P0300-P0302 - P0304 - P0306

1994 Camry 1MZFE 168K

Car suddenly started running bad, idles rough, very poor acceleration either cold or warmed up. I live in the sticks, car will eventually (1 - 2 miles) get up to 75mph if throttle is held steady, no power if opened up.

No apparent vacuum leaks, compression 180PSI on all, good primary resistance on all 6 coil packs, new plugs, blue spark. EGR valve closing. Cleaned MAF & car stalls if MAF is unplugged. New fuel filter, 43 PSI fuel pressure (spec). Dropped converter - can see through, unbolted muffler in-pipe - no difference.

Freeze frame

Parked
675 RPM
Load 16.0%
STFT1 +12.5%
LTFT1 +21.0%
STFT2 -4.6%
LTFT2 -7.7%
STFT3 -69.7%
LTFT3 -39.7%
STFT4 -5.1%
LTFT4 -7.5%
O2 Sen Mon Inc

Parked
1733 RPM
Load 14.1%
STFT1 +3.4%
LTFT1 +12.5%
STFT2 0.0%
LTFT2 +16.7%
STFT3 -72.9%
LTFT3 +1.5%
STFT4 +57.0%
LTFT4 -22.9%
O2 Sen Mon Inc

Driving
2473 RPM
Load 51.3%
STFT1 -2.2%
LTFT1 +12.5%
STFT2 +1.5%
LTFT2 -7.5%
STFT3 -51.0%
LTFT3 +1.5%
STFT4 +89.8%
LTFT4 -17.4%
O2 Sen Mon Inc

I understand fuel trim for banks 1 & 2, but what is STFT3, LTFT3, STFT4, and LTFT4? What input does the PCM use for those?

Any help appreciated.

st is short term fuel trim, lt is long term fuel trim, the numbers are for the different 02 sensors, if you don't have 4 02's then 3 and 4 probaly mean nothing. Have you verified the timing belt hasn't skipped? I'd like to see what some individual 02s are switching like on this car!

There is an O2 sensor in each banks' exhaust mainfold and one downstream of the catalytic (total 3). Trim numbers for 3 & 4 are out to lunch, why I'm curious as to what the PCM is using for input and what fuel output is being augmented or decremented from the baseline program. If the timing belt had slipped I would think I'd see a lower compression number on one or both banks. Thanks.

Well yeah trim numbers for 3 and 4 are out! Im unsure with only 3 02's how they get a measurement for 4 with a 3 sensor set up!

Like Comp said, you'll ahve to ignore the fuel trim readings that are beyond 1 and 2 ST and LT. They're for more sensors which you don't have, so ignore the redundancy. Your LTFT are way out, like COMP said indicating a vacuum leak or bad o2 sensors

Under "I/M Monitors" screen, it has "Oxygen Sens Mon-----Inc". Supposedly meaning "vehicle was not driven enough to complete the monitor". But the engine had been running for over an hour in each case. If the car is cold and I disconnect the battery (20 minutes - to clear the computer's memory) and then start it and drive off, it still runs like crap. This is in open loop, with a cleared computer it should run fine via the baseline program, no? Thus I would think I could eliminate the O2 sensors.

Today with a cold motor I start it and pull each coil pack off the plug to check for RPM drop. Cyls 1, 3, 5 result in a noticeable drop, 2, 4, 6, result in a no real difference, but it can't be running on just 1, 3, & 5. After it warms up it responds the same. So I think it is mis-firing equally on 2, 4, & 6. Wait, that's what P0302, P0304, P0306 are. I'm going nowhere.

The way you're going about thinking theres a baseline for 02's missing isn't really the best way to go about it, taking the 02's electrically out of the circuit will keep the monitors from completing obviously and not necessarily default it to the point where it will reun better, it may in fact make it run worse or the same as it is! Without a scope I'd probably throw a new dealer 02 sensor in that side of the engine that's logging the misfires assuming like you said there's no fuel flow issue, wirinng issue vaccum leak to that side of the engine or camshaft moved!

I wasn't clear. What I meant was that after clearing the computer and driving it cold and finding that it ran like crap, that I could eliminate the O2 sensors as the cause of the problem. Not that they could be removed electrically.

But I'll try a new O2 sensor and see what happens.

That clears the adaptives but if the engine is still overfuelling or underfuelling because of an 02 stuck at 1 extreme then it's unlikley it would have any positive effect at all ergo it still needs to be replaced or at least checked more thoruoughly!