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Fuel economy, '88 NA Supra

First, a bit of background. I might do better if I fix the transmission and the speedo cable. The speedo cable is broken at the tranny, and needs a new piece to make things right. Only $80 for a 6" piece of cable. This will get the speed sensor in the speedometer feeding to the ECU again (the sensor is working, but because the speedo isn't it registers 0 MPH to the ECU.)

Add to that two broken solenoids in the tranny. Easy to replace, $80 each...

Now, I appear to be getting about 12 MPG with the car...I dunno, because I can't calculate it, because...the speedo doesn't work...

The recent inspection showed HC, CO at perfect levels for a car this old, almost as good as new. The NOx was almost over. I think it passed by 6 points. Indicative of a plugged Cat? There aren't any other driveability problems, the car rips along pretty well.

Now, I can't remember...to reduce NOx, do you Advance the timing, or Retard it? Last summer I set the timing dead nuts on spec, and then played with it slightly to get the car running smooth and get a little OOMPH out of it, only a degree or so one way or the other.

Now, about the roof. I havent been driving with the roof on much, so I suppose this isn't helping, either. But it just seems I wasn't putting this much gas in it the past 3 years...

Reply to
Hachiroku $B%O%A%m%/(B
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High NOx comes from high combustion chamber temperatures, which can be the result of insufficient EGR flow, over-advanced timing, or lean mixture.

Reply to
Ray O

Check for an inop EGR vavle or plugged EGR pasaages.

Advancing the timing tends to raise NOx. If the timing is only off by a degree or two it should be ok.

Reply to
Mike

Guess I'll start by resetting the timing to stock. However, I checked the timing when I got the car, and it was at factory spec, and the NOx was high then, too.

The EGR is easy enough to check; how do I check lean mixture? Tracking this down may also help with my vapor-locking problem, too...

Reply to
hachiroku

Thanks! I'll check the timing again and have a look at the EGR.

Reply to
hachiroku

I responded to your e-mail about the EGR - check your in-box.

You check the mixture by looking at the HC numbers on your emissions test. I don't remember all of the numbers you posted, but I don't think the mixture is too lean.

I have never seen a vapor lock on a fuel-injected Toyota because the higher pressure from the electric pump keeps the fuel in its liquid state while it is in the fuel line.

It is possible that your injectors are a little fouled, try some Chevron Techron, exercise the engine, and see if it clears up. If you can find a shop that has Motor-Vac, I've heard good things about it, from my buddy the Ford master tech and from MDT Tech.

Good luck!

Reply to
Ray O

Ray's telling *ME* to excercise the engine?! ;)

I'll try excercising it with some Techron!

Reply to
hachiroku

LOL...BTW as far as removing bolts, been there, done that, and ruined one engine! (on the Voyager...it was on it's way out anyway!) Yeah, believe me, learned that lesson the hard way! But sometimes, it just can't be avoided. I used that method removing the thermostat housing on the Subaru I was driving this winter, and one of the bolts *still* snapped! Luckily I was able to drill through the bolt, thread it and install a new bolt! Otherwise it would have been off to the junkyard. I put 6,000 miles on it and it's still holding.

Problem with these old cars, things are so 'set in place' that sometimes they end up snapping no matter what you do. When I get a newer car (like the Scion, either new or within 3-4 years old, like the Tercel) I go over everything I think I might have to replace during the time I'll own the car with lubricant, just in case. Even the exhaust bolts, even though it smells for a while. I also oil the cars inside and out and the undercarriage, and this makes any repairs down the road much easier. The guy I got the Celica from oiled it from 1985-1992, and it was much easier to work on!

I use GM Rust Penetrant an Inhibitor. Costs ~$12 for a can 2/3 the size of PB Blaster, but it WORKS!

Reply to
hachiroku

I've had very good luck with the GM and Ford branded chemicals. I would use anti-seize on bolts though.

Reply to
Ray O

My bad, I forgot who I was writing to!

Reply to
Ray O

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