Do I Have An Intake Air Leak?
Posted 08 April 2007 - 06:02 PM
After the truck is warm it idles almost perfectly. Occasionally, I will see a momentary drop in RPM from the tach and can feel a little roughness in the idle.
Mileage is 103,500
Does anyone have any links that shows how to replace the intake gaskets? I have read it only takes about 2, 2.5hrs to complete the job. I have replaced the fuel injection in my '96 Vortech pickup. It doesn't look like this would be any harder. Does the whole intake come off or just an upper section?
Posted 09 April 2007 - 12:17 AM
Posted 09 April 2007 - 12:09 PM
Subject: Cold Engine Idle Misfire Or DTCs P0171 P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake leak lean misfire miss P0171 P0174 P0300 power rough surge vacuum
Models: 2002-2005 Cadillac Escalade
1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer
1999-2005 GMC Savana, Sierra, Yukon
2003-2005 Hummer H2
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
99 through 05 GEN III truck engines may experience any of the following:
A cold rough idle that diminishes as the engine warms up.
Possible DTCS P0171, P0174, or P0300.
Random misfires at idle.
The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.
If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.
The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
Posted 09 April 2007 - 01:44 PM
Posted 09 April 2007 - 02:03 PM
1 of 447 | 12.7@109
Posted 09 April 2007 - 05:52 PM
hmm well like i said taking the intake off isnt that hard of a job.. could be done in a hour or so.. good luck on finding the problem.. wonder if you could spray some intake cleaner around the intake to see where it is leaking??
do you have a picture of what it looks like? Do you have to drain the coolant for this kind of job?
Posted 09 April 2007 - 08:03 PM
Posted 09 April 2007 - 08:27 PM
4 Bolts come out of the fuel rail and then 5 or 6 on each side of the intake.. You are going to need a quick disconnect tool to undo the fuel line coming in..
The open holes are of course where the injectors go... you can see where the fuel rail bolts up too.. there is also a couple of hoses you have to undo.. make sure when you reseat the injectors to lube the o-ring with diletic grease..
This pic shows where the coolant runs through the throttle body.. might have a little bit come out.. those hoses are a booger to get off.. while youve got it apart would be a good time to get the fittings and do the throttle body bypass...
Edited by ridnlow, 09 April 2007 - 08:28 PM.
Posted 09 April 2007 - 10:23 PM
Posted 10 April 2007 - 06:53 AM
Also the engine ran smoother than normal for some reason when I tried it yesterday. It seems to only be a problem when the temperature falls below 45-50 degrees F. I am wondering if something else is going on that may not be an intake leak.
I just bought this Tahoe about 2 months ago and I am not sure the last time the fuel filter, plugs, etc has been changed out. It has 103K miles and I am sure the injectors could use a cleaning.
How would I get into the TB to clean it? Mine is a 2003 and it uses a motor to open and close the throttle plate. There is no cable attached to the throttle. I don't want to damage something.
ridnlow You mentioned something about a throttle body bypass. What is that exactly?
Posted 10 April 2007 - 10:31 AM
The throttle body bypass is where you hook the two hoses that run coolant through the throttle body together, thus bypassing it.. its pretty much a free mod.. you can really feel it on a cold day..
Posted 10 April 2007 - 05:20 PM
Posted 12 April 2007 - 05:20 AM
Nevermind, I just found the spec from another thread!
Edited by USSBURB, 12 April 2007 - 05:25 AM.