P0300 Fault and Freeze Frame

daewoo
nubira

#1

Hi All,
I have a question that I am struggling to find an answer for, I have a 2005 Holden Viva which is basically a rebadged Daewoo Lacetti/Nubira. I have a fault coming up of P0300 on my OBDII reader, the freeze frame has the following information;

FUELSYS1 CL
FUELSYS2 N/A
LOAD_PCT 17.6%
ECT 84C
SHRTFT1 -1.6%
SHRTFT3 -40%
LONGFT1 0.0%
LONGFT3 -38%
MAP 25.0kPA
RPM 1904
KPH 0
IGN 36.5
IAT 27C
TP 12.2%

What would these numbers indicate? I have changed the coil pack, spark plugs, injectors and fuel filter. The way I am going I will end up changing the whole car and still not find the fault.

Any help would be much appreciated


#2

Is it actually misfiring? If it’s not actually misfiring there may be a PCM update. If it is misfiring,don’t forget the basics. Is compression the same in all cylinders?


#3

The short term and long term fuel trims are way out of spec.
They should be no more than +/- 20%. The negative numbers mean the computer thinks it’s getting too much gas.
Does this engine have a fuel pressure regulator with a vacuum hose?
If so pull the hose and see if it has gas in it. Would mean the regulator is leaking fuel into the manifold.


#4

Funny enough it doesnt seem to be misfiring, it seems to run better than it has before. I need to do a compression test to rule that out also.


#5

The fuel rail only seems to have a line in and no line out so not sure how it returns to the tank, I will do a fuel pressure test and leak down test and hopefully rule that out. When i turn the ignition on i can here the fuel pump running and when i remove fuel pump fuse the car dies pretty much straight away. I am going to look for the pressure regulator, maybe its away from the fuel rail hiding somewhere


#6

If this is a returnless system the pressure regulator is in the gas tank with the pump.
Anyway, something is making the engine run too rich, or making the computer think it’s too rich.


#7

Not uncommon:

http://www.aa1car.com/library/returnless_efi.htm


#8

My guess, either something wrong with an O2 sensor, or the MAP sensor. FWIW, here’s what some of those readings mean …

FUELSYS1 CL
FUELSYS2 N/A

not sure what that wording about two fuel systems means

LOAD_PCT 17.6% — this means the engine is load is 17.6%, idling probably

ECT 84C – that’s the engine coolant temperature, around 185 degrees F, ok

SHRTFT1 -1.6%
SHRTFT3 -40%
LONGFT1 0.0%
LONGFT3 -38%

the above are the fuel trims, in %. Not sure what the 1 and 3’s mean. The problem appears in the 3 circuit. Negative values means the computer is having to reduce the amount of fuel it is injecting compared to what it thinks would be necessary based on the MAP, IAT, and ECT readings. The O2 sensor is disagreeing, saying if it injects that much gas, it creates a bunch of raw gas coming out the tailpipe. the readings with an “S” in the front are short term fuel trims, and the “L” ones are long term. The long term reading of -38% is the one that needs fixing first. That’s the high priority here.

MAP 25.0kPA – that’s the intake manifold pressure reading. Atmosphere is 101 kPA at sea level, so that’s a vacuum of around 1/4 of atmosphere. Atmosphere is about 30 inches of mercury, so that’s a vacuum reading of 3/4 * 30 or maybe 18 inches of mercury as would normally be displaced on a typical mechanic’s gauge, about right at idle. May be slightly less vacuum that would be expected in a new engine. But still ok.

RPM 1904 – sort of high for an idle rpm
KPH 0 – vehicle speed probably, not moving b/c at idle
IGN 36.5 – not sure what that means
IAT 27C – intake air temp, the weatherman air temp at the time, ok
TP 12.2% – throttle position, meaning it is 12.2% open, about normal at idle


#9

I wonder if that means the ignition advance, 36.5 degrees? If so, that’s considerably more advanced than I’d expect at idle. My truck is spec’d at 6 degrees, and my Corolla is 10 degrees, both at idle. That far advanced though at idle, I’d expect you to have some drivability symptoms.


#10

Cheers George, I have done a compression test and have 175psi in each cylinder. I found the return vacuum line for the fuel system, doesnt smell like fuel and when I take it off you can hear the suction and the engine changes. I have bitten the bullet and taking it to a specialist to see if they can pick up anything.


#11

Have you considered the crank position sensor?


#12

But would a faulty crank sensor cause a -40% fuel trim reading? With no indications of a misfire observed by the driver other than the check engine light turning on with an 0300 code?

Could be, but to me seems more likely to be a problem among

  • MAP sensor
  • O2 sensor
  • Fuel rail pressure
  • Fuel injectors sticking
  • Wiring harness , including grounds
  • Engine computer fault
  • The ignition timing is really 36 degree advanced at idle
  • Vacuum leak