Replace the engine or just buy a used 4th gen?

[drei4runner29]

Swap coils around to see if misfire follows?
Try a new ECM?
Spark plug wires good?
Misfire all the time or cold....hot...under load.....idle?

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Spark plug wires are good. Just had them recently replaced along w/ the spark plugs.

As far as misfires go during start ups, it's intermittent. Sometimes on a cold start early in the morning, it will misfire and sometimes not. Same goes later on in the day after sitting for several hours. It will sometimes misfire and sometimes not when I start it to go home from work.

 

[drei4runner29]

2005 4Runner I recently bought was having random misfire codes for a while also. End result? Timing chain broke possibly causing valve damage. Do yourself a favor, with your mileage, replace the timing belt set. This one broke at 250K and not a spot of sludge in this engine, it was pretty well taken care of. You're belt driven, do you know the history or when the belt was last changed? If not, do it now before it costs you your engine.

Have to double check with my mechanic on that one.

 

[2016 4Runner SR5]

Have to double check with my mechanic on that one.

Your mechanic won't know unless he happened to be the one to change it last. If no one knows, just do it before you're rebuilding the top half of your engine like I am. I'm doing all the work other than the machine work on the heads and it'll still cost me about $1200-$1500 If I was having a shop do this work, It would be about $5000 or more. Roughly 30 hours of labor for what i'm doing at roughly $100 an hour so $3000 in labor alone.

 

[thegipper]

2005 4Runner I recently bought was having random misfire codes for a while also. End result? Timing chain broke possibly causing valve damage. Do yourself a favor, with your mileage, replace the timing belt set. This one broke at 250K and not a spot of sludge in this engine, it was pretty well taken care of. You're belt driven, do you know the history or when the belt was last changed? If not, do it now before it costs you your engine.

The 3.4L V6 (5VZ-FE) engine is a non interference engine, the belt can break and no damage will be done to the engine. It will just quit running and leave you stranded.

The 4.0L V6 (1GR-FE) is an interference engine but has a timing chain. Much less likely to break but if it does, it is very likely the engine will suffer major damage (bent valves and/or punched holes in the pistons).

Just a heads up.

 

[2016 4Runner SR5]

The 3.4L V6 (5VZ-FE) engine is a non interference engine, the belt can break and no damage will be done to the engine. It will just quit running and leave you stranded.

The 4.0L V6 (1GR-FE) is an interference engine but has a timing chain. Much less likely to break but if it does, it is very likely the engine will suffer major damage (bent valves and/or punched holes in the pistons).

Just a heads up.

I'm aware the 4.0 is an extremely mild interference engine. Sometimes valves are bent, sometimes they aren't. Heads are coming off either way just to be safe and at 250K miles a rebuild is a good idea no matter what.

 

[thegipper]

For sure, not all interference engines are created equal.

the timing belt broke on my 89 VW GLI at idle. When we pulled the engine apart, the valves were bent to shit and one of the pistons actually had a hole in it from the valve hitting it.

The guy that helped me work on it (a VW guru) said he has seen a couple engines like mine have the belt break and no damage was done even though it was the same motor.

Hopefully there is little to no damage on your 4th gen. Good luck

 

[T4R2014]

So much for a chain being superior.

 

[drei4runner29]

I just spoke to the mechanic today and I inquired about the helicoil. He mentioned that he can install the helicoil as long as the stuck spark plug doesn't remove a lot of the metal when forcing the plug out.

He also mentioned that he is concerned for my engine because there's a loud knocking sound coming from my engine. Is this something that I should be worried about? I am oblivious when it comes to anything mechanical. He mentioned that I should change the engine and I can knock two birds with one stone just in case if I have to remove the head if the threads are too worn and a helicoil will not work.

I'm debating if this will be more cost effective or should I just purchase a used 4th gen.

 

[drei4runner29]

So I took my 4runner back to my regular mechanic to get the history of the things I've done to my vehicle in his shop. I asked him to run a test again to see what else is wrong with my car and now it's showing a P0304 and 0306 codes. And I did verify it and that's what it was showing on his scanner.

He said that he can run a compression test and I told him that I will bring it to him on Thursday. He also asked if my vehicle was overheating and I advised him no.

All spark plugs have been changed not too long ago and coils just replaced about a week ago just to be on the safe side.

What else do you think could be wrong with it?

 

[drei4runner29]

Just a quick update on what's going on w/ my 4runner.

So I took it to my original mechanic and he was able to remove the spark plugs that were stuck on cylinders 4 and 6. Both plugs were damaged and was the reason why my vehicle was misfiring. He replaced all plugs and it's been running good so far. And I did replace the plugs maybe a year or so ago so I don't know why the those two plugs were damaged.

The mechanic also did a compression test while the plugs were removed and it was averaging around 175-180 except for cylinder 6 which was around 115-120. He did add oil to cylinder 6 and it bumped it up to around 160-170.

He mentioned that my engine could be going bad due to the low compression and for me to drive it around to see how it goes. I'm currently not working at the moment due to injury and surgery so I'm not driving as much as I can. I did drive my vehicle from Santa Clarita to Huntington Beach and Cerritos this weekend and so far everything seemed fine to me. Does anyone know if what my mechanic said is true or not that my engine could be going bad due to the low compression on cylinder 6?

 

[thegipper]

If the numbers that your mechanic reported are accurate, than the low PSI cylinder could be a problem. 175 on 5 cylinders vs 115 on #6 is an issue since the difference is so great.

I would just keep driving it and see how it goes. If you start getting misfires again on #6 you'll have to consider rebuilding or replacing that engine (or sell the truck).

If you perform a leak down test on that bad cylinder, you'll know where the problem is (rings vs valves).

 

[drei4runner29]

Thanks for the info.


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