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Hi Everyone,

Hi mate, thanks for this. My IS200 (2002) has shown code P1346 for some time now. VVT valve changed, camshaft position sensor changed even the coil pack, all 6. But this code keeps showing up. The car actually broke down over a year ago because I neglected to get the tensioner changed. The camshaft was replaced as was belts etc. Since being put together again the idling is playing about. I'm pretty sure it wasn't doing this before it broke down. You could be sitting in the car at the lights say and the idle isn't consistent, much to the point of the speeding up the revs and causing the car to shake left to right. Timing has been checked and double checked and is spot on. It's also misfiring on just one cylinder apparently and popping at the exhaust.

Thank you for reading.

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What happened to the engine - why was the camshaft replaced? Any valve damage?

If there is no valve problem, then there is a timing issue. Maybe not between camshaft and crank but between the two camshafts or VVTi components.

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Thank you for taking the time to respond ColinBarber. 
The engine ceased when it broke down just over a year ago. As a result I had to have the following replaced:

  • Cylinder Head complete with valves (fortunately I got a used one off ebay - and was informed that it ran 'just fine' when it was on the car it came from);
  • Timing Belt and Tensioner (as it was suspected that it was the tensioner that caused the problem in the first place);
  • Head bolts and gasket set;
  • Timing Belt Idler.

All of the above changes got the car running again but clearly it was misfiring, only on one cylinder it seems so it's not bad although bad enough to realise it's not running as it should and problematic enough to ignite the engine management light with the code p1346. I've had at least three different garages look at it, including the dealers, the latter charging 'silly money' and charged me for a new coil for one of the cylinders as they located a problem there. Well, still misfiring. So I replaced all the coils just in case, albeit not Delphi ones. The Camshaft position sensor has been replaced as has the vvt valve, former Delphi latter generic.

I've rectified a few advisories on the last MOT and although it's an oldie it is a fine specimen, apart from a scratch or two I hope to get rid. Wheels refurbished and customed to suit the gunmetal grey...

I'm gutted after all the time and energy spent it's still 'playing about'. I've been advised that one of the cylinders in the cylinder head could be screwed. I wish I had got it 'air tested' now before it went in. This has me wondering because the car running like a dream before it broke down. 

Anyway, I was told the ECU, or wires leading from the vvt valve to the ECU are possibly at fault and resetting the ECU could clear the misfiring. Is that even so? I'm not convinced, but I'm not a mechanic.

This problem I see as having been brought on by myself. A careful driver with enough respect for the car to polish it every couple of days and driving very low mileage annually, between 3K - 4Konly. So when time came for the big service, the one which dictates to change the belts every 80K, or whatever it is or every 7 years, whatever come first. I ignored the every 7 years because I only did around 25K and the belt looked as good as new. Little did I know that the tensioner would 'mess up my programme'. Anyway, I'm where I am now for whatever reason... blah blah

Thank you,

Leon

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Oh, and the timing is spot on. No problem there.

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The Lexus workshop manual only give to areas of investigation for this fault code - incorrect mechanical timing or a faulty ECU.

The fault is generated by comparing the time between crankshaft and camshaft signals by the ECU - faulty wiring would prevent the signals from being received and trigger a different fault code so I cannot really see it being a wiring issue.

If a cylinder misfire is the cause of the 1346 error code then I would expect normal misfire codes to also be generated.

Have the cylinders been compression tested to see if one isn't quite right?

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Hi thanks again. 

What you have said makes perfect sense to me. 

Unfortunately the cylinders were not tested. This sounds like a good option and it sounds like you know your way around the car engine. So, if you can tell me the easiest way to get them compression tested as it looks like my only option. I like easy. 

The spark plugs have been checked and are fine, apparently. 

 

Yours, 

Leon 

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any mobile mechanic would have one, or you can buy from from Halfords, Eurocarparts and probably amazon too. e.g:

https://www.halfords.com/tools/hand-tools/automotive-tools/laser-compression-tester-221918.html

 

you take out all the plugs, fit the testing into one of the plug holes and crank the engine over for 5 seconds with the throttle wide open to take a reading. Then repeat on all the remaining cylinders. The actual reading isn't too important, probably around 180 to 200 psi but it is the difference between the cylinders (ideally within 10% of each other).

If one is low then there is a problem with that cylinder, and you can do some additional tests to try and determine if it is an issue with the piston, head gasket or valves.

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Tank you once again for your response.

Wow, sounds easy enough, at least in the first instance. Yet after any diagnosis located at this point of the engine it sounds like the only remedy is the necessity to strip most of the engine to get to it? Running into the £100s, wouldn't you agree?

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Could it even be a plug problem? Although I was told they are fine it would be a lot easier to change...

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What's annoying is when the car is stationary it begins to shake every so often. Potential throttle body problem? But would this lead to a misfire? 🤔

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