Previa 2001 Misfire problem

[EddieBee]

My 2001 VVTI Previa (petrol) with 160,000 miles on the clock is misfiring. The garage has changed the coils and spark plugs but the problem remains. They suggested a worn camshaft or blocked injectors. It would take time to explore these options with no guarantee of success. Does anyone have any suggestions?

[Paulscarbs]

Yes, plug it into a reader.

[EddieBee]

Automania did this and obtained the codes. They said there were misfires on all cylinders. The garage obtained the codes as well. Computers only get you so far!

[Paulscarbs]

I'm sure a Toyota compatible reader could specify exactly where the problem lies. Some readers only go so far.

[RUToyota]

Why did you not get the actual codes they found.??......MAF sensor perhaps.?...bad fuel.?

As Paul says, a half decent OBD code reader should give you good indications of where the problem lies.

[EddieBee]

The garage has the codes but from by browser history the codes were: PO161, PO300, PO301, PO302. PO303, PO304, PO125 and possibly PO1115. I had the descriptions for the codes but they evidently did not help my garage. I'll speak to another garage to see if it is cost effective to explore the problem.

[EddieBee]

I now have the codes from the garage: PO301-304 - misfires on cylinders 1-4. PO300 Random/multiple misfire detected. PO125 insufficient coolant temperature for closed loop fuel control. PO161 02 sensor heater circuit Bank 2 sensor 2. P1155 manufacturer control (googling gave this: Air/fuel ratio sensor heater circuit malfunction Bank 2, sensor 1). The engine light ?EML has been on for years with no problem. Now it's flashing on and off. I'm trying a third garage as the second thought it was too serious for them!

[RUToyota]

Seems to point to possible MAF and Oxy sensor failure (there are 4 oxy sensors on your Previa I believe.)

Having an EML on can't be "no problem"...it's on for a reason and shouldn't be ignored.

[EddieBee]

Thanks for your reply RUToyota. Here's the thread (old) showing people with problems about the EML warning light:

Our light has been on for seven or so years. I'll see if someone can check the MAP and oxy sensors.

[RUToyota]

Having been in "the trade" and buying quite a few Toyotas' over the years, I am well aware of the Oxy sensor issues...they have been quite common on a some models...Previa, petrol Rav 4 etc...not helped by the fact that there are 4 of the beggars...and they are not that cheap to replace (if you buy the correct quality that is)

Thankfully my V6 only has two.!

It has to be worth considering getting the MAF cleaned and/or sorting out your O2/Oxy sensor failures...otherwise your EML will be permanently on and the engine will never run as it should.

[EddieBee]

None of the codes listed indicate problems with the MAF. I don't want the expense of cleaning the MAF and finding the misfiring contues. Googling gave these codes for MAF problems:

[RUToyota]

OK...hope you get it sorted anyway...good luck.

[EddieBee]

I talked to a Toyota specialist over the phone. He thought given the mileage and the codes that it might be worn valve seats. The compression test was fine so I don't know if this agrees with worn valve seats.  It isn't worth investigating so it is now on eBay. I've now bought a 2006 Previa with 57k on the clock. Drives like a dream.

[RUToyota]

OK...given the issues and the mileage perhaps that was the best all round solution.

Enjoy the new Previa.