I've got 240k mile Tacoma with the 3.4. I recently had an issue with warm starts that was cured by cleaning the MAF and IAC valve. I've got a CEL for insufficient coolant temperature. It still runs great, I'm turning upwards of 21mpg, and 90% of the time it's dead smooth.

However, there's a very slight roughness from about 2200-3000 rpms. After 3000 it's just as smooth as can be. I just bought this truck and have zero prior experiance with them, or any other Toyota for that matter. It's possible that it's just normal trait for this motor. If it's not, do any of you have any ideas? I'm going to replace all of my vacuum lines soon (probably this weekend) just because of the miles, not because I think I have a leak. It's got fresh plugs. I'll be picking up a new O2 sensor for the CEL soon, but I don't think that's it. The only other idea I have is the injectors. I have no idea if they've been cleaned before, so I'll have them sent out and bench flowed and cleaned sometime soon. I'm just looking for an interim type thing that I can look into now, in case it's not one of those other things.

 

How does the radiator look? Did you replace the wires w/ the plugs? I suggest taking care of the coolant temperature problem before you spend the $$ for the injector service. The injectors could be causing your roughness between 2200-3000 RPMs, but it could be so many other things too. I would start with the cooling system since that's what the CEL is telling you.

 

why are you replacing the o2 sensor for a CEL for Coolant Temp?



anyways fix the issue with the CEL for the coolant temp sensor then see how it runs, the engine will go from open loop to closed loop when the engine reaches operating temp

in open loop everything is sort of on a preset settings that the manufacture knows the engine will run on, once in closed loop it relies more on what the sensors are telling the ecu about air temp, coolant temp, engine load, engine rpm .... etc to determine timing advance and injector duty cycle.....etc

if you o2 sensor is infact bad it could be due to the fact that the coolant temp sensor is causing the engine to run rich

 

Yes the plug wires are fairly new as well. One of the next things on my list of stuff to do is flush the radiator, however....

...the CEL for "insufficient coolant temperature" is sort of missleading as far as I can tell. All of the service manuals I've found point to an O2 sensor. I guess that could make sense if the O2 sensor is never getting a good reading and forcing it to run in closed loop. The dash temperature guage shows everything working just fine. It's a VERY slight roughness anyway, barely noticeable.

By the way, I was off on my RPM numbers. It exists more from about 1800-2500 rpm, it's smooth after that.

 

the gauge on your dash gets its signal from a coolant temp sending unit, the CEL you have is for a coolant temp sensor, they are two separate things

 

Yeah, I'm not "car dumb" but the wording for these is still pretty confusing. Either way, Here's the codes I have:

P0125 Insufficient coolant temp
P1130 AF sensor perf maff bank one sensor one
P1135 AF sensor heater bank one sensor one

I haven't reset it since I cleaned my MAF and IAC valve so I don't know if that's had any effect on them, although I don't see how it could.

Any thoughts on the fixes? I'm pretty sure an O2 sensor will fix the second two, but from what I've read in some service manuals, a bad O2 could also be causing the first one. My question is which O2 sensor it is? Is "bank one sensor one" the pre-cat or post cat sensor? I assume pre-cat, but I don't know for sure. They're not interchangeable so I'd hate to buy the wrong one.

 

Check your ignition coils too. They have a spring on them for the master plug (the slave uses the wire to go to the other side). I had one where the spring wasn't contacting the plug good enough and causing some hesitation.

 

Ok, dumb question here. Flame away if you'd like.

How the hell do you unplug the O2 sensor? It's on top of the transmission in a place where you can't see it. I don't want to break anything, good Lord that SOB is hard to get to. Any tips?

:edit: nevermind, it's easy if you take off the shift console shift console

iwilli, I checked those a week or two ago, they're all fine.