2001 3RZ-FE 2WD RPMs drop with each restart

I've been lurking on these forums since we picked up this Tacoma, and you all have been really knowledgeable and helpful - I'm hoping you can get me over my latest hurdle. A brief background up to this point: 1. EFI fuse was blowing, fuel pump was identified as culprit and replaced (not by me), kept blowing, I found a short in the cable coming off the battery, repaired it, no blown fuses since. 2. Daughter reported bad MPG, low idle, and CEL (unknown code), I cleaned the MAF, TB, IACV, replaced some hoses, seemed to fix low idle at first. 3. About 10 miles later, CEL back on with codes P0171, P0402 (EGR Flow), P1130, and P1135. Stored codes at this point were reported as P0125 insufficient coolant temp.

My most recent attempt after this was to replace the VSV jus tonight. After I replaced it, I started it up and it idled at about 1455, which felt high but ok. I let it run for a few minutes, then turned it off and restarted it (I think this part of the cycling process maybe?) to get about 1027 for the idle. It felt pretty good there, so I shut it off and then by chance a few minutes later I needed to move it - it started and idled at about 700, started shuddering/shaking, and died when I put it in gear. Now it won't start again, and I've had enough for tonight.

Am I on the right track for the EGR excessive flow code? No codes have come back tonight but I haven't driven it anywhere, and I don't understand why the RPMs would keep dropping with each restart. Any advice you all have is appreciated.

 

I would start with the P0125 code for the following reason. If the engine computer (PCM) does not get a reading that the motor is up to operating temp the PCM thinks it is a cold all of the time and the fuel injection and ignition timing and other things controlled will be in “warm up mode”. This could be due to no thermostat or a stuck open thermostat or a sending unit. There are 2 coolant sending units on your motor, one has 2 wires and IIRC, is by the upper radiator hose on the head. The other sending unit is on the back of the cylinder head and this one is for the dash temp gauge. You want the 2 wire unit.

 

Thanks for that! I will take a look at that sending unit you suggested. Should I be testing that electrically or looking at the live data on the code reader for something in particular?

 

Not an expert on EGR, but sounds like your air intake at idle is having problems

CTS/thermostat may be an issue too like said above but it wouldn't explain dying when you put it in gear

 

Finally had a chance to get back into this; it wouldn't start because the EFI fuse had blown again, so I should have have checked the easy stuff first.

Today: I replaced the fuse, started it and let it run for 10 - 20 minutes. After the first 5 minutes, the idle started to drop again. I eventually had to keep the gas pedal down a little to keep it from dying. The short term fuel trim was reading 20% (long was zero since system had been reset), the engine coolant temp raised to about 190F (which I understand to be normal so maybe not the coolant sending unit?) the MAF was at 8.65 g/s, spark advance was 15 degrees, throttle position at 11.4. When I eventually let off the gas, it died and then wouldn't restart.

I checked and the EFI fuse had blown again. If I don't reset the computer by removing the negative lead, it immediately blows the new EFI fuse while trying to start. If I reset the computer and a new fuse, I can get the same results with it running for 10-20 minutes.

Does this provide any additional value that would make you look at one thing or another? I haven't replaced the O2 sensors yet, and since they are often mentioned with EFI fuses blowing I'm thinking that is the next step.

 

Yes that MAF reading double what it should be at idle, yours should be 2.7 to 3 ish. The standard is 1 g/sec per liter displacement.

 

I have more parts coming in, and I am going to replace them one at a time to see which one it might be. Even if I find one part was the source of the problem, I will probably keep them all since this thing has 340K miles on it. I ordered O2 sensors and gaskets, MAF sensor, IAC valve and gasket, and PCV valve. I will come back with an update, probably this next weekend.

 

O2 Sensors and MAF finally replaced, I had to fight those O2 sensor nuts. Now it pops the EFI fuse with just turning the key to on, without even trying to start the thing. I think I might have to tow it to a shop.