Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
The truck has lean codes for both banks. Runs lean cold and hot. Also the idle is at about 550-600 RPM. Checked fuel pressure and has 60 PSI and doesnt drop at all on a snap throttle. Did an injector balance test and all injectors dropped from 57 down to 40 PSI across the board. O2 sensors respond to lean and rich conditions by disconnecting brake booster and spraying brake clean into the intake. all biased voltages are 447 mv before starting vehicle but as soon as they start heating up voltages drop down to 50-100mv. They have also been replaced because of prior O2 codes that have not returned since replacement. Performed a volumetric efficiency test and was 65%. Replaced MAF sensor because everything else seemed fine with a New Bluestreak brand from Autozone and did not change anything. Truck does not show any lack of power while driving it will burn the back tire off if you slam the accelerator. Also checked the purge valve for sticking open and works normal. Oil change was done as well. When raising the RPM the fuel trims go from 27+ on both banks up to 30+. We also cleaned the throttle body for the idle problem and did fix the low idle. This truck does not have a ICV and does not have a relearn function on the Snap Zeus scan tool. I am at a loss on what else to check. I figured if it was a mechanical problem I would have a loss of power but it runs normal while driving just idle low and runs lean on both banks per scan data.
Yes it did have a broken bolt on each side but you couldnt even hear an exhaust leak even when cold. And 30%+ seems way too high for an exhaust leak you cant even hear. I have seen these trucks with bigger exhaust leaks before and fuel trim were not any higher than 10 percent, 15 at max.
You could still have a vacuum leak along with fuel delivery problem. 5.3's are known for intake leaks. Worth doing smoke test and water on intake runners.
Voltage check on injectors with a DSO is very helpful but not all have the equipment.
If possible, pinch off fuel return line and watch for trim correction.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
Being wrong doesn't bother me, it's being right and not understanding why that does
Fuel pressure was steady at 60 PSI even upon snap throttle, indicating no sign of a fuel delivery problem. Also performed an injector balance test and all had 57 PSI to 40 PSI drop across the board. We used a smoke machine no leaks were indicated. Also tried brake clean around the manifold and no change in fuel trim or the O2 sensor voltages.
I tried looking for this data PID on 2 different scan tools and was not an option on this truck.
If this reply refers to the alcohol content you couldn't find: Get a fuel sample out of the tank. Put x volume of it together with y volume of water into a graduated measuring cup. There will be a distinctive line between the two different fluids. Then agitate the fluids and let them settle. Any alcohol in the fuel will rise the "water level" mark. Based on this you can calculate the percentage of alcohol in the fuel.
Otherwise you may want to run it with fresh, known good gas from an external source. As the fuel trims are skewed all the time you could test it even at idle in park.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 4 years 5 months ago by juergen.scholl.
The fix ended up being the MAF sensor they purchased a new OEM and it fixed the issue. This will be the last time i use an aftermarket MAF new or not on any vehicle.
Symptoms sure pointed to MAF but it was replaced... didn't recommend testing MAF voltages as you seem very apt and thorough. Lately have seen many many cases of aftermarket parts not compatible. Chrysler, Nissan and GM. What made you go for the MAF a second time?
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
Being wrong doesn't bother me, it's being right and not understanding why that does
It was a used car dealerships vehicle. He just took it to another shop because I communicated that I had no other options on what to check. And the other shop replaced the MAF and the idle is normal and fuel trim are back to normal range
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