08 Tahoe 258000 miles hard starting and wet spark plugs

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Jkiel84

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Yes I’ll get the trims and o2 voltage all the 02 sensors are brand new Bosch ones cause I thought it was the cats cause I got the code for the cats performing under threshold so I changed them and the cats looked good I also did a compression test lowest compression was 165 and the highest was 180 I did the pressure test to see if the head gasket was leaking and that was normal but I get a code now for the fuel pump command module that comes and goes I changed the plugs now it’ll start right up and all I get is a p0300 code I’m at a lose I’ll get the o2 sensor voltage and fuel trims and it’s never had e85 in it I’m the second owner and my boss was the first other thing it ran fine one day then the next it wouldn’t run at all unless I pushed on the gas pedal
 

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I can't see the PID descriptions, but if the g/s reading is for the MAF, and the truck is at idle, the MAF is over-reporting. Warmed up and at idle that value should be roughly equal to the engine displacement in liters (e.g., 5.3).
 
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This are the trims and o2 sensor values but it doesn’t seem like the trims are doing anything shouldn’t they fluctuate a little
 

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This are the trims and o2 sensor values but it doesn’t seem like the trims are doing anything shouldn’t they fluctuate a little

The LTFTs should have values in them unless they were recently reset. The STFTs would need to have the engine running for a bit and would start reporting once it warms up enough to go into Closed Loop. Something does seem to be wrong, with nothing being reported on either LT or ST.
 

j91z28d1

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somewhere on the scanner it should say if it's in closed loop. from those pics like said above.. the ecm isn't doing anything to correct any. and they always do something while in closed.
 
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I can't see the PID descriptions, but if the g/s reading is for the MAF, and the truck is at idle, the MAF is over-reporting. Warmed up and at idle that value should be roughly equal to the engine displacement in liters (e.g., 5.3).
It wasn’t quite warmed up yet it’s misfiring on four cylinders I’ll show you the misfire chart
I can't see the PID descriptions, but if the g/s reading is for the MAF, and the truck is at idle, the MAF is over-reporting. Warmed up and at idle that value should be roughly equal to the engine displacement in liters (e.g., 5.3).
it wasn’t quite warmed up it misfiring on 5 cylinders
 

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The LTFTs should have values in them unless they were recently reset. The STFTs would need to have the engine running for a bit and would start reporting once it warms up enough to go into Closed Loop. Something does seem to be wrong, with nothing being reported on either LT or ST.
It was close to warmed up I didn’t see if it was in close loop but I get codes saying all my o2 sensors have a problem but there brand new but it shows the o2 sensors are working
 
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Jkiel84

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Yes I’ll get the trims and o2 voltage all the 02 sensors are brand new Bosch ones cause I thought it was the cats cause I got the code for the cats performing under threshold so I changed them and the cats looked good I also did a compression test lowest compression was 165 and the highest was 180 I did the pressure test to see if the head gasket was leaking and that was normal but I get a code now for the fuel pump command module that comes and goes I changed the plugs now it’ll start right up and all I get is a p0300 code I’m at a lose I’ll get the o2 sensor voltage and fuel trims and it’s never had e85 in it I’m the second owner and my boss was the first other thing it ran fine one day then the next it wouldn’t run at all unless I pushed on the gas pedal
 
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If it’s been “barely running” the throttle body servo might be stuck barely open and is stopping it from running as it should (within reason)
an it everyday up until this point without a problem
 

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this is just a general rule but when looking at live misfire data, it will be counting up as it's missing. if it's just a value like 5 to 20 and not moving, work on the high and currently moving one first. I'm guessing you have a isses in cyl 8.


I'd have to look up the codes and what the ecm does when those specific o2 sensor codes are thrown, but it very well could stay in open loop if both front o2 sensors codes are set. might have to clear the codes before it will go into close loop. but look over the freeze frame data first if it has it that will be lost when cleared.


my 2 cents on o2 sensors is I'm not a fan of Bosch. but I'd hate to say change them if newish. Just keep in the back of your mind they could be fouled out like the spark plugs were. the obd codes usually have a : and then 2 more numbers that are more specific as to why it set the code if your scanner can see them. it could be as simple as the heater circuit fuse is popped and the got cold and fouled.
 

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