69 1/2 Six PAck Bee

I am curious about how you other 3VZE owners' trucks act when cold. My 1990 SR5 4x4 runs really good and has just had a major tune-up including injectors, valve adjust (what a PITA!!) and timing belt. It has a brand new ECT sensor, cold start injector and time switch (I verified the injector operation outside of the manifold too) and the TPS is adjusted perfectly. The VAF meter is clean and operates freely. I get no troube codes so I assume all is well.

Even before the tune-up it had had the same condition..here goes...

Outside temp~45 degrees. Starts up okay..cranks about 1.5-2 seconds and fires. I figure this to be normal. I step into the go pedal (while sitting still) and the engine stumbles and I can see a good deal of black smoke from the tailpipe but it clears right out immediatly and continues to fast-idle @1400RPM and will lessen in engine speed as it continues to run as expected. If I rap the pedal again and again it will still hesitate and puff black smoke. If I ease into the throttle, however, it is fine. Now then, I am figuring that this is the way Toyota programmed these things in cold "open loop" mode but then again I have other F.I. vehicles that do not exhibit this sort of cold operation either.
Do these 3.0's run like this cold or am I full of it and shold be looking at something else?

Thanx,
Bud

Flamedx4

Sounds just like mine (except mine starts Instantly, no crankover at all!)
You sure it's black smoke and not blue smoke?
No reason to rap the gas pedal when cold starting though.

suprathepeg

Sounds to me like valve stem seals are going bad. I had that happen on my supra with only 90k on it. The reason was that it was always parked in the winter and the seals dried up. If you are idling when warm and then hit the gas is there a small puff of smoke? You'll likely not be able to see it but have someone stand behind you and check.

UKMyers

Mine will hesitate a little bit off the bottom when it's cold, like when I take off from a stop sign or something and try to get into it a bit fast.

69 1/2 Six PAck Bee

There is no burning oil as blue smoke would indicate. This is a rich condition. Black exhaust.
After it warms up (>72 degrees c and in closed loop) then all is well. Once warm it will fire off immediately as expected. It is not really sluggish, per se, when I first start off rolling but then again I don't floor it either. It does have trouble starting when cold sometimes. Once in a while I will have to hit the key twice before it will kick over...kinda unusual for an FI engine I thought. So that is when I checked the cold start injector and time switch. It has a longer initial "shot" the colder it is but that's as it should be. Once the engine is warmed up there is no shot at all which means the CS circuit is functioning properly. This is more in relation to an extra-rich, afterstart cold run enrichment as are programmed into all FI systems. I have done several Megasquirt builds and installs so I am well versed on this topic to say the least I am just curious as if this is how Toyota designed their VAFM-equipped engines to operate.These seem to be based on the Bosch K-Jetronic system, IIRC. There is not a lack of (or increase in) fuel pressure upon startup as I have checked that too when I swapped out all of the injectors at tune-up and valve adjust time.
The engine had 150PSI in all 6 holes and the timing is 13 BTDC (with the jumper in place) and I have all new NGK's for the spark duties. The cap and rotor are also new so this thing, for all intents and purposes, is in tip-top shape. I did remove that P.O.S. K & N FIPK (was on it when I bought the truck) and put the stock airbox back in place. Gee, it's amazing how the bottom end grunt came back and the "tuner" sound went bye-bye
Anyway, I am going to check the VAFM just for the hell of it.
Maybe this is how the truck is supposed to be but it still seems strange to me

suprathepeg

Well you are 3 degrees advanced byond factory spec, that might account for your start delay. The truck should run rich when cold though thats what the cold start injector is for. If this was the middle of summer would it still run like this?

On a side note this engine seems to have some have come from the factory with some pretty "safe" tuning all over the place. For example when you open up the intake you see a reduction in performance, this goes against logic though cause your allowing more air to get into combusion chamber and the performance should be accross the board. Others have reported that porting in plenum brings increased performance in the midrange all the way to the top, also seems to defy logic cause you'd think it should only help in the top end. I tend to think that there is a lot of potential in these engines its just not all where you would usually look on a toyota.

69 1/2 Six PAck Bee

Sounds about right. FYI--the CS injector only injects at initial starting...that's all. It does not keep squirting as some people think. This engine runs rich and hesitities (like too big of a pump shot would cause with a carbureted engine) and will continue to do so until warm. yes, it does not make any difference summer or winter. A cold start is a cold start. Just the temperature is more apparant in the winter. The sensors are calibrated for diffierent resistances which are linear in gradiations and proportional to the ambient temperature. That being said, until the engine reaches "closed loop" temperature (around 172 degrees F) then that is when my engine will respond as it shoud. I was just curios as to why Toy would program such a drastic change into the fuel map with such a subtle variance in ambient temperature to closed loop temps.
If I could hack this ECU I would but I am not up on the coding that Toy uses.
I am certain that a good deal of my poorer-than-usual (being that these 3VZE aren't the most fuel efficient engines either ) economy is due to the overrich mixture during cold operation. Fortunately, it warms up fairly rapidly.

I guess I am going to have to live with it.

suprathepeg

Yea I get the impression that the factory fuel map is rich all accross the board. It is very rich after 80% throtle, no wonder a 63mm TB has such an effect at WOT.

From what I can gather two things are killing this motor in its stock form: heat possibly from an inefficient burn and a restrictive intake and exhaust which likely also add to the heat.

I'm still one of the ones who believes that there is potential in these engines. I just think that it is not where we would traditionally find it. If you remove the HG (much, much better ones are now available) and remove the crossover from the mix this is a pretty decent mill. Your not gonna smoke supras with it but there is some potential.

phorensic

To respond to the original post, I think your motor is running perfectly normal. When my 3vze is cold it idles at about 1200RPM and if you rap the throttle real quick it stumbles and then revs. But black smoke coming out when you rap it might not be a good thing depending on how severe it is. If I could see the end of my exhaust it would probably puff a bit of black smoke out when cold and rapping it.

AUYota

Mine will idle high, as high as 2.5K when its cold, and gradually get down to normal idle .5K in about 2 minutes.... I like to wait until its down to .5 because i have a man. trans. and its tougher to control with a 2.5k kick

IS THIS NORMAL!?

suprathepeg

idle at 500 is not normal. When its cold it should idle high and then come down as it warms up.

phorensic

I've never seen a motor cold idle at 2500! And 2 minutes is a very short time to warm up. But the warm idle at 500 is perfectly normal. My 3vze has idled there for most its life, running good, or running bad, or running without a spark plug, lol.

suprathepeg

Mine will. You have to understand that you live in Cali and I live in mid Canada so winter cold start is different I'm sure. The FSM says that it is supposed idle at 800 +/- 100, maybe your idle is set low or your timing is not advanced enough.