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Signs of an Intake Manifold leak!!!! 5.3L GMC

09-23-2007, 11:16 PM
I have a GMC Yukon XL 5.3 with a rough Idle only at a stop, it only has 56K on it. Could this be a intake manifold leak? Does anyone know the systoms of an intalke manifold leak. Please help

09-26-2007, 12:17 AM
Sounds like it might be a gasket. They are notorious for that! Check the backside of it. Had to do one on ours around 60-70K or so. Not too hard, just time consuming. Check tune-up stuff too, like cap, wires, filters, O2 sensors. O2 sensors can also cause idling to be rough, which will cause you to use more fuel. If it is leaking water, check water pump, hoses. Rear, could be gaskets. Good luck! Hope it works out for you! :)

09-27-2007, 10:47 AM
First a question: What year is your Yukon XL? The GM 5.3 liter engine is a distributorless ignition setup, and has a single ignition coil per spark plug. (coil near plug). If it runs well and only has trouble at idle, and depending on what year your yukon xl is, it may just need a good throttle body cleaning.

10-07-2007, 08:55 PM
my yukon is 2003, already had the TB cleaned, that was recommended by the dealer. I still have the rough Idle at stops. My tach shows that that the idle is steady just at 500 rpm but I can feel the rough vibration in the steering wheel and pedals. Anyone every have this issue, if so please how did you fix it.

10-07-2007, 08:57 PM
can a bad gas filter be the cause of my problems?

10-07-2007, 09:08 PM
A plugged fuel filter generally causes more problems with acceleration. There is also a software calibration for the pcm to address throttle body issues on the 2003's. Do you know if the dealer updated the software? Here's the bulletin, and please note: this is NOT a recall, just a service bulletin to follow if a vehicle comes to the shop with this concern.

Subject:Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body) #04-06-04-040 - (06/14/2004) Models:2002-2003 Cadillac Escalade, Escalade EXT

2000-2003 Chevrolet Silverado, Suburban, Tahoe

2002-2003 Chevrolet Avalanche

2000-2003 GMC Sierra, Yukon, Yukon XL

2003 Hummer H2

with 4.8L, 5.3L or 6.0L V8 Engine (VINs V, T, Z, N, U - RPOs LR4, LM7, L59, LQ9, LQ4)

and Electronic Throttle Control

Condition (

Some owners may comment on an idle instability, low idle speed or rough idle.
Cause (

Condition may be caused by deposits in the throttle body bore.
Correction (

Clean throttle body bore and throttle valve plate of carbon using a shop rag and an appropriate cleaner. Refer to Engine Controls Repair Procedures - Throttle Body Cleaning Procedure. This procedure may be performed at any mileage necessary. Check to determine if the PCM calibration has been previously updated to one that includes the update for throttle body coking. For 2003 model year vehicles, look in the operating system portion of the calibration. For 2000-2002 model year vehicles, look in the engine portion of the calibration. If not, then update the PCM calibration to the latest calibration.

10-07-2007, 10:03 PM
Dealer said the recalibrated the PCM, but I don't know if they looked in the operating system. They just said the recalibrated and scanned the truck for codes.

09-15-2009, 10:20 PM
I had this same issue on a 2001 gmc serria z71. I was told the same thing from the dealership. they also told me it was a fuel pump. i replaced the pump still didn't fix my problem, so i took all the plugs out to changed them. but as i took them out i checked them for cracks, i found three plugs that where damaged.I replaced them and it solved everything. one of the plugs didnt have a visible crack but i held it but my ear a listened to the ceramic. i could hear what sounded like broken glass. I would check into your plugs before you spend to much money.

09-15-2009, 10:33 PM
I also cleaned to tb and cleaned as far into the upper plentum as i could, what i couldn't get to i just soaked with cleaner and let it dry before running the truck. it still smoked when i started it but it is normal after cleaning. it also wouldn't hurt to run some lucas injector cleaner, to clean out any trash that may have got into the system. this fixxed my problems and yours sounds just like what i was going threw, it is all simple to do. the plugs are the hardest part. took me maybe an hour to do

09-16-2009, 08:07 AM
Gentlemen please check the dates before posting, this is 2 years old, start new threads in that case, thanks.

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