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Discussion Starter #1
Good day,

Got a 2007 FJ with 148,000 miles and when I changed cam shaft sensor (cheap China one, $10 bucks!) , I saw the original one is covered thickly in sludge. Someone told that's the sign of a stretched timing chain.

Sometimes kids travel with me, so is it safe to drive with a stretched timing chain?

Also is it better to clean up old cam sensor and place back than China one , as the old one might be covered in sludge that it didn't worked properly or get a new OEM one?

Cleaned mass air flow sensors, cleaned throttle body (that was full of carbon and wasn't even opening or closing, cleaned it). Changed cam sensor too as told before.Disconnected battery , drove for 10 kms, first check engine light came then rest all lights came up - Check engine, slip , VSC track, VSC.

So question is :
1. Anything I should try before thinking about timing chain change?
2. Safe to drive with stretched timing chain?
3. Any other thoughts
1120937
 

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Sludge is an indication of poor maintenance of the engine lubrication system (excessively long oil change interval, poor quality oil, defective crankcase ventilation system, etc.). An elongated timing chain is frequently the result of poor lubricant quality.

It's probably not immediately "dangerous" to drive with an elongated chain, but if it gets elongated enough, it will lose tension, start to "slap", and may break the plastic cam chain guides or jump a tooth on one of the sprockets, which may cause catastrophic engine damage.

First evidence of an elongated chain will be the CEL and a multitude of other warning lights, and various OBDII fault codes for the VVTi system ("cam timing retarded", etc.).

What prompted you to change out the cam timing sensor?
 

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Discussion Starter #3
Sludge is an indication of poor maintenance of the engine lubrication system (excessively long oil change interval, poor quality oil, defective crankcase ventilation system, etc.). An elongated timing chain is frequently the result of poor lubricant quality.

It's probably not immediately "dangerous" to drive with an elongated chain, but if it gets elongated enough, it will lose tension, start to "slap", and may break the plastic cam chain guides or jump a tooth on one of the sprockets, which may cause catastrophic engine damage.

First evidence of an elongated chain will be the CEL and a multitude of other warning lights, and various OBDII fault codes for the VVTi system ("cam timing retarded", etc.).

What prompted you to change out the cam timing sensor?
Thanks so much for the message. I received P0016 01/02 and P0016 02/02 error messages. I saw in Google P0016 is related to cam shaft sensors, thus changed it.

I don't know whether my chains are stretched too, one gentleman told it might be stretched because of that much sludge on that cam sensor.

There is no sound or loss of power right now , Vehicle runs very smooth. So that means there is no immediate danger ? Will there be any warning if the timing chain about to break or something of that sort ?

Thanks so much for taking time to reply.
 

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A timing chain change is a big job. Anything you can do to extend the life of what your engine has left will be wise. The evidence of sludge is a real concern, and could lead to a short engine life in other areas too.

My recommendation is to begin an aggressive oil change interval to try and clean out what is in there. Also, removing the valve cover can tell a lot about the condition of the sludge.

FJ Test is our resident technical expert, let's see what he has to say.
 

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Discussion Starter #6
Thanks so much, yes planning to do
1. Synthetic oil change every 2500 kms.
2 . Use crankcase cleaner.
3. Drop oil pan and clean.
4. Use seafoam.
Anything else?
 

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To really get some indication of how severely sludged your engine is, you need to pull at least one valve cover and actually look at the quantity of sludge present.

If moderately or severely sludged, the risk of using any type of "crankcase cleaner" is that enough sludge will be broken loose to clog the oil pump pickup screen, which will restrict oil pressure and flowrate, and totally destroy the engine (rod and main bearings, crankshaft, camshafts, every moving part).

If the engine is severely sludged, there are really only a few options that I see:
1. Run the engine until it becomes undriveable, or fails to pass emissions requirements. The useful life MIGHT be extended by frequent oil and filter changes using synthetic oil.
2. Replace the engine with a factory crate engine ($$$$$$)
3. Replace the engine with an engine from a low-mileage salvaged FJC or 4Runner engine of the same vintage.
3. Have your engine completely rebuilt by a competent Toyota engine overhaul specialist.

Only replacing the cam chains, guides, tensioner, and probably the VVTi actuators on a severely sludged engine doesn't make any sense.

Here's a fairly severely sludged 1GR-FE top end:
1121003


Here's a catastrophically sludged top end (engine unknown):
1121006
 

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Discussion Starter #8
Thank you so much @FJtest for your input. I truly hope it's not sludged much , I will pull valve cover to see what the condition and will share pic here. Thanks much
 

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Check the chain tensioner while you're in there. If the chain is stretched it will show on the tensioner. It's the 4 bolt cover on the front left of the engine. The shaft will extend out to take up the slack in the chain. Usually you can see oil stain markings on the shaft indicating that it has moved.

 

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My '07 4Runner (same engine) wasn't sludged that badly, main timing chain was elongated and P0016 was recurring. I put ~12K miles on it before disassembling the front to replace the chains and whatnot. No further elongation was observed based on the #1 tensioner plunger position during initial diagnosis and at disassembly 12k miles later. My goal was to reduce the sludge and get a few oil samples to the lab, informing the decision whether to repair the engine or replace it. Shell Rotella T6 diesel truck oil changing it at 2500-3000 mile intervals.

It's still puking up a bit of sludge at each oil change based on oil filter interior (cut open the canister), and flushing the pan (vehicle on ramps passenger side, pushing clean oil down the dipstick tube (high side of the engine) to wash across the oil pan floor. Not as thorough as dropping the sump, but better than leaving the sludge to accumulate.
 

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Discussion Starter #13
Here are some pics of my tensioner just prior to disassembly, new vs. stretched timing chains, and sludge flush output.
Thank you very much. My engine runs very smooth, just like my new 4R, so trying to get as much as out of it before writing it off.

You had any issues driving while driving with stretched chain? Any sounds or slow responsiveness or power loss?
 

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Thank you very much. My engine runs very smooth, just like my new 4R, so trying to get as much as out of it before writing it off.

You had any issues driving while driving with stretched chain? Any sounds or slow responsiveness or power loss?
It was running somewhat "rough" and down on power at low-RPM high-load conditions such as low speed in OD uphill. Not enough to be a problem, but after the new chains and whatnot were installed it was noticeably smoother.
Long Term Fuel Trims were ~3% skewed bank-to-bank, with bank 1 showing consistently ~3% more negative fuel trim vs. bank 2. Without a scanner you'd not know this.

The original owner sold it because it wouldn't pass state emissions inspection with the chronic P0016 error code and check engine light. Apart from that and the risk of the chain failing, the Vehicle Stability Control and Traction Control systems are disabled while the Check Engine light is on..."Christmas Tree" light show. You won't have benefit of those systems and they're nice to have.

First, I'd pull the small 4-bolt inspection cover and grab pics of the #1 tensioner showing plunger extended length, to get an idea of the chain's condition. In my pics, it had 4 or 5 ratchet teeth left before maxing out. If yours is extended longer, the risk of failure is higher.

I'd run oil high in molybdenum disulfide (moly) additives to minimize wear on what's left of the timing chain's pins & bushings, e.g. Pennzoil High Mileage or Quaker State Ultimate Durability. And I'd flush out the pan every oil change as I described earlier.

Another guy here skipped his chain 1 tooth ahead on the #1 bank intake cam sprocket and I considered doing the same. Search on P0016 and you'll find it, big 8-page or longer thread. This seemed to have fixed his P0016, as it advanced the cam closer to zero. Not a hard job, just remove the passenger side valve cover and the 4-bolt inspection cover...bring the crank and intake cam to TDC...remove the #1 chain tensioner carefully...skip the chain 1 tooth as he described in his thread and reassemble.
 

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Discussion Starter #15
It was running somewhat "rough" and down on power at low-RPM high-load conditions such as low speed in OD uphill. Not enough to be a problem, but after the new chains and whatnot were installed it was noticeably smoother.
Long Term Fuel Trims were ~3% skewed bank-to-bank, with bank 1 showing consistently ~3% more negative fuel trim vs. bank 2. Without a scanner you'd not know this.

The original owner sold it because it wouldn't pass state emissions inspection with the chronic P0016 error code and check engine light. Apart from that and the risk of the chain failing, the Vehicle Stability Control and Traction Control systems are disabled while the Check Engine light is on..."Christmas Tree" light show. You won't have benefit of those systems and they're nice to have.

First, I'd pull the small 4-bolt inspection cover and grab pics of the #1 tensioner showing plunger extended length, to get an idea of the chain's condition. In my pics, it had 4 or 5 ratchet teeth left before maxing out. If yours is extended longer, the risk of failure is higher.

I'd run oil high in molybdenum disulfide (moly) additives to minimize wear on what's left of the timing chain's pins & bushings, e.g. Pennzoil High Mileage or Quaker State Ultimate Durability. And I'd flush out the pan every oil change as I described earlier.

Another guy here skipped his chain 1 tooth ahead on the #1 bank intake cam sprocket and I considered doing the same. Search on P0016 and you'll find it, big 8-page or longer thread. This seemed to have fixed his P0016, as it advanced the cam closer to zero. Not a hard job, just remove the passenger side valve cover and the 4-bolt inspection cover...bring the crank and intake cam to TDC...remove the #1 chain tensioner carefully...skip the chain 1 tooth as he described in his thread and reassemble.
Thank you so so much Waypoint
 
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