3VZFE open loop mode?

[steveegee]

Hello all, I'm hoping this is the correct forum for technical help. My sister has a 93 Camry with the 3.0L engine. I think it's constantly running in open loop mode. The exhaust is extremely rich. It spits out a LOT of water from the tail pipe and it has a very strong fuel odor. It also emits a lot of white smoke-not black. It's not a headgasket leak. I already did a compression test. There is no coolant loss. There is no oil contamination. Do any of you know how I can verify that the ecm is in open loop mode? Does anyone know what can cause the ecm to remain in open loop mode even after the engine is warmed up?

This car is driving me NUTS! Also, what is the proper method of adjusting the retarded hydraulic cooling fan? I monkeyed with the screw on the P/S pump-big mistake. Thanks in advance.

[chronoti]

no idea on the pump.

but if the engine is in open loop the cel will be on.

http://www.off-road.com/toyota/tech/codes/

pull the codes check back, also make sure the cel turns on when the key is in the on not running postion.

[hill8570]

Pop off the connector on the Engine Coolant Sensor (ECT). If that bad boy is reading low, you're going to have a seriously rich mixture. Popping it off makes the engine fail-safe to "normally warmed up" (82 C).

[LUVLEXUS101]

I have the same issue it sounds like, I get horrible fuel economy. Where is the ect? and let me know how you fix this issue. How would you know if its in open loop mode for sure?

[steveegee]

The CEL is not on. There are no codes stored. It just flashes the "everything is fine-no need to worry" code every 1/2 second.

[steveegee]

I've already tried disconnecting both ECT sensors. One is near the thermostat; one is near the starter. When the one near the thermostat is disconnected or shorted, the cooling fan speeds up (probably self-preservation mode), but no CEL. When I disconnect or short the one near the starter, the CEL turns on, but the fan speed remains the same. Either way, the exhaust still emits a strong fuel odor w/ white smoke & water. That was my attempt at trying to trick the ecm into thinking that the engine was warmed up. BTW, the engine runs great. Plenty of power, no overheating; it even passed emissions after I changed the catalytic converter. I'm sure by now that the new catalytic converter is destroyed from the fuel mixture problem. Weird thing is, after the new cat was installed, the nox increased-almost failed emissions. That reading is what made me wonder what had destroyed the original cat and led me to discover the rich fuel mixture problem.

[hill8570]

Originally Posted by steveegee

I've already tried disconnecting both ECT sensors. One is near the thermostat; one is near the starter. When the one near the thermostat is disconnected or shorted, the cooling fan speeds up (probably self-preservation mode), but no CEL. When I disconnect or short the one near the starter, the CEL turns on, but the fan speed remains the same. Either way, the exhaust still emits a strong fuel odor w/ white smoke & water. That was my attempt at trying to trick the ecm into thinking that the engine was warmed up. BTW, the engine runs great. Plenty of power, no overheating; it even passed emissions after I changed the catalytic converter. I'm sure by now that the new catalytic converter is destroyed from the fuel mixture problem. Weird thing is, after the new cat was installed, the nox increased-almost failed emissions. That reading is what made me wonder what had destroyed the original cat and led me to discover the rich fuel mixture problem.

OK -- ECT and wiring ruled out. What other troubleshooting steps have you done? No point in going over the same land twice.

Lessee...93 3VZ-FE. IIRC, that's got a flap-type MAF instead of heated-wire, so no point in cleaning the wire. Have you tested the MAF, or at least manually diddled the flap it to see if the engine responds?

Seems unlikely that the O2 sensors could be messing with the mix enough to cause a super-rich mixture, but you could disconnect them for a bit to see if anything changes.

Have you tested spark to make sure they're all big and blue? Do all spark plugs look pretty much the same (I'd expect them to look a bit black and fluffy from the rich mixture...if only one looks fluffy, then we start looking for problems specific to that cylinder).

[steveegee]

Yeah, it has the flap MAF. I haven't messed with it yet or tested it. I don't have access to the car right now. I've already tested the O2 sensors. They are both crossing the .5v threshold about 8 times per 10 second interval. That is w/ the engine at approx 1200 rpms. At normal idle, they switch much slower. The lousy testing procedures in the Chiltons did not specify whether the switching was to be counted at 1200 rpms or at normal idle. Anyway, I did disconnect them and there was no change and no CEL. Both O2 sensors are original TOY sensors; I don't know how likely it is that they both would fail. Apparently the ecm/diag was very lenient for 1992 & 1993, so it's plausible that they are both bad. If the Chiltons was a little bit clearer, I would know if they both test good or if they are both bad. The plugs are nice and sooty-all of them. The ignition coil passed the ohm test. It has a newer cap & rotor. The plug wires all passed the ohm test as well. I'm thinking that I'm going to have to go to the ecm and read the inputs from whatever sensors determine open loop mode. I just need to know what voltages it expects and when and from what. I need schematics, diagrams, etc. In short, I need a real manual. I get frustrated w/ Haynes & Chiltons. ARGGGHHH!

[hill8570]

Originally Posted by steveegee

Yeah, it has the flap MAF. I haven't messed with it yet or tested it. I don't have access to the car right now. I've already tested the O2 sensors. They are both crossing the .5v threshold about 8 times per 10 second interval. That is w/ the engine at approx 1200 rpms. At normal idle, they switch much slower. The lousy testing procedures in the Chiltons did not specify whether the switching was to be counted at 1200 rpms or at normal idle. Anyway, I did disconnect them and there was no change and no CEL. Both O2 sensors are original TOY sensors; I don't know how likely it is that they both would fail. Apparently the ecm/diag was very lenient for 1992 & 1993, so it's plausible that they are both bad. If the Chiltons was a little bit clearer, I would know if they both test good or if they are both bad. The plugs are nice and sooty-all of them. The ignition coil passed the ohm test. It has a newer cap & rotor. The plug wires all passed the ohm test as well. I'm thinking that I'm going to have to go to the ecm and read the inputs from whatever sensors determine open loop mode. I just need to know what voltages it expects and when and from what. I need schematics, diagrams, etc. In short, I need a real manual. I get frustrated w/ Haynes & Chiltons. ARGGGHHH!

8 transitions per 10 seconds at 1200rpm is reasonable. Typically you check at 2500rpm for >8 transitions / 10 seconds -- if you're getting 8 transitions at 1200rpm, you'll see more at 2500rpm. You'll never much flip-flop @ idle. That's pretty strange, 'tho -- it indicates that the ECU is controlling OK around stoich, which contradicts the rich fuel smell and sooty plugs. If she's running rich all the time, the O2 sensors should be pegged over to the "rich" side (around 0.9V) instead of telling the ECU that things are hunky-dory and to just tweek around a tiny smidge. You say these are the original O2 sensors -- how many miles do they have on them?

Resistance tests are all well and good for tracing a problem, but I like to ground a plug and watch it's spark before I start playing with a multimeter. I mean, all the measurements in the world don't mean much if you don't have a big, blue spark.

As far as a "real" manual, the 3VZ-FE is a gnarly case...it was only used for a couple of years in the Camry (92 and 93, I think), and those years aren't out on www.camrystuff.com. The 2VZ in the Gen2 is sort-kinda close (closer than the 1MZ in the later Gen3 rigs), but not exactly. For exact, you could go out to Toyota TIS , buy a 2-day pass ($15), and download the pieces of the FSM that you need.

[hill8570]

Oh, another possibility...does the 3VZ have a seperate cold-start injector? If so, might want to check to see if the cold start timing switch isn't turning off -- that could give an awfully rich mixture.

[LUVLEXUS101]

Does the fan run all the time in open loop mode? And OP are you getting horrible gas mileage? I smell lots of fuel out my exhaust, i didnt pass emissions and I get around 12 mpg.

[chronoti]

Originally Posted by LUVLEXUS101

Does the fan run all the time in open loop mode? And OP are you getting horrible gas mileage? I smell lots of fuel out my exhaust, i didnt pass emissions and I get around 12 mpg.

fans are to what sets open loop, if you pull the knock sensor lines it will go in too limp mode and kill timing,and i believe fuel as well.

i would say look at new o2 sensors, rockauto has them right now at ~16 each, even tho you are getting correct oscillation doesn't mean that the sensor is still correctly calibrated.

also make sure the maf flap moves freely and not crudded open

[Eye8Pussies]

Originally Posted by hill8570

Oh, another possibility...does the 3VZ have a seperate cold-start injector? If so, might want to check to see if the cold start timing switch isn't turning off -- that could give an awfully rich mixture.

yes it does, so that could be a possibility