Engine running lean

[Donald]

I have a '92 Paseo engine(5EFE) in '89 Tercel. My spark plugs are quite white, and not the slightly goldy brown you see when the mixture is correct. I cannot believe I have neglected checking these for so long. Anyway I am pretty sure that I do not have any vacuum leaks, I am running with the stock intake tube with a cone type filter on the end, Pacesetter header and a 2" exhaust pipe all the way except the original catalitic converter is still in.
My fuel pressure is good.

How should I go about enrichening my mixture?
Will repositioning the throttle position sensor make a difference?
Do I need larger injectors? I remember seeing somewhere that injectors from a Supra (what year I don't remember) will fit right into the 5EFE head and plug into the connectors, and they have a larger spray nozzle. can anybody confirm this, and do you think it will help?

[NickR]

I'm really not sure about this, Donald, but I thought that all modern engines tended to run "lean", in the sense that the spark plugs normally come out looking a bit white. I thought that O2 sensors, computers, and fuel injection allowed the engines to be programmed to run closer to the edge of "too lean", giving gains in fuel economy and emissions.

I could be wrong, and somebody please correct me if I am, but you might want to check that white spark plugs really do indicate a problem before trying to fix it.

[enerjohn]

I wonder if the grade of fuel would have anything to do with it. Or mabye fuel additives.
My tips were very white also.

[Donald]

I have never altered the intake or exhaust systems of a FI engine before, so I am a little green with this, but from a omparison to the plugs on all my other FI cars that have not been modified, I would say that these are excessively white. The center ceramic section looks like a plug that has never been in a running engine. The inner bore of the metal part with the threads has a slight sooty coating which looks normal. The electrodes have a light gray coating that could be from fuel additives. I am going to try and get some photos soon amd post them.

I have been feeling a sensation of lean condition since I put the headers and exhaust on, and I have spent a lot of time checking and replacing vacuum hoses to eliminate leaks.
I thought that the computer would compensate for those changes, but apparently not enough.

At some speeds on the express way, when I let off the gas, the car will accelerate just a little before decellerating. It is only a momentary thing that I have not been able to get a passenger to feel. This is a sure sine of lean mixture I believe.

[Ryoga]

Two words: MAP sensor.

ANYTHING you do to change the air flow to/from your engine will change what MAP reading indicates what engine load, etc. This is the reason the Civic crowd LOVES fuel pressure risers. Maybe you should get one

[NickR]

Originally Posted by Ryoga

Two words: MAP sensor.

Interesting possibility. Is the Tercel MAP sensor a wire filament, through which a current is flowing, and the flow of air over the wire cools it down, and affects the measured electrical resistance? If os, then if that wire gets dirty it will stay hotter, and the ecu will interpret this higher temperature as meaning that less air if flowing past the MAP sensor than is really flowing past, so it will reduce the amount of fuel? If so, a dirty MAP sensor would cause it to run lean. (But wouldn't the O2 sensor compensate?)

If the MAP is a wire filament, it can be cleaned (carefully) by spraying it with brake cleaner, I believe).

[Tercel GTS]

You're thinking of an air flow meter, a map sensor just has a small vacuum hose.

[kamesama980]

did you ever reset the ECU after the changes? if not, it will be adapting to the new conditions from previous, rather than just learning the new conditions.

[Donald]

No. I didn't reset the ECU. How do you do that? I thought it would reset if power was removed. (disconnect the battery)

[NickR]

Originally Posted by Tercel GTS

You're thinking of an air flow meter, a map sensor just has a small vacuum hose.

Oops! Yes, I was thinking of a MAF.

I think you can reset the ecu by disconnecting battery, then pressing the brake pedal, or turning on the headlights. for about 30 seconds, to drain any residual charge. But if the battery was disconnected for some time, it would probably have reset the ecu.

[Donald]

Yeah. The battery has been disconnected a few times since the changes. I'll try the lights thing tomorrow and see if it helps.

Advancing the throttle position sensor seems to help a little with the lean sensation at accelleration, but it might all be in my mind. I haven't been on the express way without traffic to really see.

I haven't heard from anybody about the Supra injectors ............... ?
Does anybody know if they will work?