Corolla SE Saloon Automatic occasional misfiring

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Corolla SE Saloon Automatic occasional misfiring

My corolla SE Saloon Auto 2004with 80,000 KM done has developed a strange & difficult to trace fault.
Occasionally (sometimes after 100 Km , sometimes after 800 KM) it starts misfiring with a little black smoke at low rpms (800-1500 rpm). This condition persists for 4-5 minutes & then vanishes itself.
The 'Check engine Warning Light' on dash board does not come up due to which no Error Code is being generated & saved in the ECU.
I took it to Toyota capital motors twice. They connected their diagnostic computer but since at that time the car was fine so they were unable to trace the fault. They replaced air,fuel filter, auto transmission fluid, spark plugs & made a bill of around Rs 13,000/-.Second time thay checked pressure of fuel pump & also flushed fuel tank.
After few days the problem occured again & they said that v r unable to trace the fault since no fault code is aval in the ECU. They say that let the fault aggravate otherwise it is just a hit & try.
They suspect the air intake sensor but are not sure.
I dont think that there is any other workshop in pindi / Isb with more advance eqpt than Toyota Motors.
Is their any solution to this problem or should i send the car to Toyota Indus Karcahi??

Gari.pk User 5166 asked on 26 Jul 2010 13:22:31 pm

1 Answer

670 views |

Zain - on 26 Jul 2010 13:22:56 pm

IS your car on cng too???????????

We call this problem a TB (Throttle Body) or Tuberclosis. When it happens, the Throttle Body becomes a combustion chamber as pre-dominated by a spark or valve problem.

As known to us, there is two areas that you need to be checking for:

Electrical Sparks

The most common is the spark plug. Over here, we recommend that Bosch Super 4 or NGK BP6ES to be used. These spark plug can tolerate high temperature or commonly known as 'Cold Plugs'.

Using the right spark plug is important as mentioned by several experts in this forum. The reason is simple.

A poor spark plug (or likely Hot Plug) may be still very hot (glowing hot) and can cause a Pre-detonation to next incoming Air/CNG mixture. Since the Intake Valve is still open on 'Chamber 2', the Hot Plug detonate the gas unnecessarily in this chamber.

Case 1 - HOT Plug

The fire will travel out from the No 2 Chamber Intake Valve and lighting a fire fuse to all the way up to the Throttle Body, and exploding pre-mixed Air/CNG in the TB. Your vehicle should jerk or choke immediately after that. In worst case, your EFI car will have the Throttle Body Butterfly valve blown out or a burnt airfliter

Spark Plug Cable Cross-Fire

Alternatively, using non-original spark plug cable can cause a cross-fire. As the electric coil/distributor gives power (voltage) to Cable 1, the current jumps over to Cable 2 as well. Both spark plug 1 & 2 open fires, and you will experience a situation similar to Hot Plug. But only this time around, the cross-firing is lighting up cable 2 and fire fuse to the TB again.

Intake Valve

Some vehicle has an adjustment Valve Tappet. These vehicle needs to be regularly adjusted if NOT the intake valve will not close tightly. Again, the firing of that chamber will light a fire-fuse (via Air/CNG) from the Intake Valve gap and into the TB. Hydraulic Valve is likely not to have this problem.

Once we experience a special case, the owner of a EFI vehicle complaint about backfire. He has been using his car for 12 months and not such problem before. It just started recently, after he has a radiator flushout. The problem turned out to be - he also replace a non-original electric coil on his EFI-based distributor. We have changed all components and nothing work. Finally we found the problem to be changing the low-amps/voltage electric coil.

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