NuclearBacon

Hello USMB!!! I have a 2003 Baja 5 speed N/A with the 2.5L engine. I just put in a new (rebuilt) engine and new (rebuilt) transmission (150 miles now on the running gear). The reason for the new running gear is a story in itself. It now runs great with a nice amount of power and a good idle. The problem is the dreaded P0420. I have replaced the rear O2 sensor with a new Denso (the correct one), however the P0420 still returns. It easily sets all the monitors (53 MPH for 3-5 minutes with 1/4 to 3/4 fuel and no speed variation or brake tapping), but at the same time throws a "pending P0420" thus I know the "check engine light" is not far behind (and, of course, it was). The readings are as follows. The front A/F sensor consistently reads 2.0 to 2.1 volts with an occasional dip to 1.9 volts. A very smooth sine wave. The fuel system remains "closed" during these runs. The rear O2 sensor (unfortunately) reads from .1 through .9 volts. The graph of the rear O2 sensor looks like the teeth of a saw between .1 and .9 volts instead of a nice gradual sine wave between .4 and .7 or .8 volts. The new and old O2 sensors read about the same. Backing off down a small hill under compression with my foot off the throttle produces a front A/F sensor voltage of 5.1 volts, a rear O2 voltage of .000 to .005 volts, and an "open" the fuel system. Any throttle pressure on that hill almost instantly returns the readings to the ones already listed. The exhaust temperature going into the catalytic converter reads around 390 to 420 degrees. The exhaust temperature leaving the catalytic converter reads about 490 to 510 degrees. That leads me to believe the catalytic converter is probably working OK. My only hope (short of buying a new catalytic converter - $$$$) is the front A/F sensor is faulty and reading incorrectly. Is a consistent voltage reading for the front A/F sensor of 2.0 to 2.1 volts the correct range for a 2003 Baja 2.5 non-turbo. I've read that the range should be 2.4 to 4.0 volts, meaning I may be running too rich (see LTFT and STFT below), possibly due to a bad A/F sensor. I failed to mention I have already checked for vacuum leaks, exhaust leaks, etc. All is well. I also have fresh premium Chevron fuel in the tank. Again, the engine runs and idles as if nothing is wrong. Instantly starts, nice amount of power (still new so I haven't pushed it super hard), hits 70+ on the freeway with light throttle pressure, good acceleration from a stop, etc. Nothing should be wrong or is wrong with the engine. I'm leaning toward a bad front A/F sensor giving me a reading outside the computer's parameters, thus ultimately causing my P0420. I haven't dealt with the fuel filter, injectors, fuel pressure regulator, etc because there are no driveability problems, thus I feel it is reasonably safe to ASSUME (I know) the fuel system is OK. My LTFT and STFT all are in the -2 to +2 range, mostly hovering around zero. I would think a fuel system problem ultimately causing my P0420 would show up in the fuel trim readings. What is the correct voltage range for a front A/F sensor on a 2003 Baja 2.5L N/A? If mine is out of range, do you think a new A/F sensor ($130) might be my solution? If not, what do you think might make my P0420 go away so I can get my smog check and my current tags? I don't want to use a spark plug anti-fouler on the rear O2 sensor because the smog stations check for that here in California, thus I would fail my smog check the minute they saw it (as you know, it is easily seen from the engine compartment). Could someone with a Baja, or Legacy with the same engine and no check engine light illuminated, go for a quick ride with their scanner hooked up to read the front A/F sensor, then report back to me their voltage figures? That real world test would, at least, give me a starting point to solve this problem instead of just throwing parts at the car (read rear O2 sensor). Thank you!

Idle air control valve... the hose was disconnected. car runs perfectly I did need that MAF, cars running great!!!

Hello! after selling my EA82T racecar to my buddy, he's been driving it around all over, and today when he got in it, it fired right up as usual, but when the turbo light comes on, it sounds like a pretty bad knock only on boost. Kinda like a HLA but louder, and again, only on boost. Cold engine, warm engine, but if its sitting idling parked, and you rev it, you cannot get the same sound out of it. I'm not to familiar with turbo sounds (for diagnosis) but i would think its...the turbo? no smoke, just a knock. I have a mechanics stethascope, but i cannot get the sound under the hood when its parked! Ideas oh wise ones???? Thank you!

TPS + MAF = Car ran crappy, dies TPS (no MAF) = Car idles, dies under power, but runs otherwise. MAF (no TPS) = Car idles high, dies. IAC Plugged in No leaks from MAF to throttle body All Vaccum hoses good. I didnt try to move over my turbo legacy MAF, since I saw it was 5 wire (92 legacy), then I went to the junkyard, grabbed a MAF that looked identical off of a 94 legacy (again 5 wire, but looked identical) wanted to take it home to try, and when I got to the counter, the pick a part yard wanted $75 bucks. SEVENTY FIVE BUCKS. WTF. I left it there. Question 1: Can I use my turbo legacy MAF to test? Question 2: Anyone got a MAF they're willing to sell for $20 + shipping?

The IAC is connected. I have a MAF from the Ej22T legacy. Defninilty going to give this a shot interesting! (writes down as well) I will check. Correct. The reason I went for the MAF in the first place with no codes, is I remember fixing an EA82 that wouldnt run, the PCV valve had gone wonky and oil pressure built inside the crankcase pushing oil up into the intake plenum AND dripping all the way down into the MAF! Unplugging the MAF, and starting on a whim, allowed the car to enter limp home mode (or whenever there is a check engine light, = limp home mode) and ...allowed me to limp home. I'll go try each of these and report back! Thank you!

But! When I go unplug the MAF, the car idles just fine... but has no power under load. I tried cleaning the connector to the MAF, as well as the connectors on the MAF. Didn't spray any MAF cleaner (saw it at the store) , but was curious about it dying under load... feels like it cuts out. I just did a complete head gasket on this car, with the engine removed. The car had overheated as it was a new vehicle bought by a friend of mine. I have no idea the previous history of the car besides it showing up to my house overheated. Could I have possibly skipped a tooth on the timing belt? it seems to idle ok with no MAF connected... so i figured I timed it correctly... Ideas? Oh! and the MAF doesnt throw a code when its plugged in (and i rev it to keep it running, trying to get it to throw a MAF code with it plugged in) I have cleared the computer and the only code it throws is the MAF when its unplugged.

Thanks everyone for your replies!!! I'll go down and get a new filter asap I'm *thinking* about purchasing another blown 2.5rs and rebuilding it... not to this level... but rebuilding it to keep yet another on the road. Just over 1300 miles down and running great!

Sweet! Got my prodrive sticker in, checked my tolerances, and put the belt cover on the engine. Took some final pics What a fish sees. . . As of this moment, the car has 1200 miles on it Labour of love or whatever the @#% the saying is. Car runs PERFECT ! Mostly wanted to share with everyone on this site. When I first got here, I could barely change sparkplugs... ...now look at me Thank you everyone! I owe this build to you! *bows*

This morning I woke up nervous and excited. I pushed the car out into the driveway, pulled the carpet up, and found the magic plate. I've seen it on my turbo legacy, I just figured ... actually I just didnt think about it. Unplugged and set to go (the coil too)... I turned the engine over... ..waiting for the oil light to turn off... Doing a max set of 12 seconds per key turn, I waited for the oil light to turn off..... on the 5th set of key tuns, I still had a solid light. I figured that the assembly lube that I used and coated the metal surfaces with, would give me about 5 seconds of run time without oil being circulated if for some reason the pump wasn't functioning. Heres the oil pan and my fancy cool magnetic drain plug + group n mounts! I plug in the fuel pump, secure it, connect the coil, check the fluids for the 100,000,000th time, and sit inside the driver seat. ...and I sit. Keeping in mind I put a new fuel filter in, had the entire intake apart, and depressurized the fuel system a month before... I turn the key... after about 6 seconds,... The engine comes to life! And the oil pressure light instantly goes off!!! ...sidenote. My thoughts on the oil pressure light... I think that the starter couldnt turn the engine over fast enough to give the proper pressure to turn the light off, yet enough speed or function to allow the pump to suck up oil and transport it where it needed to be on initial startup... I allow the car to warm up, idle for a bit, and I turn it off to check the vitals. Nothing out the bottom. nothing out the top (except smoke, but a normal amount it seemed, no odd smells etc) --Insert Video of Initial Startup Here Soon!-- Everything looks great!! I then go for my break in run. I drive 1.3 miles to the location, then get to third gear for my 30-50 runs. I do 20 sets, and the engine feels GREAT! So I give her a good wash, and take her around for about 60 miles. Oil = perfect Coolant = perfect Throttle feel = perfect. Everything = perfect. I'll check tomorrow as I drive. But I believe I'm in pretty good shape. Heres some pics for a parting shot I think I might sleep in the drivers seat. . . Sub + Helmet. You never know when you'll need one!