Hello there. I recently availed myself of a 1994 Diamante ES with 160k miles on it for the sum of $1100.
That being said it seems to have a few issues.
It does have a slight tick which may or may not be anything to worry about. I can't locate the source by ear but it may be valve train or the very beginnings of a rod knock. It did not present itself when I was viewing or test driving the car before buying it (go figure). It is usually very quiet but sometimes makes itself known when starting cold and then gets much quieter after having run for a minute. I'll post a video at the end of this post and you may or may not be able to hear it.
The main issue I am having right now is that it seems to be running very rich. You can smell it at idle. It's an eye stinging and watering smell and the exhaust tips are covered in soot and there is a noticeable puffing sound and slightly visible exhaust from the muffler (not so much as you could see a discernable color), and it makes more of a growling sound than a stock exhaust maybe should. It does not smell like burning oil or coolant. That being said I don't actually know what a lean running engine sounds like so it might be that also.
It seems to accelerate fine at part throttle, but there is an intermittent hesitation or miss you might say. Full throttle was actually working fine until today when it started to stumble, fall on it's face, and stop accelerating. No check engine light or any other sign of distress though. Before today I didn't feel as much of a hesitation at full throttle and it didn't seem to be lacking in power all the way through the rev range.
I tried replacing the pcv valve, cleaning the maf with electrical cleaner (I think thats what that is attached to the air filter box, doesn't seem to have a map sensor), and cleaning the throttle body and IAC. All that seems to have accomplished is fixing a low idle issue. Still very rich at idle and doesn't go anywhere at full throttle as of today.
If I blip the throttle (video link below) it makes a sucking sound and seems to hang a bit instead of dropping the revs back down like I was thinking it should. I didn't catch it for the video but sometimes I can get it to stumble if I blip the throttle quickly. Also sometimes after a few blips you can smell fuel when standing over the engine.
The strange thing is that there is not check engine light. I know the light works because I started it without the maf sensor connected by accident.
Could it be bad O2 sensors or a fuel pump? Seems to me it wouldn't run rich with low fuel pressure but it would make sense for it to fall on it's face at full throttle.
I'm not very familiar with this car or engine yet so any help is appreciated.