Questions and Answers

Toyota Pick-up Lean? Q. Dear Sir: I have a 1988 toyota 4x4 pickup with the EFI system. 120,000 miles on truck. Recently it has almost no power, yet will idle smoothly, and I have determined that the fuel supply to the engine is terribly lean. If I remove the air intake hose the engine will quit from receiving the extra air supply. Squirting gas into the intake manifold the engine will accelerate. I changed the fuel filter, and did not find the old one very bad.

I checked the fuel pressure at the inlet to the filter and read 60-80 lbs pressure with the engine not running and the key held in start position. I remove the plug from the O2 sensor and can detect no difference in the running of the engine. (Curse toyota for putting this plug under the carpet, under the seat) I removed the throttle position sensor plug and detect no change in engine running. I also removed the fuse to the engine and again the engine keeps running, albeit poorly. (this fuse is labeled "engine" under the left passenger kick panel I presume it is for the computer.)

I receive no engine warning light while running. With the key on and engine not running, my engine light does come on. Jumper across pins T and E1 on the diagnostic plug I get a flashing engine light. This light flashes exactly twice a second and will flash forever as long as I hold the key on. This flash rate does not match up with any engine codes I have found.

I have read many times that the computer rarely if ever fails, so what else could be the problem? I of course see no obvious broken or mouse chewed wires anyplace.

You should also know of a possible related problem. For ½ a year now, the truck when started has run very rough while cold. After about 2 minutes warm up time the truck will run normally again. The truck ran so rough that I avoid attempting to drive it until it warms up. This started in the winter, and has progressed through the summer, but now in the summer the truck warms up faster of course.

Stop scratching your head why I did not fix this problem sooner. I am guessing that whatever caused the rough idle and skip while warming up has completely failed now. The odd thing is that the engine runs very smooth now when warmed up. It is just so lean that I can get no power out of the engine, and barely limp down a level road in first gear.

I called a local Toyota dealer for a diagnostic check and they refuse to work on any vehicle older then 1994. Is this legal, to not work on Toyotas?? Thank you very much for any advice you may give.

Sincerely,
Kerry

A. Are you sure about that fuel pressure reading? The maximum fuel pressure should only be 44 psi with the Fuel Pressure Regulator (FPR) vacuum hose off and plugged. 60 to 80 psi is way too high and would cause the engine to run rich, not lean.

I'm really confused here. If the pressure is that high and the engine is running lean as it seems to be, you have multiple problems. In the fuel pump there is a pressure relief valve that limits the pressure the pump puts out. An unregulated fuel pump can produce as much as 120 psi of pressure. That valve is probably bad causing the high pressure reading. If the FPR is bad, it's letting the fuel go right back into the tank.

If the Coolant Temperature Switch (for the computer) is shorted, it could be telling the computer that the engine is way hot and cutting the time the injectors open way down. It's also possible the O2 sensor is bad and telling the computer the engine is running rich and the computer is leaning out the engine.

As for the dealer refusing to work on your truck, that is their prerogative. There is no law that says that they have to work on your truck once it is out of warranty. While it is unusual for any shop to turn away work, it is not unheard of. I have done it myself with certain customers that what I make on them just isn't worth the aggravation they cause me. I had one customer that has been kicked out of every shop in town because he was such a PITA. He now has to go out of town to find someone who will work on his cars.

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