livinlo

Hello,

In the past few weeks I have noticed that my tahoe has a really rough idle. You can actually watch the tach noise dive when it is doing this, and it actually stalled on me the other day after making a short trip. Any ideas where to start looking for issues. O yeah about the same time I had the check engine light come on and it gave me the code of the gas cap. Replaced cap and reset computer.

Thanks
Brent

ZX1100F1

First check the fuel pressure regulator for a ruptured diaphram, these are inexpensive and take 5 minutes to replace.
Then clean fuel injectors, adding four 12oz bottles of Techron to a full tank of gas and drive till near empty will usually do the trick.

If still has problem then I would suspect a leaky intake manifold gasket.

livinlo

ZX1100F1,

Thanks for the information. I put 2 bottles of Techron in a full tank. I will check the fuel pressure regulator. I will let you know.

Thanks
Brent
Pittsburgh PA

03blackburb

Check your throttle body for carbon build up. You may need upper engine/intake cleaning.

ZX1100F1

I have never in my life seen carbon build-up on a throttle body.

73shark

I used to have to remove the throttle body on my 3.0L Mitsubishi V6 Dodge Caravan about every 12K mi to clean the carbon off it behind the throttle blade. Also had to remove the IAS motor and clean the carbon off the piston. Read somewhere that this is caused by reversion in the intake.

ZX1100F1

This is not normally an issue on a healthy modern GM V8 engines although you may get what amounts to a oily dirt build-up after several years of operation it normally will not manifest itself into a drivability concern so long as proper air filtration is in place.
There certainly is no harm in using the proper EFI intake cleaner on the throttle body, plenum and manifold though.

There are some engines that I understand have issues wit this but most are small and/or foreign and many are turbo or supercharged, carbon build-up on the back of the throttle blade is caused by exhaust gasses getting past the intake valve, this is a result of either a specific cam timing/phasing to that engine or can also be caused by worn intake valves/seats that no longer seal closed properly, if carbon build-up is a problem on the Vortec 5.3L engine then you have a mechanical malady that needs to be addressed.

livinlo

Ok I checked with my GM dealer they only will sell me a new regulator for $107.72. My local NAPA is $77.49 and Advanced Auto is $45.98. My question is should I spend the money and get the OEM?

Thanks
Brent

five20too

Hey everyone!!! I'm new to the forum and I wanted to ask about the regulator. Where is this located and how would I go about checking it? I have the same problem on my Tahoe that I just bought. It really starts to lug when the AC is turned on and it won't even let the AC work properly. Thanks for any replies.

viperjuice

well. looking at the engine from front of vehicle the regulator is on the right side of intake with a small vacuum line coming off of it, pull th eline off with car off and see if there's any fuel running out or if it's wet.. shouldn't be wet. if not, this isn't your problem. also, pressure regulator will give you a rouch idle, and extended crank only at first start, not usually while idling. throttle body build-up doesn't usually cause enigne to run rought, you can have a problem with engine stalling and rough idle due to build up if you recently reset the computer and disconnected th ebattery since over time the pcm learns the throttle position and air flow and adjusts, resetting all that with abttery disconnected. all of a sudden it doesn't know what to do. .. leaky intake gaskets, usually cause a rough idle at start up, before pcm uses ho2 sensor data to properly adjust air/fuel mixture.

does you truck idle rough at all times? cold, warm? does the engine actually shake a bit and has a misfire or does the idle just go up and down a bit? .. ..

FIVE20TOO -- if you have problems with the engine with a/c on, check the grounds on back of the intake/block. Pcm can sometimes draw ground through a/c system wiring due to having a bad ground and then when you turn the a/c on that ground goes away so it's lost all of a sudden. seen the wires brake right at the connectors..