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Discussion Starter #1
I recently started my truck (2000 4.7) yesterday and found that it didnt feel right. it started to shake. it was very noticable. i put it in drive to see if it would go away but it became worse and the check engine light started to blink. pulled it back into the driveway and had a buddy come over to see which code it was throwing. P0300(MCMIS)/P0303(cy 3)/P0306(cy 6)/P0171(fuel too lean Bank 1). So i began to switch out the bad coil packs to double check it was throwing those. when doing this i noticed a clicking noise that I had never noticed before. My buddy said that it could mean my valves need adjusting. the truck has 160,000 miles on it. i bought it used and dont believe its had any adjusment done to it. I had this problem happen before when driving on the freeway. And it turned out to be a bad coil pack. that was about three years ago. just wondering anyones thoughts on this. should i replace all the coils or spark plugs? not really sure how to diagnois to see if it is the valves or not.

Thanks!
 

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Discussion Starter #3
the codes kinda were jumpin around. at first it said on cylinder 3 & 6 but when we swtiched with another it said the 1st cylinder was the problem. we never touched the 1st cylinder. the plugs looked good. no black carbon residue or anything. i thought this was gonna be a simple fix but now that this knocking noise started i dunno now. how would a mechanic at a shop tell me which one it is?
 

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2015 Toyota Tundra DC SR5 5.7L
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The same way you're trying to diagnose it: swapping the coils around and seeing if the fault code follows the coil. If it does, it's the coil. If it doesn't, then it could be spark plug(s), the harness, even a fuel-air sensor.

I would clean the MAF, clean the throttle body, replace the air filter (if needed), inspect every spark plug for fouling, fill the tank with clean gas and add a bottle of Techron to it, clear the codes, then see if it comes back.
 

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another thing to make sure other than Remmy recommendation is your spark plug brand is NGK or ND (Nippon Denso) not the other brand.
 

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How long was your truck sitting before you started it and found this problem?

The ECM diagnoses misfires indirectly, by continuously monitoring the angular acceleration of the crankshaft via the crank position sensor.

So, misfire codes can be set by ignition problems or by fueling problems and also by mechanical problems.

Without listening to your engine it's impossible to say what the clicking sound is, but the fuel injectors on the 2UZ-FE can make a clicking sound that can be mistaken for valve noise.

The 2UZ-FE has solid lifters with solid shims so the valve clearances have to be checked with a feeler gauge and adjusted by replacing shims as necessary - see attachment. It's said there's rarely a problem with valve clearances on these engines even after 200,000 miles but it's something to keep in mind.

The fact that you have multiple misfire codes that are jumping around suggests you may have a fueling problem. If this were my truck I'd be thinking about replacing the fuel filter and disassembling the fuel rails to inspect for dirt the stainless steel mesh catch baskets in the tops of the fuel injectors. After that I might replace the fuel pump.

Also, other people with multiple misfire codes have found: (1) water in the fuel tank from a leaking fuel pump tank gasket; (2) bad/plugged cats; (3) wiring chewed off the knock sensors by rodents; (4) replacing the spark plugs fixed the problem. There's also a small chance that your crank position sensor is failing.

Do the cheap/easy stuff first. Fresh fuel with a bottle of Techron and a bottle of dry gas.

View attachment Valve Clearance Inspection & Adjustment.pdf
 

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Discussion Starter #7
thanks for all the responses! so yesterday I replaced all of the spark plugs and replaced the coil pack over cylinder 4. It started just fine and I could not hear any knocking or clicking noise. I didnt feel any shaking at all that i had before. took it out and drove about 2 miles. im waiting today to see if my buddy can bring the reader back over to see if it is throwing any more codes. he still suggests that i take it to a mechanic and get the valves adjusted. i baby this truck and drive to school everyday so i dont think the probelm is chewed wires or anything. but i will try the fresh gas idea and clean air filter
 

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hard to tell from the angle, but $50 for some iridiums are a cheap price to pay for 75-100k miles.
Iridiums are a waste of $$$ on the non-VVTi engines. Trust me. I ran 'em. No difference.

The best bang for your buck is the damn Densos the dealer carries or the NGK Platinum BKR6EGP plugs. Both are under $3 each. They're so cheap, I'm running my plugs on a 20,000-25,000 mile interval. I can do a complete swap in 30 minutes. It's a no-brainer.
 

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that gap was over .25 these plugs had never been replaced. they were still stock.
Did you measure that gap at over 1/4 inch? Seems unlikely. The electrode erosion rate for a copper spark plug of the correct heat range is about .010" per 40,000 miles, so I'd expect to see a gap of about .072" on stock plugs run for 160,000 miles.

How long have you had this truck? I have a pretty long checklist that I work through on a used vehicle and "inspect spark plugs" is close to the top of the list.

Remmy's right, also. The best plugs for these engines are the $3 Denso copper plugs specified by Toyota - K20R-U for your truck.

View attachment Toyota Spark Plugs 2011.pdf
 
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