Hey everyone, I have a 2003 H2, 143,000 miles, been running great, a week or so ago, it fell flat on its face, no power, hardly able to go over 20 mph or so. Check Engine flashing.

I have my own scanner and have been a mechanic for a long time.

Checked the codes

I was receiving P0300, Random Misfires,

P0137 Heated oxygen sensor (HO2S) 2, bank 1 -low voltage

P0101 Mass air flow (MAF) sensor/volume air flow (VAF) . sensor circuit malfunction

I am guessing that all the codes stem from a lean condition from the misfires.

So I replaced the Plugs, Wires and coils, and the MAF just for the heck of it,

Drove the truck, still receiving the P0300 code.

Checked the real time data with the truck running and almost all the cylinders are misfiring.

Wondering if anyone has the parameters for the fuel injectors when the car is running to check and see what the actual fuel injector data is.

not sure what the next step would be, not sure what the ECM considers a misfire, as its not giving me a actual numeric coil number with the codes, or is a misfire a ignition stroke with no combustion, like a plugged injector or a injector that's not spaying enough or too much.

Thanks

 

Possibly clogged cats? With everything misfiring its certainly a possibility and your cats are the originals they are not very young anymore.

Could also be fuel pressure which would either be the regulator on the fuel rail on the drivers side of the intake, or the pump itself which means dropping the fuel tank. Need a fuel pressure gauge to verify fuel pressure on the rails (test port on the passenger side rail) but not sure if they will tell any info about the vacuum actuated regulator on the other side.

Anyways with misfires on all cylinders its not likely a plugged injector as that would only cause problems on the one cylinder unless its bad gas or some sort of contamination in the gas. As it happens, our 2003 models DO have an inline fuel filter as well which if clogged can also cause these issues.

 

Plugged cats would also be my guess. I have an OTC exhaust backpressure gauge that screws into an 02 sensor bung. It makes it really easy to diagnosis a bad cat.

Drive over and we can do a test on them.

 

yep dealer diagnosed it as bad cats, Phil where did you get the back pressure guage?

 

I have had it since the 90's. I bought it from the Cornwell tool truck. They sell OTC brand equipment.

 

I had the exact same thing last year.

Make sure the intake tube is properly sealed / fitted on the bottom side of the throttle body. They have a tendency to curl in on the bottom and effect the MAF. Also check that the arrows at the MAF are aligned.

If it runs better with the MAF unplugged, replace the MAF.

Tim

 

Right off the bat remove the O2 sensors on both banks if you suspect plugged exhaust. That will tell you if it runs better the cats are plugged up. Check your scanner under missfire and see if the miss fire is less as well. Make sure also that your fuel pressure is up to spec. 60-66psi but never less than 50psi The deal with lower fuel pressure is that it gives all the indications of lean missfire everytime. Check also the fuel filter as well..remove it and drain it and wipe off one end...you should be able to blow thru it easily and spray gas out of it. If you can - the filter is fine.
Check the basic always first....