Lean Condition Trigger CE? Excessive Blowby (1 Viewer)

[landtoy80]

If there is a issue with motor that makes you motor run lean (like a bad vacuum leak or something) and the ECU can't correct the air fuel mixture, will the CE light come on before damage to motor occurs?

Wanting to know if my excessive blowby is or can make the motor run leaner than the ECU can adjust?

If so, would I be better of rerouting the excessive blowby back to the air cleaner so that the VAF meter can help adjust flow.
OR will that cause even more issues with blowby gasses flowing past the VAF meter?

Not going to fix motor, just milking out the last of the 80's life till I can afford another vehicle.

 

[landtank]

I did a test and actually had the fuel trims over 40% and the engine still kept the AFR at 14.7. The CEL would come on at 20%, well before it ever got to 40%.

 

[landtoy80]

Landtank, Can you enplane what you are saying (I don't have much knowledge in this are)?
What do you mean my "fuel trims over 40%"? How did you do the test?
Is this with a OBD2 with scanner or on OBD1 with a scope?

You say the CEL comes on at 20%. Does that mean if its out of spec by 20% over the 14.7?

Is there a way to hook up an multimeter on a OBD1 to read the O2's AFM?

 

[landtank]

the system works by using the readings from the O2 sensors to adjust the fuel trims (control variables) to maintain an AFR (air fuel ratio)of 14.7.

So if the O2 sensors show a lean running engine the ECU adjusts the Fuel trims by adding fuel until the 14.7 is reached and maintained.

Toyota programmed the ECU to trigger a CEL when those fuel trims reach 20%

In my testing I was able to create a situation where the ECU was had adjusted the fuel trims to 40% and the engine was still running an AFR of 14.7.

So with no CEL for bad O2s it's unlikely you are running lean unless the O2s are bad and giving the ECU bad readings.

 

[landtoy80]

Right now I am venting the cranks through the pcv and to atmosphere at same time. That is, I left the pcv valve hooked up to the intake plenum and removed the intake port on the valve cover that goes to the throttle body port. I plugged the port on the throttle body.

At idle I get a positive flow of blowby gasses, liquids and tan colored crud from the hose that vents to atmosphere. Not sure how much more or less the flow of blowby gasses are while driving.

When stopped, the fumes can get overwhelming if there is no wind. So I want to vent the gasses back to the motor. I also don't want to drive past one of the road side portable emissions stations with it bellering out toxic gasses.

I considered buying the Envalve to replace the pcv valve. You plug the intake port on the valve cover that goes to the throttle body and replace the pcv with the Envalve but was worried about running lean with the added blowby gasses. The valve puts a negative pressure in the crankcase thus removing more gasses than the pcv can.

I tested by drilling out a OEM pcv valve and plugged the intake valve cover port. Hooked up a vacuum gauge and there was negative pressure in the crankcase. I quickly remove the system as I worried about lean conditions.

I also worried about a backfire and damage to motor with no one way valve in the pcv.

How often is there a backfire in the 1fzfe?
Could it be happening and we just don't here it or do all backfires result in a Big Bang?

I guess I could save $55 and find a one way valve and install it on the pcv hose to intake plenum. Guess I could experiment with different size tube connectors to restrict flow so the I keep a negative pressure in the crankcase but not overwhelm the intake with too much gasses.

I used a catch can and that reduced the stink but it feeezes up in cold weather as there is a lot of water in the blowby gas.

 

[inkpot]

You realize that your blowby gases are rich with combustible oil vapors/mist? Not likely to create a lean condition when added to the intake stream as originally designed.

 

[landtoy80]

Well, after testing with an adjustable homemade pcv valve to see how much vacuum is in crankcase, I found out why I has so much gasses exiting out the vent port. The piece of hose and a splice in it were restricting the flow of crankcase gasses through the pcv valve. The hose is narrower, plus the bend in hose along with the splice I put in it when I was working on a catch can for the pcv hose were the problem.

With a larger hose, I hardly have any positive pressure in the crankcase till I put a load on the motor. The vent hose side should be able to remove the pressure.

During the test a couple thing happened that I didn't like.
1 To get enough vacuum in the crankcase to suck out gasses I had to get over 15 on the vacuum gauge. Anything over 10 would cause the motor to suck in. When that happened I could here a shuttering scraping noise from the harmonic balancer area. I assume it was sucking the play in the crank??? That can't be good.

2 I could hold enough vacuum so that the motor didn't make the noise at low speeds but once over 50 mph or pulling a hill, I would lose vacuum and have pressure in crankcase.

I need to now rig up a way fitting to see if I have pressure or vacuum when driving with the vent hooked back up to the port.

It's good to know that my motor is not in as bad of shape as I thought. Lesson learned. Use OEM hoses! Or hoses that will not restrict the flow of gasses.


I have to say, I am amazed that you 80 is still running with all the stupid mistakes I have done to it over the years.
Just turned 458,000 today

 

[landtoy80]

Also. With the pcv vacuum hose disconnected from the pcv valve and motor running, it triggered the CEL.