6mpg from a 3fe!!! What gives!!!! (1 Viewer)

[Dave 2000]

Bloody hell 6 MPG! I simply could not afford to have a car that returned that kind of mileage, very strange that the motor runs so well, I would have expected rough running/black smoke. Blocked cats should throw a code but not serious enough to light up the MIL.

I don't suppose it is worth mentioning my HDJ 80 get 26/27 MPG?..................No, I did not think so.

regards

Dave

 

[jonheld]

I believe some of the 3fe era motors from toyota had distributor problems and don't advance correctly when they go bad.. I would swap in another distributor and see what happens. Those EFI systems of that era could have a host of problems without throwing a check engine light. Plugged cat is a possibility, pull the o2 out and drive it, if you have more power than the cat is plugged. Anyway I would start with the distributor in my opinion and go from their.

3FE distributors don't advance or retard like counterweighted 2F distributors. There are fixed field coils in the housing. Ignition timing is all handled by the ECU. The jumper wire in the diagnostic port disables the ECU control of timing and allows you to set the static timing by rotating the housing in relation to the flywheel. Once the jumper is removed the ECU controls ignition timing according to its programming.
The ECU doesn't "know" that the static position has been changed. It's just delaying or advancing pulses to the igniter according to the input from sensors.
There are no crank position sensors on a 3FE.

 

[White Stripe]

3FE distributors don't advance or retard like counterweighted 2F distributors. There are fixed field coils in the housing. Ignition timing is all handled by the ECU. The jumper wire in the diagnostic port disables the ECU control of timing and allows you to set the static timing by rotating the housing in relation to the flywheel. Once the jumper is removed the ECU controls ignition timing according to its programming.
The ECU doesn't "know" that the static position has been changed. It's just delaying or advancing pulses to the igniter according to the input from sensors.
There are no crank position sensors on a 3FE.

So the distributor on these is basically the cam position sensor right? Otherwise the motor won't have a reference at all of how to retard or advance spark. At one point I knew more about these distributors, but its been a while. I believe that on one of my 3vz motors the distributor had screwed up, was over advancing at higher rpms, and grenaded the motor.

 

[jonheld]

Essentially yes. But in this case the cam/crank position sensor is adjustable, as you can rotate the distributor. Again, 1986 technology.

 

[LS1FJ40]

Essentially yes. But in this case the cam/crank position sensor is adjustable, as you can rotate the distributor. Again, 1986 technology.

1986 was a good year.

 

[Alleycats]

So what happens if you adjust timing without the jumper?

 

[jonheld]

So what happens if you adjust timing without the jumper?

Very good question. I have never tried to do this. I would assume that the timing would appear to be off as the ECU is pushing it in one direction or the other. I seem to remember someone trying this at one point.

This also brings up the question that @White Stripe posted. What is the ECU using as a reference for timing? I have gone over all the inputs to the ECU many times and cannot answer this question. Therefore I have been of the mindset that there is no reference other than the pick up coil in the distributor and that the ECU pushes/pulls timing according to its internal programming. The system "assumes" that mechanical static timing is set within parameters outlined by the FSM.
If this was not the case and there was an actual reference point, the ECU would be able to compensate regardless of distributor rotational position. However, we know this is not the case and that timing can be advanced/retarded.

 

[Chester]

So what happens if you adjust timing without the jumper?

I have tried this on a 3FE in a '62. It seemed to be hovering around 13 deg advanced, varying and fuzzy to watch, as the timing fluctuates with the feedback loop from sensors through the CPU.

 

[Eicca]

So what happens if you adjust timing without the jumper?

I did mine by ear, advancing it as far as I could without getting ping. It made a noticeable difference--felt more alive, not as sluggish. This was right before the road trip where I peaked at 15mpg. And THAT was right before we lifted it and stuck it on 33s.

 

[Alleycats]

So I gauge my timing by how far my distributor is turned and my bolt is right in the middle of the range. I have a timing light but I had pinging so I stopped trusting my timing light, now I just go by ear > ergo if I get pinging it must be too advanced.

 

[Hankg550]

Bloody hell 6 MPG! I simply could not afford to have a car that returned that kind of mileage, very strange that the motor runs so well, I would have expected rough running/black smoke. Blocked cats should throw a code but not serious enough to light up the MIL.

I don't suppose it is worth mentioning my HDJ 80 get 26/27 MPG?..................No, I did not think so.

regards

Dave

Seriously?? I had no idea. I thought the JDM diesels we’re getting maybe 1-2 more mpg then a standard US petrol 4.5 engine?

 

[Dave 2000]

I have seen 30 MPG before, the diesels are brilliant!

regards

Dave

 

[leonard_nemoy]

Seriously?? I had no idea. I thought the JDM diesels we’re getting maybe 1-2 more mpg then a standard US petrol 4.5 engine?

Holy thread resurrection batman

 

[Hankg550]

I have seen 30 MPG before, the diesels are brilliant!

regards

Dave

That’s amazing. I think I get like 10-12 on my 97 and I don’t even pay attention to what I get on my 92

Holy thread resurrection batman

blame the search button. I don’t do a good job paying attention to the dates

 

[Hankg550]

Holy thread resurrection batman

I think I was doing a search on catalytic converter deletes on the 3FE. I think 92 was deleted by PO. I don’t see any cats.

 

[Marco Lau]

i advanced mine till it started knocking slightly under load and i dialed it back just enough till no more knocking. I still get about 12-13 mpg on 37s on highway. and about 9-10 city

 

[Dave 2000]

That’s amazing. I think I get like 10-12 on my 97 and I don’t even pay attention to what I get on my 92

blame the search button. I don’t do a good job paying attention to the dates

The diesels are brilliant IMO, as I grew older and whilst I still like speed the authorities continue to reduce speed limits and increase the amount of camera's on the road in the name of 'safety'.....(cough) bull**** so a more sedate....ish pace of life is being forced upon me.

So a diesel 80 for me was the way to go.


regards

Dave