Hello all. I have been member for quite some time, but never really needed help with anything serious. Until now of course.
Situation:
2002 Yukon XL, 5.3 flex fuel, trouble code p0300, sometimes another p03xx.
Replaced stuff:
Plugs, wires, coils, injectors, maf, both front o2 sensors.
Symptom: Rough idle, lack of power, really bad mpg.
When I replaced the maf today, I forgot to put the connector back on and started to drive around until it got into closed loop (autoXray ez6000).
Before and after, it already started stumbling when I put a light load on it. I only accelerated up to about 1500-1800 rpm and up to about 30-40 mph. During all this, I had the computer hooked up and kept an eye on the misfires, not a single one.
Long term fuel trim was at 128, rich/lean ratio at 0, AF ratio at 14,2.
Short term fuel trims were at -4 to somewhere like -25%.
I could not really get it to go up in either speed or rpm, more than say 2000, without the engine protesting like hell (cats clogged?).
The weird thing here is that when I plugged in the maf connector and started the engine again, it showed almost instantly multiple misfires on almost every cylinder, with the engine behaving in the same way as before. The ses light came up this time as well, flashing.
Does somebody know if the ECM somehow can't produce troublecodes when the maf connector is disconnected???
A while back, at night, we checked to see if the cats were glowing when the engine was warm. Nothing to see there. This was after we had been pulling a car behind it. That road wasn't really flat, so it had to "work" a bit.
It has a tune from this diablo sports thingy. Problem is that I lost this damn thing, so I can't bring it back to original settings (this is probably why the AF ratio is where it is).
BTW, I'm in europe, so anything regarding to US automotive shops like NAPA and what not will not help here (reading troublecodes and more).
And yes, I did read pretty much any post about p0300 and other related stuff...
Thanks for any input.
Situation:
2002 Yukon XL, 5.3 flex fuel, trouble code p0300, sometimes another p03xx.
Replaced stuff:
Plugs, wires, coils, injectors, maf, both front o2 sensors.
Symptom: Rough idle, lack of power, really bad mpg.
When I replaced the maf today, I forgot to put the connector back on and started to drive around until it got into closed loop (autoXray ez6000).
Before and after, it already started stumbling when I put a light load on it. I only accelerated up to about 1500-1800 rpm and up to about 30-40 mph. During all this, I had the computer hooked up and kept an eye on the misfires, not a single one.
Long term fuel trim was at 128, rich/lean ratio at 0, AF ratio at 14,2.
Short term fuel trims were at -4 to somewhere like -25%.
I could not really get it to go up in either speed or rpm, more than say 2000, without the engine protesting like hell (cats clogged?).
The weird thing here is that when I plugged in the maf connector and started the engine again, it showed almost instantly multiple misfires on almost every cylinder, with the engine behaving in the same way as before. The ses light came up this time as well, flashing.
Does somebody know if the ECM somehow can't produce troublecodes when the maf connector is disconnected???
A while back, at night, we checked to see if the cats were glowing when the engine was warm. Nothing to see there. This was after we had been pulling a car behind it. That road wasn't really flat, so it had to "work" a bit.
It has a tune from this diablo sports thingy. Problem is that I lost this damn thing, so I can't bring it back to original settings (this is probably why the AF ratio is where it is).
BTW, I'm in europe, so anything regarding to US automotive shops like NAPA and what not will not help here (reading troublecodes and more).
And yes, I did read pretty much any post about p0300 and other related stuff...
Thanks for any input.
