1997 SL2 vibration, low mpg, starting & stalling issues
I recently purchased a 1997 Saturn SL2 1.9L MPFI 4 door with 134k miles. It is the first Saturn I have ever owned so I do not have experience with this make of car.
Initially I knew that it sounded a little loud (exhaust and whine) and that it had more vibration (from the engine) when running than I would consider normal far any car. I have checked the mileage and I am getting about 25 mpg with an even mix of city/hiway. From listening to other Saturn SL2 owners I was expecting it to be around 35mpg
Anyway, my real issue is that I have put about 400 miles on it and have begun to experience the following problem. It is getting more difficult to start after it has set and is at ambient temperature, maybe 40 F. It just turns over and over. In order to get it to start I have to hold the gas pedal down and turn the key, It will then start but I have to work the pedal just right and rev it just to get it to stay running. After that it will run ok when driving but when I idle at the first few stop lights then press the gas to go it wants to hesitate and (so far) almost die. It does that briefly then takes off.
Some other information: After I bought the car it did set for about 4 months with very little driving, but it always would start up when I did occasionally drive it. I then recently filled the tank and drove it until the low fuel light came on in order to verify the light worked and to see what kind of mileage it was getting.
To help this issue I just put in a new air filter and spark plugs but that did not help at all. After changing the spark plugs I started it (had to fight it to get running) and it ran in idle for about 10 minutes and there was more than normal amount of exhaust smoke the entire time (idle around 1K rpm). I then took it for a 15 minute test drive and parked it again and ran it at idle (still 1K rpm) but there was no visible smoke. I stopped and started the engine 2 or 3 times while it was warm and it starts with no issue when warmed up.
So my question is..
1) What can I do to make it start reliably when at ambient temp
2) What will stop it from hesitating and almost dying at stop lights (when hit gas) before it is fully warmed up?
3) Why would it have so much vibration from the engine? Top engine mount?
4) Why does it idle at 1000 rpm when the spec is 500-600.
Since I posed the questions above I have changed the fuel filter. No difference.
I have done a fuel pressure test at the Schrader valve; it was 34psi (spec 31-36) so it is good.
A pressure decay test (5 minutes after car shut off) it was still 34psi. So this is good.
Checked voltage on Idle Air Control = 10.99Vdc (spec 1.5 – 10.5) Assume this is OK?
Removed and cleaned the throttle body, the “butterfly” valve in the throttle body, the three vacuum ports, and the pintle and seat on the Idle air control valve. All these had a lot of black soot on the intake manifold side of the butterfly valve. The side of the throttle body from the air filter was clean. I did all this and now the starting issue and the hesitation/idle issue when accelerate from stop actually seem worse.
I also used a screwdriver to listen to the 4 injectors, I can hear them all clicking, though one does not seem as loud but it is on the passenger side of engine where vibration is worse.