Reduced Engine power

[Bigtex93]

Need suggestions 2003 yukon 5.3

initially these codes came up
po101
po171
po220
po300

Checked throttle body harness...ok
Cleaned throttle body
ran fuel cleaner through
changed o2 sensors
changed fuel filter
changed air filter
Checked ground wires

Reduce Engine Power light still comes on and goes to limp mode
Also note RPM's bouces 500 to 1000 at idle
only codes now are
po171
po174

Suggestions?

[danielsatur]

Good job!
You probably weeded out a few problems with filters + cleaning.
1) Check the plastic, seals, and rubber on your PCV system, any unmetered air leaks will cause lean codes.
2) Don't forget to clean your MAF/IACT sensors.

[Bigtex93]

Originally Posted by danielsatur

Good job!
You probably weeded out a few problems with filters + cleaning.
1) Check the plastic, seals, and rubber on your PCV system, any unmetered air leaks will cause lean codes.
2) Don't forget to clean your MAF/IACT sensors.

Unmetered air leaks? How do you determine this....All my work has been researched on this board...do I need to take it in to a shop? apprx. cost

Also would a faulty plug cause these codes?

PCV system? location?

[danielsatur]

A smoke test is usually done at a shop, they blow smoke through the Air box, duct work, intake, EGR, and PCV systems to find air leaks.

Any unmeterd air leaks will confuse your ECU/PCU, the Air/fuel mix will be calculated wrong, thus lean codes will be thrown.


A backyard Tech, or mechanic will use brake cleaner, or starting fluid, while the engine is running. The rise in RPM's tells you that there's an air leak.
The EGR + PCV systems are the most probable cause, because of rubber, plastic, and seals leaking air.

The Positive crankcase ventilation (PCV) consist of a PCV valve, and tubing going from the valve cover to the air duct work on throttle body.

COST ?
I heard of a dude being charged $3.5k for a problem that wasn't fixed, it was a bad fuel filter.

[Bigtex93]

Originally Posted by danielsatur

A smoke test is usually done at a shop, they blow smoke through the Air box, duct work, intake, EGR, and PCV systems to find air leaks.

Any unmeterd air leaks will confuse your ECU/PCU, the Air/fuel mix will be calculated wrong, thus lean codes will be thrown.


A backyard Tech, or mechanic will use brake cleaner, or starting fluid, while the engine is running. The rise in RPM's tells you that there's an air leak.
The EGR + PCV systems are the most probable cause, because of rubber, plastic, and seals leaking air.

The Positive crankcase ventilation (PCV) consist of a PCV valve, and tubing going from the valve cover to the air duct work on throttle body.

COST ?
I heard of a dude being charged $3.5k for a problem that wasn't fixed, it was a bad fuel filter.

Thanks for the tip....pcv valve extemely dirty..changed out..don't know if this will help

also sprayed Carb cleaner around intake, no increase in RPM...any suggestions on other places to spray? Thanks

[danielsatur]

After cleaning PCV garment, valve, and tubing, use the spray to check for unmetered air leaks on the whole PCV system going to your Air duct work .. just like your intake!

Any rise in RPM's means there' a leak, use intake sealent for air leaks.

Also check for unmetered air leaks from Air box, duck work to your throttle body. All clips, and clamps should be tight.

All air is metered by the MAF sensor, and any leaks could cause your lean codes.

Reset and clear code, so the computer forgets.

Did you clean the MAF/IACT sensor with CRC MAF sensor cleaner?

[Bigtex93]

Originally Posted by danielsatur

After cleaning PCV garment, valve, and tubing, use the spray to check for unmetered air leaks on the whole PCV system going to your Air duct work .. just like your intake!

Any rise in RPM's means there' a leak, use intake sealent for air leaks.

Also check for unmetered air leaks from Air box, duck work to your throttle body. All clips, and clamps should be tight.

All air is metered by the MAF sensor, and any leaks could cause your lean codes.

Reset and clear code, so the computer forgets.

Did you clean the MAF/IACT sensor with CRC MAF sensor cleaner?

Could these codes (too lean) remaining, cause the truck to go into Limp mode?

for example..a intake leak....would that set off the reduced engine power?

[danielsatur]

I would focus working on the codes 1st, the reduced power mode is to protect you + truck.

The computer detected a problem, and put the engine into a reduced power mode.
A drive-by-wire system with a bad signal could cause a reduced power mode. The electronic signal from the gas pedal to the electronic throttle body was lost.

After checking for unmeterd air leaks on your Intake, Pcv, and Egr systems, need to clean
MAF/IACT sensors, and reset codes.

If this doesn't fix the problem:
1) Get a professional smoke test done, for unmetered air leaks.
2) New MAF/IACT sensor
3) New Upstream H02 sensors.

www.youtube.com/watch?v=FfiQ7qWiG-M

or

Do a Google ''Youtube DIY Auto Scotty cigar'

[Bigtex93]

Originally Posted by danielsatur

I would focus working on the codes 1st, the reduced power mode is to protect you + truck.

The computer detected a problem, and put the engine into a reduced power mode.
A drive-by-wire system with a bad signal could cause a reduced power mode. The electronic signal from the gas pedal to the electronic throttle body was lost.

After checking for unmeterd air leaks on your Intake, Pcv, and Egr systems, need to clean
MAF/IACT sensors, and reset codes.

If this doesn't fix the problem:
1) Get a professional smoke test done, for unmetered air leaks.
2) New MAF/IACT sensor
3) New Upstream H02 sensors.

Couldn't get much done today, too freaking cold in KC..lol

Cleaned maf..look ok

Did carb cleaner test along intake...half way down(leftside driverside)heard a lite whistle sound but the rpm went down..engine stumbled a little..Does that sound like a gasket problem?

[danielsatur]

Bingo! It sounds like you found the unmetered air leak.
I wonder, can you fix this problem for the short with a bead of intake sealent or epoxy putty?
Reset and clear code.

Do a Google on ''Yukon Intake leak'' 55k hits
It looks like, theres a new and improved Intake gasket for $90.
Caution - If you wait too long, the lean cond could cause the Intake to warp..

[Bigtex93]

how difficult is it to replace intake gasket?...glanced at it and it looks a little complicated around the fuel rails.

Any tips would be appreciated

[danielsatur]

I would start with getting two appraisals, and make sure it's a bad Intake gasket.

The fuel rail stays with the intake, the fuel lines are disconnected.

http://www.youtube.com Search ''how to replace a intake manifold''

[Bigtex93]

Originally Posted by danielsatur

I would start with getting two appraisals, and make sure it's a bad Intake gasket.

The fuel rail stays with the intake, the fuel lines are disconnected.

http://www.youtube.com Search ''how to replace a intake manifold''

Lack of confidence....having the shop do it....I hope this fixes everything...
I'll update once the job is completed.

[danielsatur]

Do a google ''Youtube Auto smoke test'' Intake, vacuum leak video's

I glad you decide to have someone do it, I would still get two appraisals for an Intake gasket replacement.

You probably saved $1k by doing the troubleshooting yourself, alot of shops like to troubleshoot at the customers expense.

[Bigtex93]

Originally Posted by danielsatur

Do a google ''Youtube Auto smoke test'' Intake, vacuum leak video's

I glad you decide to have someone do it, I would still get two appraisals for an Intake gasket replacement.

You probably saved $1k by doing the troubleshooting yourself, alot of shops like to troubleshoot at the customers expense.

Ok intake gasket replace...all codes clear...heading home engine light comes on....P1516....??? this was never on my original codes before I started this whole process...not what? Any Suggestions