99yukon

Hey everyone I'm new to the forum and been having problems with my Yukon lately.my truck idles kind of rough but not terribly. it will drive fine up until 3/4 throttle. If i floor it will do okay under 3000 rpms but anything over that at WOT it will ping and my truck feels like it doesnt even move. it will rev up fine in park but ive i rev it past 4000 it will come back to idle with a misfire? Also if i take off from a stop at WOT it will do the same thing but it doesn't want to shift unless i let off the gas pedal .I have a p0430 code for bank 2 below threshold.truck has 165,000 miles. i have talked with about 5 other people with the similar problem They have all replaced there cats and o2 sensors and have not had a change. im tight on money so would really like to figure it out without wasting money.Ive already had the bank 2 cat replaced thinking that would help and of course it didn't. anyways it drives ok under normal driving. haven't checked my fuel pressure yet but im starting to think its my fuel pump.Any help would be Awesome. Thanks guys!

MDTAHOE

Sounds like a restricted fuel filter and or a bad fuel pump. It could be a problem with the Air Flow Meter however the other 2 problems are much more common.

99yukon

I just replaced my fuel filter about a week ago no real different notice in power.Also this may be helpful. I just got some freeze frame data at idle.

P0430-Catalyst System Efficiency Below Threshold (Bank 2)

Fuel System 1 Open Loop -Drive
Fuel System 2 Open Loop -Drive
Calculated Load 2.7%
Engine Coolant-181 Degrees
STFT Bank 1 -3.1%
LTFT Bank 1 3.9%
STFT Bank 2 -0.7%
LTFT Bank 2 1.5%
Intake Manifold Pressure 11.2 inH9
Engine RPM 562
Mass Airflow Sensor 000.91 LB/Min
Throttle Position Sensor 0.3%

This all ive recorded so far. I was thinking about driving over to my old school auto shop. They have a lot better testing wise computers which i could get more info off of.

MDTAHOE

What is the O2 sensor voltage while the problem is happening?

99yukon

how do i find that out? i was just using a cheap scanner from schucks and thats all i could get it to tell me.

99yukon

Checked fuel pressure.When I turned the key on it was at 60 PSI then started and idle is at 58 PSI if I rev it up the highest it would go was 62 PSI.Spark is fine.checked MAF looks fine but haven't cleaned it yet so not really sure about that. Coil is brand new as are Spark Plugs and wires.Plugs are gapped at .60 and are NGK. Wires are Duralast. New fuel filter and air filter as of last week.It really seems to do fine just any thing above 3500 and it hates it.Also noticed my throttle response has dropped since the problem.BTW my idle is not terrible just a little worse than normal.

in2pro

I'd be suspicious of the plugs and or wires not sure why you didn't go with the AC/Delco they are typically more reliable....

99yukon

All of these symptoms were happening way before the tune up and everything Ive replaced.I did a little research and found that my intake manifold pressure should be between 19 and 20 Inches/Hg. Mine is only 11.2 Inches HG. also looks like the shop replaced the cat on bank 1 when the whole time bank 2 was the bad cat. Its probably due for another cat anyway so I'll probably have that done soon along with the o2 sensors but i had a couple people telling me that if i replace the cats and theres something still wrong with the engine that my new cats can go bad again. I really hope i get it fixed soon before my new cat gos out again if thats the case.I do plan on changing the plugs to ac delcos but really doubt thats gonna help much since probelm was before the plugs.

MDTAHOE

Is that 11.2 at idle or reved up?

stopher2

so far everyone is addressing the inputs to the engine.

consider that the catalytic converter might be clogged and do some google'n on that.