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Old 12-28-2019, 11:40 AM
 
1,765 posts, read 4,337,181 times
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I have a 2002 Toyota Highlander. A few weeks ago the Check Engine Light came on (I never ignore it) and I had it checked, it was code PO 304, cyl 4 misfire. I wound up getting one new ignition coil and 4 spark plugs (also got oil/filter change) for $500 total repair. (Car does not have 110K miles yet, have owned it 11 years.)

The next week the CEL came on again -- took it in to read code -- the same one. I left car for day and they checked it all out again, other coils ok, mechanic drove it around half-hour- CEL did not come on again.
About another week/50 miles later, CEL comes on again Christmas Eve. Took it back yesterday just to read code -- same one. They asked me to bring it back Monday and leave it again. I asked if they can't at least delete the repeating code ...they said they have some $5,000 machine that has to run for an hour that checks everything, whatever that is. I am tired of worrying about the CEL light...as mentioned, I don't like to ignore. I am aware it could be "gas cap loose" (happened several times) or something far more serious. This could wind up being one of the other coils. My worst nightmare is just having my car die on me in traffic, as it did several years back when the alternator went.


I am wondering if these guys know what they're doing or I should get a second opinion somewhere else and at least see if they get the same code?? I've been going to this shop for years (essentially 3-store tire chain with repair shop...but personnel change a lot) and I like to think they are straight with me and don't upsell when I don't need something... I just am having the sense they really don't know what's wrong.

Any thoughts? Thanks!
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Old 12-28-2019, 02:46 PM
 
Location: East of Seattle since 1992, 615' Elevation, Zone 8b - originally from SF Bay Area
44,291 posts, read 80,538,426 times
Reputation: 57243
I had the same issue on a 1996 Explorer V6, and it turned out to be a cracked head. It was a very small crack and at about 70,000 miles was just barely starting to allow coolant into the combustion chamber. About 2,000 to repair, back in 2003, though I managed to get it down to $600 with a lot of negotiation and threats since I had just bought it used from the dealer a month before. Of course, your problem may not be the same, just giving this as an example of the many causes of a misfire.
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Old 12-28-2019, 03:31 PM
 
Location: Iowa
865 posts, read 621,210 times
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"I am wondering if these guys know what they're doing"

You didn't mention who "these guys" are, I'm assuming the dealer.

I've found that Toyota dealer service must be where rookie mechanics go to train. The times my wife has sent her Camry to the dealership for service, they just want to "throw parts" at the problem...money for them.

Take it to an independent mechanic. They tend to be more frank and truthful.
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Old 12-28-2019, 04:10 PM
 
Location: NW Indiana
44,299 posts, read 19,967,508 times
Reputation: 115119
Quote:
Originally Posted by Robeaux View Post
"I am wondering if these guys know what they're doing"

You didn't mention who "these guys" are, I'm assuming the dealer.

I've found that Toyota dealer service must be where rookie mechanics go to train. The times my wife has sent her Camry to the dealership for service, they just want to "throw parts" at the problem...money for them.

Take it to an independent mechanic. They tend to be more frank and truthful.
OP stated "they" are people at a tire chain store which includes a repair shop.

To the OP, I'd definitely get a second opinion. Unfortunately, most places charge a diagnostic fee, but it seems you need a fresh set of eyes to look into the problem.

.
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Old 12-28-2019, 04:24 PM
 
8,272 posts, read 10,917,070 times
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Quote:
Originally Posted by Robeaux View Post
"I am wondering if these guys know what they're doing"

You didn't mention who "these guys" are, I'm assuming the dealer.
I think OP stated shop and not dealer.

"Fixing P0304 should be considered a high priority. Unlike a lot of the OBDII codes, this code has to do directly with engine combustion. It also can cost money to ignore it, since driving with a misfire can damage the vehicle’s catalytic converter. The engine is also not firing all of the fuel, so raw fuel is also passing through Cylinder 4 into the exhaust. Mileage may suffer as well when your Highlander has P0304 as well."

LINK

Take to the Toyota dealer. Ask to diagnose and estimate. Do not authorize any repairs until you find out what is the issue. Do not drop off and leave. Be a "wait" customer.
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Old 12-29-2019, 08:03 AM
 
Location: Watervliet, NY
6,915 posts, read 3,915,024 times
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Is the repair guaranteed/warranted? If so, keep taking your car back to the same place and make them keep doing fixes, fixes which you WON'T have to pay for since you already paid once for them to fix the problem.

I had a similar coding issue a year ago (P0442) but, since I read the fine print in my original bill receipt that said the repair was guaranteed for 12 months, I kept going back and making them redo the work until they got it right.
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Old 12-29-2019, 10:13 AM
 
586 posts, read 311,489 times
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My son-in-law had the same issue on a 2005 Corolla. It was caused by a barely visible crack in the intake manifold gasket. There was a TSB (Technical Service Bulletin) from Toyota on it.
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Old 12-29-2019, 06:56 PM
 
22,619 posts, read 24,456,098 times
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Cylinder problem or something involving the cylinder.........valves, fuel-delivery.
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Old 12-29-2019, 07:40 PM
 
1,765 posts, read 4,337,181 times
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Quote:
Originally Posted by ContraPagan View Post
Is the repair guaranteed/warranted? If so, keep taking your car back to the same place and make them keep doing fixes, fixes which you WON'T have to pay for since you already paid once for them to fix the problem.

I had a similar coding issue a year ago (P0442) but, since I read the fine print in my original bill receipt that said the repair was guaranteed for 12 months, I kept going back and making them redo the work until they got it right.



That's essentially what I am doing, as they do guarantee their work for 3 years or 30K miles.



I was thinking at least if an AutoZone or similar shop would come out and check the code and get the same one... it's just frustrating because I do leave the car for the day then am fairly stranded. They do drop me off and pick me up though. I like to think they want to resolve this too and stop seeing me. They aren't making any new money doing this.



I bought the car used so never dealt with a Toyota dealer.
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Old 12-29-2019, 09:48 PM
 
2,486 posts, read 1,396,438 times
Reputation: 3112
Does your car have to past a yearly emissions test? If not DONT WORRY ABOUT THE CEL LIGHT BEING OWN. You need to understand a little more about the OBD11 system on your car and you will know why I said that.
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