I noticed on a 600 mile trip (my first in this car, its actually my brothers) that the car was getting rather poor fuel economy, around 13-15 mpg on the highway doing 70-75 mph. At times, it would refuse to go over about 70 mph, the engine was just not making any power at around 3500 rpm, and even less at 4500 after it downshifted. This seemed to cure itself when the car was turned off for a while and then turned on again.

In addition, earlier today it just refused to start. I had been inside a store for about 20 min, came out, and it would crank over but not start whereas previously it would fire up almost instantly. There was spark, and it smelled of fuel. When I pulled the fuse for the fuel pump, thinking it was flooded, it would turn over, catch and run for a second or so, then die. After that when the fuse was back in, it would refuse to even so much as sputter. I finally got it started and running by cranking it with the fuse out til it caught and then quickly putting the fuse back in, however it was still pretty sluggish. Upon getting home, i turned it off, then tried to start it again, just to see if it would; it didnt.

On the drive home the idle also seemed a little high and it bounced around a bit... this sounds like a vacuum line to me, but I'm unfamiliar with these cars.

What are the most likely causes of these symptoms? Is there a sensor that typically goes bad that would cause the ECU to make it run very rich? Is there a place online where I could find a factory service manual to help with tracking vacuum lines and diagnosing the car's many problems? Thanks very much!

Pete

 

Ok, after looking through a bunch of similar-ish threads (poor fuel economy, running rich etc), it seems like the things I need to check are the:

Fuel Pressure Regulator - do these typically go bad? Whats the stock fuel pressure at idle and/or WOT?
Air Filter - I guess since it could restrict air flow, altho the MAF should just be reading the air that gets past it, in general itd just be a good thing to do anyway
Fuel Filter - A good thing to do, since i have no idea when it was last done
MAF - It seems like these go bad pretty often, is this an issue that would affect the NA V6?
O2 sensor - Is this a generic 2 or 3 wire, or one of the bosch 5-wire plugs, or none of the above? I saw a post where it was mentioned a replacement was about $200, that sounds like a pretty ridiculous price considering you can get a whole wideband 02 sensor and programable cable for that.
Cleaning Throttle Body - How would this get dirty? How would cleaning it help any, unless its getting propped open? I'm just confused as to how this would make the car run rich.
Bad Spark Timing - is this something that normally gets too far off? I know its a distributor-based system, but the coil itself seems fine since the spark was nice and strong, and im guessing here, but it seems to be computer controlled.

Am I missing anything? I know the wiring on this car is horrendous anyway, and i'll be checking into that, but are there any other common things? Thanks!

Pete