LiCelsior

iTrader: (32)

hello, ive been having a problem with this for a while but dont know what it is. CEL code #25 - Air-fuel ratio lean malfunction. alldata points to a o2 sensor malfunction. but many of my friends said that o2 sensor wouldnt make such problems that im having. parts i changed so far: plugs, plug wires, coolant temp sensor, injectors, fuel filter, passenger side o2 sensor (both sides are seized and threads on the pass o2 sensor was destroyed when taken out, had to weld a new bung and put the new one in but same problem)

problem: first off on cold starts, rpms would go to 1100 then drop to 800, climb back up and drop. on extreme cold temps, it would go to 100 then drop to 600 then clumb up and etc. when warmed up, idles fine but once you go past 3k rpms the car would start to get buck and shake as if the engine isnt getting enough fuel. one of my friends said it could be a fuel pump problem, another said the fuel press regulator could be bad. also getting 15-16mpg mostly all highway 60-70mph.

help please!

-Joe

LiCelsior

iTrader: (32)

just wanted to add, how do u test if the fuel pump and fuel press regulator is working in its specs? thanks.

mitsuguy

iTrader: (2)

you would need to find a way to get a fuel pressure gauge plumbed in there... I know we have a kit at the shop that has the adapters that you plumb in temporarily, but there are also more permanent options as well... I don't believe there is an easily accessible port on the car...

Honestly though, it does sound like an o2 sensor problem. If not O2 sensor, then air flow sensor. O2 sensor is easy to check... get a voltmeter, tap into the wire, you should get a voltage that swings from .1 to .9 volts and back about once a second or two... if it is stuck at .1 volts or lower, even when you rev the car, then the o2 sensor is dead... Again, it really sounds like a dead o2 sensor to me...

LiCelsior

iTrader: (32)

thanks for reply Mistuguy, so you think i should change the driver o2 and see if that makes the difference?

mitsuguy

iTrader: (2)

I would definitely start there...

First, I would check voltages (on both primary o2 sensors) though, make sure we are on the right track...

LiCelsior

iTrader: (32)

well the passenger o2 is brand new. so ill just change the driver one also.

mitsuguy

iTrader: (2)

new does not always equal good or working...

LiCelsior

iTrader: (32)

so what do u recommend me checking? the new o2 sensors?

mitsuguy

iTrader: (2)

well, check the new, check the old... check everything before just randomly replacing it because it is a likely cause...

LiCelsior

iTrader: (32)

bump, Cody i got a video of cold start up on my car, u can hear it missing and by the looks of the exhaust, looks like driver side part of the engine.

http://s254.photobucket.com/albums/h...t=MOV00853.flv

nthach

There's a easy way to check on Toyota engines for fuel - there's a fuel pressure damper on the fuel rail that looks like the fuel pressure regulator, and it's covered with a plastic cap that slips off. On the top part there is a screw - the screw will protrude up when pressure is present or it will collapse down into the cover when there is insufficient pressure.
This trick also works on some Hondas with Denso-made fuel rails, not IPT/Keihin ones.

LiCelsior

iTrader: (32)

oh yea forgot to add, i replaced the o2 sensors and my lean a/f code went away..but another one i forgot about was a RPM signal NO.2 code. so maybe timing belt was installed wrong? camshaft position sensor is bad?

nthach, do u have a picture showing this little trick?

GEORGE_JET

The codes should be two digits, not one. If you had the code before, re-read the code and see what it is. if you did not have the code before, check to see if you knocked anything loose, and then read the codes.

LiCelsior

iTrader: (32)

it was engine code 13.

GEORGE_JET

You changed the timming belt?, I missed that, 13 is for the crank sensor, and includes the relationship to the cams. Did this problem start with the timming belt change? I would recommend re-checking the timming belt, and inspecting the cam sensors, crank sensor. Many engines will start one tooth off, but it won't be driveable.