1995 Tercel: Getting the RPMs Down

[MacWord]

I've read through a couple of older threads on the Tercel, and I'm still trying to figure the viability of getting my Terc to run at lower RPM.

This is a car that I used to own, and am now buying it back. It's a straight '95 Tercel with 4 spd manual, and manual steering. A good setup for some modding.

Two issues that plagued me when I had the car before.

1. The final drive RPMs were too high

2. The car ran rich.

The best mpg I could muster was around 41...and I'm looking for 50.

It doesn't look like a lot is gained with the 5 spd manual swap for all the work that it takes.

What about running slight larger tires?

Any help from the Tercel owners would be helpful...thanks

[Saberj2x]

mill a custom 4th gear...

slightly larger tires won't do much, your car would then need more power to turn them and in city conditions you'd probably end up using more gas. I used to have bigger tires, now I got light rims and slightly smaller tires, handles city drive with ease.

[Daox]

Welcome to EM MacWord.

The only option for a transmission swap is a 5th generation (1995+) 5 speed. At 55 mph, that should drop your rpms from 2530 to 2200. Its not a huge decrease unfortunately. Larger tires won't do much for you either and as Saberj2x said they'll also increase weight.

If your car is running rich, there is something wrong and its likely an O2 sensor. How do you know it is running rich?

Also, what speed are you traveling at?

[MacWord]

Two reasons I suspect that it is running rich...

1. Mileage in both city and highway situations seems too low. (calculated mathematically and with scan gauge)

2. Black sooty deposits inside tail pipe seem excessive over other vehicles in the driveway. Also see black/sooty coating on plugs. Compression is excellent.

At lower speeds, the car bucks and jolts.

[Daox]

Is there a check engine light on in the car? If so, what is the code?

If not, I'd pull your spark plugs to see if they're black to verify rich operating conditions. If they are black, I'd probably look at replacing the upstream O2 sensor.

[Backtobasics]

I concur. The pre converter oxygen sensor provide the computer instant feedback on air fuel ratio and amount of unburned fuel in exhaust.
I would talk to Toyota, perhaps they can give the computer a reflash. They may have had issues with calibration that they may have a new flash for?

[MacWord]

I'm getting the Tercel back this weekend and will check for codes. A few months ago when I owned it the first time, the codes it was throwing were P0170 and I believe P0401. The latter was EGR, I think. Codes were thrown intermittently...sometimes not for weeks.

[Daox]

Yeah, the EGR will clog up after 100-130k miles on that engine. I recommend disassembling it and cleaning out the valve, the pipe to the intake manifold, and as much as you can get into the head too.

In any case, you should get the car working properly before you begin to modify it. You'll see better gains from fixing stuff than modding stuff.

[MacWord]

Agreed...I know this car is capable of getting close to 50 mpg, but I've never seen it. I think the main issue is getting the rich mixture under control.

I did clean the EGR tube and such with no changes in the code or performace.

[bluejoey]

I've got a '95 auto. I've cleaned the EGR repeatedly but haven't been able to get in there deep enough to keep the code from returning. There's a good video on Youtube on cleaning the EGR; check it out.

That said, I'd pull the plugs and replace them as needed. That cleared up a misfire on mine. I'd also invest in an Ultraguage if you haven't already; it's good for reading codes, but the real value comes from helping you mod your driving style.

The best highway mpg I've gotten on mine is 45 in the winter, and I know I can easily push that to 50 and beyond once the weather warms up. Similarly, I've had city trips that cracked 40; driving mods will get you the numbers you're looking for once you've cleared any glaring mechanical errors.