Hello all ,I am not only new here but also to chevy ownership in general as i have always had explorers before this but the chevy just seemed bigger and more robust. I now have 2 blazers but seem to have the same problem with both. the newer one is lpg converted if that makes a difference whereas the older on is not. Both trucks have been pressure tested with all cylinders being around the same , they have had new plugs,leads and caps, both have new maf sensors and have been fully serviced BUT both have a missfire and use a stupid amount of fuel had problems with getting both through mot both due to very high emissions and they also seem to kick out a lot of black substance from the exhaust could be oil or coke not sure which it does not smell of oil and neither vehicle seem to use a larger than expected amount of oil. there is no sign of head gasket problem and both run well with plenty of power when not missfiring the garage i bought them from said it was an ecu problem but they could not read any fault codes from it as they said their kit could not communicate with it. Can anyone with more experience please shed any light on this as I just dont know where to look next, could it be anything to do with the cat and is there any way of cleaning the cat to stop some of the sooty discharge? thank you in advance ian

 

We'll need information on the Blazers you have, Year, # doors, 2WD/4WD etc.

However, it sounds like what you might have is an over-rich/flood condition (i.e. too much fuel). Does the engine oil smell like gasoline? Are you getting O2 sensor errors?

 

i'm in the exact same boat.
i drive a 03 Ls with a 4.3 and I've got the same problems.
nobody can tell me what it is.
only code thrown is multiple misfires.
don't know what to do other than get 12 mpg.
sucks...

 

sorry didnt think those details would make a difference but both are 4 door 4 wheel drive auto one is 99 and the other is 2001 both rhd, the older one has now actually backfired hard enough to blow the exhaust box apart, the high emissions confuse me it's almost as if the cat is full of oil but the cars do not use any oil so it can't be that but I am getting about 9 mpg on either gas or petrol it's getting ridiculous I like these trucks as they are comfortable but I just can't afford to run it like this and have even advertised the older oe now as for spares or repairs

and no the oil doesn't smell like petrol but the exhaust fumes smell like nearly neat fuel
thank you will look

 

just to be a pain in the proverbial i have just had the autogas fixed to combat the high fuel usage and emissions and they have also diagnosed a fault reading o2 sensor bank 1 faulty I have a new sensor but which is bank 1? can anyone shed some light please

 

 

thank you all for those replies but here we are again, I have replaced both o2 sensors and run a cataclean car seems to be running better but still has a missfire on hard acceleration and espite the new o2 sensors I am still getting the same results on obd reader , every time it says bank 1 sensor 1 low voltage .. any ideas gratefully received

 

When my fuel injection system sprang a leak, it was dumping fuel directly into the intake ports. This caused O2 sensor faults. I would do a pressure check on the fuel system. Other threads can be found that go through the details of the process. It is pretty easy and not a very dirty job.

 

thank you will look for other threads