Engine fires, idles rough shuts off. No codes. Unable to find vehicle service manual online. Unsure if Chilton's covers the removal/replacement procedures for sensors as I will be shotgunning this repair starting with the least expensive parts, TPS throttle position sensor, then O2 sensors, then ECT sensor then VAFM then ECU then wires.

As I have no information as to the testing of each of the sensors. All information I have gained is from online forums and there are many different pinouts and testing ranges given that are contradictory.

It will cost us $300.00 to tow it. And I would like to spend that on fixing it instead. It has run flawlessly until this and has had the best maintenance record possible over an inch thick of receipts.

  • Do you want indications of how to sort the starting problem? Or just the location of the ect sensor?
    – Solar Mike
    Feb 17, 2018 at 22:59

1 Answer 1


Can you confirm if it has good spark during cranking after it quits? Will it run if given ether? Any leaks in the air intake tube between the MAF meter and the throttle body?

The ECT can cause this, it will lie and tell the PCM the engine is -40 deg F, making the engine run really rich. If the MAF fails the engine runs really bad or not at all. It has the most affect on mixture. But is ignored for the first few seconds after start, so it can cause the type of start/stall behavior. I would look there first. That is if spark and fuel are available.

The TPS is unlikely to be the cause. The O2's are highly unlikely since they do not even start working for about 30 seconds and are not given much range of control over mixture, so dont waste money there.

  • On a lot of vehicles, you can semi-quasi test the MAF by pulling the plug on it. This will throw a code, but will also allow the engine to run in an open loop mode or even what's called "speed density". Not sure if the Toyota here has a MAP sensor, but I guess it would need that to run speed density. Pulling the plug on the MAF isn't an all inclusive way to test it, but it is a cheap diagnostic which can help. If you pull the plug and nothing changes (or gets worse), you can probably look elsewhere. Feb 17, 2018 at 19:44
  • @Pᴀᴜʟsᴛᴇʀ2 These engines did not include a MAP so the unplug trick is unavailable in this case. A failed MAF or larger leak in the intake tube is often is a "no run or rough run" event in these early designs. Feb 17, 2018 at 20:04

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