Rocker arm blew hole in engine after replacing catalytic converter why?

(2010-05-30 10:53:01)

1. Charlote Says: Have a 2005 Toyota Tacoma 4 cylinder, 4x4 2.7 l engine ,current miles 175,000. Had to replace catalytic converter at 80,000 1 st time.
Check engine light came on Wednesday 174,500 miles codes: P0138,P0420,P0456. Mechanics replaced catalytic converter and O2 censor. Sunday, 500 miles later check engine light came on codes P0138, P0456, P2433 engine caught fire due to rocker arm coming loose and blowing a hole in the engine block. I want to know if the mechanics could have misdiagnosed the check engine light originally. Symptom:bad cat problem Real problem: over rich fuel system needing valve adjustment?
When I had the cat replaced the second time I asked the mechanic the cause for cat going bad, he said misfiring. Rocker arms only come loose if they are depressurized, maybe from misfire, and some say the main cause of a fallen rocker arm is from excessive carbon build up.
I am at a total loss, and dont know enough about engines to understand why a rocker head would come looses and punch a hole in the engine, when I just had the car in the shop. Are the oxygen sensors, secondary air injection system , and evaporative emission sensors connected to the rocker arms?
I just paid $2,000 for the new cat and looking at $3,000 for new used engine. Could the dealership prevented this failure because they did not diagnose and fix the problem that caused the misfire that lead to the converter failure?

Anything would help. Thank you Charlotte

2. wildmanny2 Says: The dealership did not cause the engine to break in any way,either through misdiagnosis or poor workmanship.It just plain broke down.What do you expect from an engine with almost 175,000 miles?Maybe you should deal with reality and not look for a scapegoat.

3. Robert M Says: You are right to assume fault lies somewhere. Typically on a Toyota in perfect running condition, the converter(s) should last for the lifetime of the vehicle. Your description of engine problem is unclear to me, though. A rocker arm will not blow a hole through the engine block. It might cause a valve to get caught up in the piston, however. Your REAL problem has a few possible causes. Later model foreign engines are VERY complex and usually have variable valve timing with camshafts that adjust their positions based upon sensor and engine loads. If you have been using an oil that is NOT approved by Toyota, your camshafts may have not moved into their proper positions at the proper time and cuased this issue. You shoud ONLY use a synthetic oil that "meets or exceeds the requirements for Toyota" I would be using Mobil One, ELF, Eneos, or Pennzoil Ultra. Even Amsoil!! These oils will prevent future denegration of your complex valve train. WHen a converter acts up like yours did, it usually indicates that the fuel mixture is off, or that the fuel QUALITY is just not good enough for your car. It can also indicate that your IDLE AIR CONTROL VALVE is clogged up (with bad oil) and not copperating with your engine control computer. This valve should be checked and ALWAYS be show room clean to operate as it should. It makes fine tuning of your fuel/air mixture possible. Your engine is most likely a multiple valve engine. THis means that your hydraulic valve lifters AND your timing chain or belt is hydraulically controlled. Imagine one of these items getting clogged up with conventional oil with sludge!! IT throws everything OFF!! READ about "TOP TIER" fuels on the web. IT is very educational. Modern fuels need to have the appropriate mix of detergent and fire power to do their job best. CHEAP fuel will cause damage to the engine if used over and over again. I wish I could see your engine personally. I usually can tell what tod oand what to recommend for your particular car based upon experience. GOOD LUCK!!

4. ken k Says: goodness charlotte/needs an engine and now you know how long a toyota engine lasts

5. STEVEN F Says: My 15 year old care has SLIGHTLY more miles than your 5 year old car. You are driving your car into the ground. Forget spending $3,000 for a new engine. Spend $3,000 on a replacement car. You are looking for something CHEAP, but mechanically sound. As much as you drive, NOTHING will be worth $3,000 by the end of this year.