Any Ideas?

[leftoverture]

I have a strange problem with my 94. This only happens when I start out with the vehicle cold. It will start out fine, but the first time I stop, when I pressthe gas to start out again, it will have almost no power. Once it makes it about 100 yards or so, boom back to normal and it will be fine the rest of the day. It is definitely not the tranny slipping and it isn't the engine bogging. It's more like it doesn't register the gas pedal being pressed. I already replaced the throttle position sensor. If I can make it a mile or so without stopping, which is almost impossible where I live, it doesn't do this at all. I have codes 171, 172, 181, 186, & 189. Any ideas? Anyone else ever have.something like this?

 

[huntman58]

171 = O2 sensor fault not switching
172 = O2 sensor fault / lean
181 = O2 unable to switch lean part throttle
186 = fault injector pulse width circuit / high
189 = O2 sensor fault unable to switch / lean part throttle

To me it looks like you may have a bad O2 sensor now is it the right or left bank or both I do not know lets hope someone with more knowledge on it jumps in here. What I do not know or believe is that a bad O2 sensor(s) would do what you say yours is doing when you first start out and then after warmed up good it runs okay. To me I would thing something other then or also with the O2 sensors. Maybe a dirty MAF something like that.
Have you tried cleaning your MAF?
Did you check the O2 sensor connectors to make sure there tight and not pinched, corroded or any thing like that?

 

[Roadrunner777]

Shot in the dark:
I think the fact that it does not happen again for the rest of the day is important. Are you in an area that gets a lot of dew in the morning?

This seems like an issue where a sensor with a heater is somehow getting damp. Otherwise, it would happen if you started it in the afternoon. The MAF and the O2 sensors are both possibilities. If the MAF were contaminated, that fits pretty good. Clean the MAF first. You might find some gunk on there that explains everything. I never saw an MAF that didn't need some cleaning, so it's a plus, no matter what. Let's go from there.

Actually, I am also getting a little feeling about fuel. Fuel pressure readings would be interesting too.

 

[leftoverture]

Thanks for the responses. I should mention, when I say it's fine for the rest of the day, I mean as long as I am using it. If it sits 6-8 hours or so, the problem will happen again. With that said, I thought about fuel pressure/delivery. I will have to get out the gage and try testing it. I wonder if I can rig it up so I can read the fuel pressure while I drive to see what the reading would be when the problem occurs. I'm not sure how a dirty MAF would create this problem...wouldn't that affect it all the time? Not that cleaning it would be a bad idea.

 

[Roadrunner777]

On the MAF... essentially what you have is a little tiny heating element and a little tiny thermometer. The goal of the device is to keep the heating element at a certain temperature, so the thermometer is set up to control the amount of power going to the heating element.

Now, you can imagine blowing air on the heating element, that would require more power to keep the element at the goal temperature. Now, add a circuit to measure the power. More airflow requires more power, which is measured by the circuit and reported to the computer. The computer responds with longer injector pulses, or more fuel.

Just to be overly complete, I'll mention that this mechanism reports the amount (mass) of airflow, regardless of atmospheric pressure. So, by the principle of the thing, it compensates for altitude.

The downside of the MAF is that it needs to stay absolutely clean. Dirt causes the whole principle to slow down. The computer looks at this data and the throttle position sensor and looks for the data to match up. More throttle should equal more airflow. If this gets bad enough, it can throw a check engine light.

Ok, in your case, I was stretching a little bit, guessing it was dirty and somehow also getting condensation. Right now, where I live, everything is soaking wet in the morning until the sun is up for a while, so I was probably influenced. But, the fact that it can happen later in the day eliminates this theory.

All of that said, if you have never cleaned it, you probably should. It takes a funny torx bit and a very specific solvent you will only find at a good parts store. It is a spray can labelled MAF Cleaner. Other threads and internet sites have good instructions.

I still think it's fuel though. Maybe a bad pump.