Rough Cold Idle 2002 Yukon XL 5.3

Hi All,

This is my first post on the site in a while, so bear with me if I make errors...

Here is what I have:

2002 Yukon XL 5.3 with 73,381 miles. Battery replaced at 72,000 mile.

Currently have Extremely rough idle when cold and engine only ran a 15 minutes or so. I have minor rough idle when engine is totally warmed up and the vehicle has been running for over 1/2 hour. Appears to be getting worse as winter weather gets colder here in Nebraska. Have to have in neutral at stop lights...it jumps more than the race cam I had in the old Camaro.

(I do not remember it running rough after changing the battery, seemed to run smooth until about 4 weeks ago.)

Took advice from the forums and went to parts store to have the DTC codes read.

NAPA would not scan for codes.

Advance Auto Parts loaned me the Global OBDII code scanner to scan myself. Very easy to do.

This is what the printout said Verbatim:

Vehicle Scanned
General Motors
2000 and Newer
Global OBDII

DTC (CODES)

P0171
System to Lean
(Bank 1)

P0174
System to Lean
(Bank 2)

P0300
Random/Multiple
Cylinder
Misfire Detected

DTC Pending (Codes)

P0171
System to Lean
(Bank 1)

P0174
System to Lean
(Bank 2)

Now I am old carbuerator type of guy but have never worked on any of the newer engines and fuel injections, sensors, computers, etc. I knew what I could do to the old system when running lean or missing like this but need help now with this new code thing.

I have a new standard air filter. Original plugs and plug wires are on tight. I ran a bottle of injector cleaner through 2 tanks ago and if anything, it is worse when cold. This is an E-85 engine and about 6 months ago I ran about 4 tanks of E-85 through it, and it ran fine, quit using due to price vs. gas mileage drop.

Have been running unleaded or gasohol since new. I have bought about 4 tanks of gas from a new gas station with the first tank put in about 3 weeks after the station opened during the last 1000 miles. Last two tanks have not been from there.

Can some of the knowledgable ones tell me what I need to do? I saw a post on the GM forum from a year ago that mentioned needing intake manifold gaskets, which if that is the case is way beyond my abilities.

If it is a case of cleaning the throttle body, can someone explain how to do that exactly...I did buy a Haynes repair manual and at least now know what the throttle body looks like. But I am not clear about what to do or what to take off to get to it.

I did read in one post where you run the engine while this sea foam is being used but did not read that in others. So I am confused as to how to perform the process or is throttle body not the problem?

With this info I have shared, can anyone give me any advice? I will be off line until later but will get or share any more info needed.

Thank you in advance...Mike McCann

To me this sounds like a fuel problem. To start off easy and cheap, when was the last time you changed your fuel filter?

This problem could be the fuel filter being clogged, fuel pump going bad, bad fuel pressure regulator, bad or clogged fuel injectors.

I have a 96 Yukon and I had a similar problem. When the engine was cold, it idle rough and throw missfire codes, but as the engine warmed up, things got better. But as the cold weather approached, the problem got even worse to where the problem would not go away. In may case, the problem turned out to be clogged fuel injectors.

For the 96 model year including other model years, the fuel injectors where known to be a CFI system. The actual fuel injectors them selves were centrally located with pipping running to each cylinder. At the end of the pipping there are nozzels called "poppet" nozzels. The nozzels have been known to clog to where over he counter injector cleaner would not work. There is a TSB covering the proper cleaning procedure to be done by the dealer. The procedure is not guaranteed to fix the problem. If the cleaning does not work, the next thing was to replace the injectors with an improved design.

Having said all this, I don't know if the 2002 model year falls into this category of CFI fuel injectors, but hopefully this might point you in the right direction to fix you problem.

Omar

Hi Omar,

Yeah, I am/was thinking fuel injectors. The post response I have gotten on the gmc site lead me to believe that it is a dirty throttle body. So I am going to do things in this order...clean the throttle body, change the fuel filter, and clean the injectors ...I will probably do all three just because of mileage...I might even throw in a set of new plugs and wires.

I am going to drive it in between each of the repairs/changes to see if it is a specific item and then will report back what I found out.

It is so friggin cold here right now I am not inclined to be in the garage for long...it is so cold with rough icy roads that one of the plastic brackets on my fog lamp snapped in two and left the light just hanging by the wires. A high quality plastic bracket worth about...oh 15 cents but will probably cost about $20.

If I wanted to live in Siberia, I would move there...HA! And 3 weeks ago I was whining because it was too hot for deer season!!

Thanks for your thoughts...Mike

Hi All,

Went to Advance Auto and got a can of CRC Throttle Body cleaner for $3.66 including tax.

Loosened the big hose clamp and wiggled off the air cleaner to expose the throttle body opening. Sprayed and cleaned the butterfly and surrounding areas and put back together. 15 minutes total.

Truck runs like a champ. No surging or rough idle and the service engine light is off.

Now that is what I call an easy fix.

My only complaint? Not enough action on this forum. I had about 5 responses on gm-truck.com forum.

Now the Jeep forum on automotiveforum.com is great.

Not sure why the gmc forum here is a little light...is there other gmc sites out there?

Anyway, I hope this helps someone else...it is a hckuva lot cheaper than taking it to the repair shop.

Mike