2001 shuttering to start, won't move in drive.

1. When the Prius is IG-OFF, you should be able to rotate the throttle shaft easily with your hand. The spring does not exert that much force.
2. When the Prius is READY you should not be able to rotate the throttle shaft as the motor should hold it in the position desired by the engine ECU. So if you actually can rotate it, there is something wrong - maybe the motor is slipping on the throttle shaft.
3. I would say the spark plugs are in marginal condition: a) the rust around the porcelain shows that water had gotten into the spark plug wells at some point which would encourage a misfire. b) the tips show more carbon accumulation than I would deem normal for 15K miles and this implies the air/fuel mixture is rich.

 

Replace the throttle body assembly which includes the throttle motor. A failed assembly is likely the root of your engine's problems.

Your post 36 says that the engine will run but the car will not move. Is the hybrid vehicle warning icon in the MFD still on?

If yes, it is likely that your powertrain has more than engine problems. You would need to be able to retrieve the DTC logged by the hybrid vehicle and traction battery ECUs to get a clue about whether the failure is related to the transaxle, inverter, hybrid vehicle ECU itself, or who knows what.

 

So now that the engine can run, what happens when you put the gear selector into D or R?

 

Don't worry, they'll come back. But it sounds like you need a decent device to retrieve them. Again, I highly recommend Mini VCI which emulates Toyota Techstream.

 

This sent me back out to my car to check, and I was mistaken earlier when I wrote that the ECM would fight you in IG-ON. It only takes an active interest in throttle position when actually (as Patrick points out) READY.

So the OP being able to turn the throttle with equal ease in IG-OFF or IG-ON is actually normal (or the same as my car, anyway, which isn't misbehaving). Now, if I actually start the engine and then try to turn the shaft, I can move it by a tiny hair, and then clearly feel the ECM saying "oh, no you don't!"

I kind of agree with the OP's description of the spring force - it's not monstrous, but rather uncomfortable to hold in the open position for a length of time.

So it seems to me the evidence here doesn't suggest any trouble with the throttle assembly.

I'm still not super anxious about lacking the codes from the HV ECU. We know there's a misfiring engine, and the HV ECU will definitely log a problem if it can't get enough power from the engine, and I'm sure by reading its codes we'd see that - but that's a consequence of the problem we already know we have. I'd be comfortable with getting the engine running on all cylinders, and seeing what the HV ECU has to say then.

I might be more cautious if there were any symptoms suggesting other, expensive, HV-related problems in addition to the engine misfire, and if the question were whether to fix the misfire or scrap the car. But that doesn't seem to be the case here, at least from what I've read.

-Chap

 

Looking at the plugs in that photo, am I seeing things, or is one a bit more carbon-coated than the rest? That might happen if that cylinder is getting an extra-rich mixture. That could happen if that injector is leaking or flowing too much fuel for some reason. It could also happen if the other injectors are flowing too little, and that one isn't as bad ... because the ECM can only see oxygen readings and trim injector timing for the engine as a whole, so if it's getting too little fuel on average it will make all injection pulses longer including for the one that's not as bad, which will then be on the rich side.

-Chap

 

DTC P0172 means the air/fuel ratio is too rich, which some of your spark plugs show with their tips being excessively dark.

From the 2G factory repair manual, here are likely causes. Of these, a bad injector or a dirty MAF sensor are the most likely:

Injector leak, blockage
Mass air flow meter
Engine coolant temperature sensor
Ignition system
Fuel pressure
Gas leakage in exhaust system
Open or short in A/F sensor (bank 1, sensor 1) circuit (Classic has an oxygen sensor in the B1S1 position, not an air/fuel ratio sensor)
A/F sensor (bank 1, sensor 1)
A/F sensor heater
EFI M relay (Classic relay is probably named something else)
ECM

 

Using your ScanGauge you should be able to see the readings that the MAF and engine coolant temperature sensors are giving you, just to see if they seem reasonable. After sufficient time to warm up, when the upper radiator hose warm, the coolant reading should be around 82 to 85 Celsius. Also the fuel-trim reading using the XGAUGE definition from a couple posts up.

You might try taking the MAF sensor out and spraying some MAF cleaner (only MAF cleaner, it's highly specialized stuff) on the sensing elements, one of which is hard to see buried inside a passage. It should only be touched by the spray of cleaner, no brushes, Q-tips, or any other foreign objects.

I have this set of reconditioned original-equipment injectors available, if you're interested.

-Chap

 

I would definitely limit any 20-mile trips in a car misfiring on two cylinders. The OEM catalytic converter is rather expensive to replace. Some people do find muffler shops to cut it and weld something else in, but if you can avoid melting it in the first place, you're money ahead.

-Chap

 

1. Have you inspected the spark igniters: looking for corrosion in the wiring harness connectors, and cracks or burn marks in the plastic? Moisten a paper towel with a solvent like paint thinner and wipe off the dirt on the igniter body. Each igniter should look like a new part after it is cleaned. If there are any physical flaws, replace the igniters.
2. The iridium spark plugs don't look wonderful in your photos and I suggest you consider replacing them.
3. Since you currently have misfire issues with cylinders 1 and 4: swap the igniter from cylinder 2 to cylinder 1 and vice versa. See if the misfire moves from P0301 to P0302. If yes, then you know the igniter is at fault and it should be replaced. Then do a similar drill with the cylinder 4 igniter.
4. After taking care of 1-3 above which are easy issues to deal with, if you still are logging P030x codes then the fuel injectors probably need to be replaced. That will be more difficult because you have to relieve the fuel line pressure (by removing the circuit opening relay while the engine is running) and then remove the fuel rail when the Prius is IG-OFF. Hopefully you can do this without removing the engine valve cover - there should be sufficient play in the fuel rail line which runs through the loop in the valve cover. Make sure you use new rubber O-rings to seal the injectors when reinstalled, you don't want high pressure fuel spraying everywhere in the engine compartment.

 

I have seen plenty of misfire codes that occur because of the spark ignitors/coil packs. They can be relatively inexpensive (under $70) and not too hard too replace (under 30 minutes). Take a look on ebay.

Sometimes a single ignitor is bad, but the problem caries over to the next cylinder in the sequence.

You're very close to getting this in good running condition. Keep persevering!