SavedByGrace
Member
Hi all - been trying to diagnose my 8mpg issue on my 03 hemi 5.7.. reringed and new timing set 20k miles back at 100k - everything inside was brand new looking and perfectly in spec(i bought it with a spun rod bearing).
Trying to chase low power and terrible mpg:
20k miles back:
New rings & bearings, exh gaskets and bolts (no leaks)
New timing set + new NGK factory plugs (NOT iridium)
Last 6 months:
Cleaned throttle body
New cat 1000 miles back (no change)
Retorqued knock sensors to 15 ft lbs
Checked fuel psi (49)
Replaced air sensors (IAT and MAP twist one)
I rechecked trans fluid yesterday idling in N and its clean red (has 20k miles on it) -
P0113 code:
Now ive never had a CEL - and the truck has passed smog everytime, however yesterday I did the 3 key switch and got P0113 - which is the IAT sensor, so I followed the manual to the tee and no issue, first I read 4.6k ohms resistance between the ground terminal and the engine ground, then I measured between the 2 pins and got almost the same reading (manual says it should not be under 100 ohms - but 4.6k seems excessively high?). I then proceeded to short the terminals out and got 240 degrees, then I unplugged it and the temp dropped to -40c which indicates the wiring AND sensor are functioning according to forums - plugged in and running it showed the IAT around 31c which I believe to be a little warmer, ambient was probably around 25 degrees- I then pulled the ECU plug and everything looked brand new inside - I sprayed it with elec corrosion protection in any case and popped it back together.
Timing?
So I plugged in an obd sensor to see what was going on yesterday and noticed super ******** ignition timing! 10-24 ATDC!! Is this possible or is the OBD unit faulty?
Here is a shot of the timing low/high cruising around town- yesterday I did notice it more like 5-15 but not sure if that was btdc or not.. fwiw the truck seems to drive ok -but when I tow is embarrassing - even a small 18ft boat makes it hardly accelerate up a turnpike ramp :/ it just makes a noise upfront but not much happening to the wheels!
Anything look out of whack?
Trying to chase low power and terrible mpg:
20k miles back:
New rings & bearings, exh gaskets and bolts (no leaks)
New timing set + new NGK factory plugs (NOT iridium)
Last 6 months:
Cleaned throttle body
New cat 1000 miles back (no change)
Retorqued knock sensors to 15 ft lbs
Checked fuel psi (49)
Replaced air sensors (IAT and MAP twist one)
I rechecked trans fluid yesterday idling in N and its clean red (has 20k miles on it) -
P0113 code:
Now ive never had a CEL - and the truck has passed smog everytime, however yesterday I did the 3 key switch and got P0113 - which is the IAT sensor, so I followed the manual to the tee and no issue, first I read 4.6k ohms resistance between the ground terminal and the engine ground, then I measured between the 2 pins and got almost the same reading (manual says it should not be under 100 ohms - but 4.6k seems excessively high?). I then proceeded to short the terminals out and got 240 degrees, then I unplugged it and the temp dropped to -40c which indicates the wiring AND sensor are functioning according to forums - plugged in and running it showed the IAT around 31c which I believe to be a little warmer, ambient was probably around 25 degrees- I then pulled the ECU plug and everything looked brand new inside - I sprayed it with elec corrosion protection in any case and popped it back together.
Timing?
So I plugged in an obd sensor to see what was going on yesterday and noticed super ******** ignition timing! 10-24 ATDC!! Is this possible or is the OBD unit faulty?
Here is a shot of the timing low/high cruising around town- yesterday I did notice it more like 5-15 but not sure if that was btdc or not.. fwiw the truck seems to drive ok -but when I tow is embarrassing - even a small 18ft boat makes it hardly accelerate up a turnpike ramp :/ it just makes a noise upfront but not much happening to the wheels!
Anything look out of whack?
