Hi guys thanks for the add to the group. I’m having a real hard time trying to figure out what’s wrong with my 2008 GMC Yukon XL 5.3 4 x 4. I have a slight miss but no codes. I replaced everything in the evap system. Purge valve. Charcoal canister. Vapor canister vent valve. (Pump at gas station kept stopping while filling up). I tried a new throttle body. No change. I put new air filter in. I have a smoke machine. I have a creader scanner 123E. Any help would be greatly appreciated.
Slight miss but 6 mpg!!? Need help
- Thread starter Chetty mo
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- bad gas mileage
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With your scanner, monitor and document your short- and long-term fuel trims at idle and at about 1500 rpm.
Also, when it's warmed up a little check that the upstream O2 sensors (B1S1, B2S1) are switching from about 0.1v to 0.9v.
Check your misfire counters; a decent scanner will have a counter for each cylinder.
Also, when it's warmed up a little check that the upstream O2 sensors (B1S1, B2S1) are switching from about 0.1v to 0.9v.
Check your misfire counters; a decent scanner will have a counter for each cylinder.
Yes I have been taking my scanner with me on my landscaping route and watching the fuel trims. They look fine. My o2’s also look fine at about 750 to 850. I added a pic of something I don’t understand. The throttle position numbers in the red.
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Also not showing anything for the misfire data. 0 which seems odd since I can feel it when accelerating and while sitting at a light. But not all the time very intermittent.
Hi guys thanks for the add to the group. I’m having a real hard time trying to figure out what’s wrong with my 2008 GMC Yukon XL 5.3 4 x 4. I have a slight miss but no codes. I replaced everything in the evap system. Purge valve. Charcoal canister. Vapor canister vent valve. (Pump at gas station kept stopping while filling up). I tried a new throttle body. No change. I put new air filter in. New throttle body sensor. I have a smoke machine. I have a creader scanner 123E. Any help would be greatly appreciated.
Do you have the ability to read fuel trims and O2 sensor values?
Yes I have a decent scanner.
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Looks like it's been running a little rich. Besides the suggestions that @wjburken had, have you checked the fuel pressure, key on - engine off, and with it running?
EDIT: can you graph B1S1 to see how much it's moving? Has the MAF been cleaned lately?
EDIT: can you graph B1S1 to see how much it's moving? Has the MAF been cleaned lately?
CaptainAmerica1
Full Access Member
How old are the plugs? How bout the wires?
CaptainAmerica1
Full Access Member
Air pressure in the tires? New air filter lately?
Yes cleaned Maf. Ordered new one. Yes that o2 goes from .1 to .9
Fuel pressure is at 48 when at idle. 58 when off then turn key to on position
davidavidd
Member
I imagine you already did it but: new spark plugs, wires and coils?
They were on it when we got it about 4 years ago. Might be time to upgrade.
What caused you to install the new throttle body and throttle position sensor? Anything particular or were you just pulling the trigger on the parts cannon? Not throwing stones, but it’s always good to know what, if anything, drive previous decisions.
Tonyv__
Full Access Member
Read if you dare.
It doesn’t get good until the bottom of page 9. I hope this isn’t your issue but it was for me. Wiped out lifter and camshaft. I tried to diagnose everything before I tore into the engine. I also had a slight miss only at idle and accelerating from idle
www.tahoeyukonforum.com
It doesn’t get good until the bottom of page 9. I hope this isn’t your issue but it was for me. Wiped out lifter and camshaft. I tried to diagnose everything before I tore into the engine. I also had a slight miss only at idle and accelerating from idle
SOLVED: Another misfire chasing threads (2008 express van)
Details 2008 Chevy express 3500 cargo van 6.0 58k miles. 8k running hours. No service history So after last weeks fun with the wife’s MB. (I think it’s resolved). my work van started having a rough idle. Code reader says P0307 misfire cylinder 7 confirmed. So I went and changed out the...
www.tahoeyukonforum.com
My scanner is showing in red some values for the throttle position sensor. Position A and B. And absolute throttle position at 5.8% at idle.
