1994 Saab 900S Losing power

saab
900

#1

Yesterday, while driving home from work, my car started what I can best describe as losing power. The car is a 1994 Saab 900S with a stick shift. First, I was going up a fairly steep hill and I felt a momentary hesitation. Then, a few minutes later, I came to a stop at a stop sign near the top of a hill. I started to pull out and then the car again lost power after a moment. The engine sound dropped like it wasn’t getting sufficient fuel, then if I let up on the gas pedal it would catch, then drop again. If I keep my foot on the gas, the rpms will slowly drop rather than revving as if it slipped out of gear. If I was very very careful with acceleration, it seems mostly ok though it occasionally falters just driving along. The issue is worst when trying to accelerate. Recently, I did let the fuel get down to the point where the low fuel light came on and I’m overdue for an oil change but I have made sure that the oil is not low and the gas tank is full. I’m wondering if it could be a dirty fuel filter or something relatively simple like that.



If there is further information required, I will try to answer to the best of my ability.



Jo


#2

It could very well be that the fuel pump is failing. If the fuel filter has not been changed on a regular basis (15k miles or more often if fuel contamination is suspected) this could point even more to a pump problem.

For what it’s worth, I change the filters in my cars every 15k miles and recently decided to inspect the filter on one of them even though it been changed only 6k miles previously.
It was partially clogged and while a car may still run fine with a filter in this condition it can shorten pump life a bit due to the pump having to work harder.


#3

Thank you. I believe the fuel pump was replaced about this time last year so I’m really hoping it’s not the fuel pump again. Is there a chance that the fuel filter is too clogged so that even though the pump is working, insufficient fuel is going through?


#4

It’s doubtful that the pump is failing again. The filter is something to consider and that is something that must be changed when the pump is swapped out.

If the problem is not the filter then figuring this out becomes a bit tougher. You would need to start by having the car checked for any codes that may exist and go from there.
(Wild guessing a bit, a vacuum leak or MAF sensor problem could cause something like this.)


#5

I checked my records and it was just the fuel pump relay that was replaced, not the fuel pump itself. I recall it was doing something this last fall but a vial of fuel cleaner fixed it. I suppose I should invest in another vial of that as a starting point.

Jo


#6

Problem is still recurring, usually most evident in May/June. Vehicle will lose power - not electrical but the tachometer falls even if you have your foot on the gas. This happens primarily when the car is warm, usually having been driven for at least 45 minutes. It is most evident in city driving; I’ve felt fluctuations in the power on the highway but it picks back up. In slower driving it can get to the point where I’m stopped on the side of the road because the vehicle loses power as soon as you put it under any real load. Since I live in a hilly area, that means I can’t get very far. The local mechanics are stumped and because they never have time to drive the car for a prolonged period, it won’t do it for them. It seems like if it was the fuel pump, it would have gone out completely by now.


#7

Get the fuel pressure tested.


#8

My guess would be on the fuel pump and odds are the pump relay was not really needed. They seldom fail and usually the relay is replaced as part of the WAGing diagnosis. (Wild Axx Guessing)

In a rare case where the relay may be faulty to some extent, that failure is often due to a worn and dragging fuel pump.
Pumps can fail in different ways. Some just go bellyup and the engine will never restart again or it may be hit and miss; the pump may go months or weeks between spells where it causes the engine to die.