I have a 1998 Saturn SW1 with the SOHC engine. Sometimes the car refuses to start. The only way to start it is to depress the gas pedal. I replaced the battery and the starter when I first got it.
I recently replaced the spark plugs and wires. Found the No.4 plug is covered with dark stuff. The #4 injector is all wet. The other 3 are fine. I am not sure if the injector is covered in oil or fuel, since the oil cap is right in front of it.
Because the injectors are a bit expensive and the previous owner told me he already had the fuel filter replaced, I decided to do a fuel pressure test. I am not sure what are some good numbers for this vehicle but the readings I got was: around 50+ psi with the key on and engine off. 70ish psi with the engine idling.
I also read that the fuel pressure regulator is inside the filter itself. I would like some advice on what I should do in this case?
You might start with compression test of all cylinders, #4 might be bad.
Possible #4 isn’t firing but that should set a CEL code.
As far as starting, Throttle Position Sensor?
Those fuel pressure numbers seem pretty normal, doubt the problem is fuel pressure. Your problem could be a leaky injector. The injectors are only supposed to spray fuel on command of the computer, but sometimes one will get stuck in the “on” position and spray all the time. This would normally show up in a fuel pressure hold test, where you pressurize the fuel rail then turn everything off and monitor the fuel rail pressure over time. Another test to consider is a fuel trim test. That would tell you if the engine is running overly lean or overly rich. A leaking injector would usually cause it to run overly rich at idle. Wet fuel at the tip of a spark plug could also be caused by that spark plug not firing, and should be considered too. Faulty ignition coil for example.
If I am not mistaken this engine is the old GM “Quad Four”… It uses that one piece cover over all the spark plugs and has a Ignition Control Module that is well known to cause these issues…and it will drive you nuts trying to diagnose it
Most likely cause of your issue is the Ignition Control module…next suspect is the crank sensor… But when the Init Control Module is starting to die… it mimics a bad crank sensor.
Next known issue is the security system not reading the key properly…
There have been VOLUMES written on the net about this engine and Ignition system and how to diagnose and repair it.
It has driven men and women greater than I to insanity with cruel regularity back in the day… so be forewarned. Muhu-hahaha
My LTFT numbers sit between -8 to -10. Can the coolant temperature sensor affect fuel trims and also cause a hard start condition? How do you test a fuel injector?
So… some people are saying the numbers at idle are fine and others are saying the numbers are high. How do I know for sure?
Today I grabbed a noid light kit. Injectors are firing correctly but I found the No.4 is indeed leaking. A lot of Saturn owners are suggesting me to replace the fuel filter. The pressure regulator is inside the filter.
I already ordered an IAC valve. Imma order the injectors now.
A rare mistake for you, Blackbird. Saturn designed is own 1.9 liter 4 cylinder in SOHC and DOHC configuations. Not related to the Quad 4. This car doesn’t have the ignition cassette. It has a coil pack.
They told me to replace the filter too because they considered 70 psi on idle to be too high for this car. Hmm okay I couldn’t order the filter anyways. Out of stock. So injector first.
Oops… LOL… This must be my week for mistakes. Thankfully they are only online here in front of all of you and not in the “real world” this week. Lets see what next week brings…always plenty of time to screw up in a real way… LOL
The later Saturns had the setup I was referring to… perhaps it was 00’ and up… I don’t know I forget this stuff man. Q4 was definitely in the later model years, no question about that. I do however recall the engine in question here, I wasn’t thinking far enough back I guess… Apologies.
Negative 10% fuel trim numbers means the computer has determined the mixture is too rich (based on the O2 sensor) and is cutting the fuel rate back by 10% compared to what the MAF sensor (among others) is suggesting the fuel rate should be. Common reasons for negative fuel trims
Fuel rail pressure is too high
Fuel injector(s) is faulty, injecting too much fuel
Engine coolant temp (ECT) sensor is faulty, telling computer engine is cooler than it actually is
MAF sensor is faulty or dirty, telling computer the air flow into the engine is more than it actually is
Faulty O2 sensor
Of the 5 above, a dirty MAF sensor seems to be the most likely cause for something like this, according to the posts we get here. Not saying that’s the reason for your problem. Just saying.
Fuel injectors are usually tested first with a fuel injector balance test. Basically the shop will pressurize the fuel rail, then pulse the first injector 20 times (say), and measure how much the pressure drops. Then they’ll re-pressurize and do the same test on injector number 2, then 3, then 4.
They’ll end up with a set of data for the four injectors, how much the fuel pressure dropped for each; an example: Inj 1 = 10 psi, Inj 2 = 10 psi, Inj 3 = 10 psi, Inj 4 = 15 psi. That would mean injector 4 is injecting 50% more fuel than injectors 1-3.
