Rough Idle-Have Codes

[Spin Bubba]

Hi All,

 

This is my first post on this site, so bear with me if I make errors

 

Here is what I have:

 

2002 Yukon XL 5.3 with 73,350 miles. Battery replaced at 72,000 mile.

 

Currently have Extremely rough idle when cold and some minor rough idle when warmed up. Appears to be getting worse as winter weather gets colder here in Nebraska. Have to have in neutral at lights...it jumps more than the old race cam I had in my old Camaro.

 

My situation is similar to other rough idle posts mentioned in the past few weeks by other owners.

 

(I do not remember it running rough after changing the battery until about 3 weeks ago.)

 

Took advice from this forum 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 and have never done anything in regards to 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.

 

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 gasahol since new. Bought about 4 tanks of gas from a new gas station about 3 weeks after it opened during this last 1000 miles.

 

Can some of the knowledgable ones tell me what I need to do? I saw a post 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 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.

 

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

 

Thank you in advance...Mike McCann

[Bish]

Sounds like the typical dirty Throttle Body and Idle Air Control Valve.

 

Pull off the intake pipint (from air filter to TB). Get some Throttle Body cleaner (has to be safe for TB as there is a coating on it). Open the buterfly valve by hand and spray everywhere. You should be able to see the dirty parts (all behind the blade). The IAC is a plunger type valve on the top passenger side of the TB. 2 torx screws and an electrical connection and is comes out. Hose it down with cleaner and wipe with rag.

 

There is a Idle Re-learn Procedure also. Block the wheels, make sure engine up to temp, start, put in drive for 5 minutes, put it in park for 5 minutes, done.

 

The Top Engine Clean is what the Seafoam is used for. I also do that every 30K or so. I pull the brake booster hose off and pour it through the booster while manually opening the TB to keep it running. THis will clean out the carbon. The Top Engine Clean quiets down my pinging but has little effect of idle so I'm not convinced this is your problem.

 

Let us know how it works out.

[Spin Bubba]

Thank you Bish,

 

I will give it a shot. Thank you for the advice.

 

Do you have a particular brand of cleaner you like?

 

As usual, my wife is nervous about me doing this but I am

pretty calm about it as she worries enough for both of us...HA!

 

Mike

[firstruck]

I use Sea-Foam deep creep for cleaning the TB. Never had a problem with it.

[Ape0r]

Sea Foam or GM Top Engine Cleaner will be fine. Sea Foam is available at most car parts stores, top engine cleaner will be available at most dealerships.

 

Sea Foam oughta cost less.

[busta]

If you have any cornhusker stickers, plates or anything like that then I would say that would be the problem...LOL j/k

[Bish]

Thank you Bish,

 

I will give it a shot.  Thank you for the advice.

 

Do you have a particular brand of cleaner you like?

 

As usual, my wife is nervous about me doing this but I am

pretty calm about it as she worries enough for both of us...HA!

 

Mike

 

<{POST_SNAPBACK}>

 

 

 

Although I use both Seafoam and GM Top Engine leaner in other places, I like to stick to TB approved cleaners. I just get whatever Throttle Body cleaner is at Napa (3M Brand???) or Autozone. Stay away from Carb cleaner as certain brands I know for a fact will eat the coating.

[Spin Bubba]

Hi All,

 

Thanks for all the advice.

 

Am heading to the Advance Auto Store now to get the Throttle Body cleaner. Figured they let me use their code reader, better give them the business. Will let you know the results when through, although may not be until Friday or Sunday due to work and family committments.

 

Mike ...hey busta, I am not sure I really live in Nebraska 'cause it looks and feels like Siberia!! yeah, I bleed Husker red and the Huskers throttle body has been a bit clogged the last few years as well! Ha

[Black Bart]

I just finished helping a freind repair his 2000 Tahoe a couple of hours

ago, he had the exact semptons you have idleing up and down when

cold, the colder the worse it was. codes po171, po174, po300.

 

It ended up being a leaking intake manifold gasket, gasket $35.00

and about 2 hours of labor.

 

Black Bart

[Spin Bubba]

Okay all,

 

I went and got got a spray can of CRC Throttle Body Cleaner for $3.44 at Advance Auto..with tax it was $3.66.

 

Loosened the huge hose clamp screw and wiggled off the air cleaner from the throttle body.

 

Did what I was told in posts as far as spraying it and wiping. Whole procedure took about 15 minutes.

 

Truck has run like a champ all evening. Check engine light is off and it feels like it has a heckuva lot more power.

 

$3.66 and the awesome advice of people who post here and on automotive forum.

 

How much would that have cost at the repair shop?

 

Used less than 1/4 of the can...am going to check into doing the TB on the jeep next and clean it up.

 

Thanks a ton everyone...will let you know if it pooches out and I have to do something else. Right now I think we might have got it!!

 

Mike

[00Tahoe]

http://www.gm-trucks.com/forums/index.php?...topic=25982&hl=

 

Read this post. I had the exact same problem as this thread starter. More than likely, you do to. His final fix was the intake manifold gasket. Guess what, that was my fix too after chasing it down for about a year and a half. Although cleaning the parts helped while your car was warm, I would be fairly certain that you still had an issue this morning when you started her up.

 

The fix is not that difficult, mostly disconnecting and reconnecting. The most time consuming part was cleaning the manifold and where it sits. Good luck with your endeavor.

 

BTW, I had the same exact codes 171, 174, 300. Seemed like everytime we kept resetting the SES light, it would trigger just as quickly. The problem was getting worse as time went on.

[Spin Bubba]

Hi All,

 

It is still running fine but I think I can detect a small shudder when it is totally cold although not each time. The optomist in me says I have found the problem and have solved it and the pessimest/realist in me says that you are right and it is the intake manifold.

 

I will run with it a while and see what happens and report back in a few weeks.

 

Thanks again for all the advice...at least I know the two fixes recommended...clean the throttle ody or change the Intake manifold gasket.

 

Mike