Questions and Answers

Stanza Choking Out At Speed Q. I'm working on a 1990 Nissan Stanza with 90,000 miles. It idles rough like it's missing every once and a while and has a slight gas smell coming from the exhaust. But it's biggest problem occurs when you're driving. At 3,500 rpm it just fall on its face. As long as you keep it under 3,500 you're fine, but with a little 4-banger that is impossible when you come to a hill of any size.

If the car starts losing speed up a hill, you're tempted to tromp on the gas to kick it down a gear, but that causes the engine to go over the 3,500 rpm mark, then it really loses speed, if you keep the gas pedal down, it will slow down to less than 5 mph, but if you let up on the gas pedal it will speed back up. If your sitting still with it in park or neutral and push slowly on the pedal it will go clear up to 6,500 rpm or higher no problem, but if you tromp on it, the engine speeds up to, once again, 3,500 and bounces between 3,000 and 3,500.

Sorry if I sound redundant, talking about the same thing, but it's all I've got, so I want to explain every last detail. I've changed all the simple things, like plugs and wires, distributor cap and rotor button, and O2 sensor, and none of them seemed to help. I've also checked the self diagnostic computer codes which read out code 55 which means everything is working normal. What am I missing. It seems like the answer should be simple, or am I left with my last resort? TAKING IT TO A PROFESSIONAL.

A. It sounds like it's in Fail Safe Mode. In Fail Safe Mode the ECU will substitute an input signal in the event of a failure in the air flow meter, engine temperature sensor or throttle sensor circuits. The engine will operate at reduced capacity to allow the vehicle to be driven until repairs can be made. The problem with this is when it goes into Fail Safe Mode the Check Engine will come on.

So now we go to the other possibility, a clogged fuel filter or a bad fuel pump.