Rotating misfires with 5 constant (1 Viewer)

[DubYoda]

99 Landcruiser 100 Series 4.7 335,000 on original motor.

I just had a terrible weekend mixed into an awesome one. My son graduating college headed to Med school with full scholarship.

We drove the LC from Colorado to Utah where he'll be going to U of U med school. 2 hours from our destination check engine like pops on and I lose power and anything under 2200 RPM is rough. I pull off the freeway, plug in the OBD reader (I just happen to have brought with me since we felt a little rough idle but no CEL). #5 & #6 random misfire code P305 and 6.

I pulled and replaced all plugs and coil packs. Plugs in 3, 5 and 7 were 3 thread rings longer that the rest. #5 was in tight as all get out like it was cross threaded. The hook, pin and first row of threads were gone.

After replacing everything with dielectric grease and anti-seize on the threads on start up I got misfire codes on #5 (and ever after) 3,4 and 8. Then I cleared the codes and got #5 2,1. I swapped in an old coil pack and got #5, 8 and 7. Then I switched coil pack 1 for 5 back to all new coil packs and the only code I got thereafter was from 5 until about 1 hour from home and 7 came back on (yeah I drove it all the way home with 5 coding - broke is as broke gotta do).

What do I need to look for for the rotating misfires? Is there a relay?

What could have nuked the tip on the #5 plug? The longer plug would seem a bad thing but the other 2 were not damaged like the cylinder hit it? The new plug threaded in flawless and snugged right up like it should which further confused me. I have owned and do own many aircooled VW's so I'm familiar with plug thread issues, heli-coils and time-serts.

I have this burnt valve thought along with an alternate idea of a cracked piston with a chunk getting flung into the plug then it arcing like crazy until the coil was burned up...but #6 was coding at the same time.

Anyway I'm all ears and looking to save my baby, we have love this car like no other and do not want to give it up. I'm already mentally preparing for possible motor swap.

I have kept up on all maintenance and oil changes and 250,000 of the miles are from me and my family. I'll post the plug pics in a response since I wrote this on a computer and pics are on my cell.

TIA

 

[DubYoda]

regular plug, blown plug and extra long non-blown plug

 

[DubYoda]

Alt view 1 of regular plug, blown plug and extra long non-blown plug

 

[DubYoda]

Alt view 2 of regular plug, blown plug and extra long non-blown plug

 

[DubYoda]

Alt view 3 of regular plug, blown plug and extra long non-blown plug

 

[outdoorsman]

My first thought is do a compression check. Maybe low compression is causing that?

I had the same codes a long time ago and turn out to be a spark plug was loose and ready pop out. It sounds like you have already ruled that out.

Could be a wire harness issue / bad connection.

When is the last time the timing belt was changed?

 

[2001LC]

So to just say "X" is why you've a random miss-fire, is not realistic without more info.

Looking your pictures of plugs and your statement "little rough idle before trip" ... States to me: minimally and improperly maintained engine. Picture also show a mix of spark plugs types and manufacturers. The only spark plug number I can see is not spec for your engine. I know you said you've kept all PM, but was that by the book (every ~5k miles) and with what products (parts).

I've be seeing spark plugs walking off, more so on inners (3, 5, 4, 6). As they loosen combustion gasses escape, which carbon up threads. This makes hard to come off.

Wide gaps of spark plugs which happens with use, draw more current which can damage plugs. This extra draw overheats coils, heat is the enemy of coils. A loose spark will drawing more current also. Staining up to boot line of spark plug(s) indicates some loose spark plugs for one thing. Your plugs are wet from unburnt gas and oil. This may be due to bad firing or not firing, along with improper operation of PCV system. Improperly functioning PCV system can increase crankcase pressure blowing oil past rings and valve guilds. Head covers should be torqued to spec to stop leaks. Or replace head cover gasket and spark plug tube seals, if torquing does not stop leak.

I agree a compression test ie in order. As long term improper PM can damage even these million mile engines. They do not use oil or smoke, if proper PM is done every ~5k miles.

Few things to also consider are the parts you used. Dense coils that are direct replacement according to Toyota parts numbers are best. Many fake Denso & NGK on ebay coming from China, these are junk. Many aftermarkets are junk as well.

Spark plugs should be either Denso or NGk Iridium Toyota spec PN # not both.

PCV should be in good working order and entire engine vacuum system should be without leaks. This is especially true of grommet and both LH & RH hoses of PCV.

History of engine is also important i. e. Interval and type of: Oil & filter change, air filter, fuel filter, quality of gasoline, fuel cleanser like 44K added to gas tank, condition of fuel injectors & FPR, T-body & MAF cleaning. All these things and more in perfect working order through engine's history makes difference on condition of rings, cylinder walls, valve's seat/guides/seals.

Coolant system health and overheating is another area that needs addressing.

 

[abuck99]

How many miles since the last plug change? Guessing 10’s of Thousands of miles of incorrect plug application have taken its toll on your motor, coils etc.

That middle plug doesnt speak well of the condition of the top of the piston. You may want to get that scoped to see how much damage in there.

Who’s been doing the maintenance?

1. From the photos posted you are running the wrong Denso plug application for a 2UZFe V8. The FK20HR-11 is for a V6 avalon-camry motor.

2. Oddball NGK thrown into the mix,

Correct plug would be Denso SK20R11

Get some new correct plugs
Denso OE Identical Automotive Replacement Parts on DensoProducts.com
, have your cylinder scoped to see if any damage, test the coils, say a prayer.

 

[DubYoda]

I appreciate the things to look for. I'm not going to match wits with some of you guys who clearly have been more maintenance disciplined than I have. I know my lapses have created my issues and I'm trying to determine my next steps. I know I need a few slugs to the arm for being lax so I'll take it, just looking for advice after the condemnation is the reason for the post.

Timing belt is due in 2500 miles, but...

 

[2001LC]

Sorry, Hidden in my rant;

Once Compression checks out ok, then:

Major tune up done by the book.

"Few things to also consider are the parts you used. Dense coils that are direct replacement according to Toyota parts numbers are best. Many fake Denso & NGK on ebay coming from China, these are junk. Many aftermarkets are junk as well. Spark plugs should be either Denso or NGk Iridium Toyota spec PN # not both.

PCV should be in good working order and entire engine vacuum system should be without leaks. This is especially true of grommet and both LH & RH hoses of PCV.

Oil & filter change, air filter, fuel filter, quality of gasoline, fuel cleanser like 44K added to gas tank, condition of fuel injectors & FPR, T-body & MAF cleaning. All these things and more in perfect working order through engine's history makes difference on condition of rings, cylinder walls, valve's seat/guides/seals.

Coolant system health and overheating is another area that needs addressing."