99 Tacoma Help!!!!!

Ok guys. Have 99 Tacoma PreRunner, 6 cylinder. Several months ago it was giving a code that indicated that an O2 sensor was bad. Can't remember which one it was. My son actually drives the truck, was in town for the Thanksgiving holidays. I decided to change both sensors since they were really easy to get to. The CEL was actually not on anymore but the truck was really running bad at anything over half throttle. I mean it would LAY DOWN on you if you got on it hard. So... changed both sensors, no change. Have since changed the mass air flow sensor, fuel filter, new catalytic converter, new plugs and wires, new coil packs, and new air filter. All to no avail. Mechanic was going to try and check fuel pressure but couldn't find a place to do it. O2 sensors were Bosch. Read where they are not liked very well by Toyotas but it was running bad prior to the change. Was thinking that it might be the fuel pump. Any similar problems??? Please help!!!!

 

clean the MAF sensor first then test it with a meter, if that's not it test the fuel pressure a lot of times a week fuel pressure will cause a vehicle to run bad and not throw a code

 

Brand new MAF sensor.

 

all that and you haven't replaced the cheapest and easiest part yet, under the drivers seat on the frame rail is the fuel filter, replace it.

even if that's not it, it is something you do for routine maint.

 

Yeah he got it changed...

 

ok, I missed that

 

+1. Sounds like a lot of money went out the door 'guessing'.

You need codes pulled. There can be code(s) pending that are readable, but have not had enough keycycles to set the CEL yet.

And why did the previous CEL extinguish? These things don't just heal themselves..........

 

Yeah, but even with the guessing, a lot of those things were needed. Guess I'll end up at a Yota dealership and let them diagnose it.

 

Like BPS99 states, get codes pulled. Any auto chain will do it for free if you don't have a scan tool.

All that work done, but have you cleaned the throttle body? If the valve is gummed up it can be starving the system of O2. Maybe it is not opening properly. Pull the air system and watch it as someone presses down on the gas pedal. Clean it - just be sure to use throttle body cleaner.

I have seen posts where people get some gel like stuff and proceed to spray an entire can at it. Bahh. Toothbrush, clean rag, $9 bottle of cleaner and use it sparingly. Will shine it up nice and leave you enough fluid to do it about 37x more.

 

Ok, it was the crankshaft position sensor.

 

^^ Right on. Congrats!

 

Glad you got it. The FSM for Toyota's (certainly for my Camry) list that as one of the sensors that is involved in getting the mixture right, so idle issue, accell issues, that is one to test (ECT, MAF, TPS, Injectors, Coil, etc.)