of problems on this forum from the coils from that era. Fortunately our cars have not suffered from this malady yet. The water pump is also a possibility for replacement. I would most certainly replace it.
It was the 2006 and early 2007's that had the coil problems. It's rare to hear of a coil failure on 2008 and later.
 

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If your RAV has 178K on the original spark plugs, stop speculating on this or that. Get the plugs changed then see. Not sure how these things are set up but typical it is hour job at the most.

On a 4 cylinder, yes. On a V6 plan on at least double that since the plenum needs to be removed to gain access to the rear spark plugs.
 

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I'm glad to know I was wrong but early 2008 models built in '07 may indeed have the coil problem.
 

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When your RAV is due for an oil change, the "maintenance required" light will come on, not the Malfunction Indicator Light (MIL)


I would replace the spark plugs (DENSO Iridium ONLY) and install 3 new DENSO ignition coils on the rear bank. Keep the old coils if/when one of the front coils fails.
The latch on the connector for the ignition coil is delicate and will crack if looked at wrong. Be prepared to replace any broken connector shells. Heat hardens the plastic so it won't flex when the latch is depressed. I've seen zip ties to hold the connector to the coil, which will work, but the right way would be to replace the connector shell. The wires can be removed and installed in the new connector shell, which saves soldering.


I have replaced ignition coils on newer Avalons and V6 Camrys and Siennas. If the coil was made by Diamond, it will fail. DENSO did not make this coil until recently.


As for the mechanic not recommending this service, I would have done the same thing. When a customer has a big bill, they don't want to hear they need to spend even more money. People think my profession is out to get every dollar in your pocket. Not understanding how things work makes it even harder to accept that the tech is not ripping you off.
 

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Discussion Starter #11
usually bad fuel economy and rough idling can also be caused by bad o2 sensors, and those are known not to cause a check engine light until they are really bad.
My aviation mechanic buddy mentioned the same thing about the possibility of a bad O2 sensor. However, without a CEL, how would I know which sensors to replace? Seems like this could get pricey if I just start replacing everything that could be causing my issues.
 

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It was the 2006 and early 2007's that had the coil problems. It's rare to hear of a coil failure on 2008 and later.
Agreed. From everything I've seen on the forum that is correct.

On the O2 sensors my comment is why not first fix what you know is wrong, the spark plugs? At 178K there can't be much left of them!

Two thoughts on the coils. If they haven't failed in 178K they probably won't. But since they have to come out anyway replacing the rear ones makes sense as long as you aren't paying $100+ for new ones.

When my coils failed I got a MIL (CEL) immediately accompanied by rough running and power loss. Resetting the misfire codes to turn off the MIL was a temporary cure.
 

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My aviation mechanic buddy mentioned the same thing about the possibility of a bad O2 sensor. However, without a CEL, how would I know which sensors to replace? Seems like this could get pricey if I just start replacing everything that could be causing my issues.
I hear you about the price of replacing all that stuff, but look at it this way, it's a lot cheap than a new car payment ;)

On my old car, the first o2 sensor was to set the air fuel ratio, and the second one was to confirm the converter was working. I would start with the first one. I'm not even sure the rav4 only has 2 sensors... someone knows of the top of their head?
 
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