Working on my neighbor's 01 suburban 1500, 2wd, 5.3, 90,000ish.

It's been having a hard time starting randomly, especially after sitting for awhile.

I first checked plugs and wires and they were OLD so replaced them. Problem still exists though.

Since then I've replaced the fuel filter (Wix) and checked the following:

1. Fuel pump primes properly (~3sec after switching on)
2. Fuel primed pressure = 45psi
3. Fuel pressure at idle = 48psi
4. Fuel pressure max while revving = 51psi
5. Fuel pressure drains off to 10psi in about 30 seconds after shutoff.
6. Removing vacuum from fuel pressure regulator during idle raises pressure to 60psi.
7. Vacuum nipple on regulator DOES NOT have fuel in it or seem wet from fuel.
8. Fuel pump volume seems normal (anyone know the spec on this)

Anyway, I'm thinking it has a faulty regulator. I'm a Ford truck and Honda car guy so not alot of experience with GM products. Any help is appreciated!

 

might try an injector cleaning or several bottles of techron thru a couple of tanks of gas.... if you are going to go as far as to pull the intake for the regulator might consider doing the injectors and poppets as they are all in the same place...

 

The regulator is on the driver's side fuel rail and takes all of 10 seconds to remove with my hands......don't know why you say remove the manifold??

I will try injector cleaner but I'll stick to Lucas brand, the only one I trust.

 

my bad your on the 5.3 and I was was thinking the 5.7 on the older body style...
if you have had success with Lucas then by all means... I only suggest the Techron well for one its the one I trust and have had success with, and I believe it is GM approved...

 

Also give this a once over....

Document ID: 1527156
#04-06-04-040: Idle Instability, Low or Rough Idle with
Electronic Throttle Control (Clean Throttle Body) - (Jun 14,
2004)
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.
Warranty Information
For vehicles repaired under warranty, use:
Subject: Idle Instability, Low or Rough Idle with Electronic Throttle Control
(Clean Throttle Body)
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
Labor Operation Description Labor Time
J5480 Throttle Body - Clean and Adjust 0.2 hr
Add: To Reprogram PCM 0.4 hr
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a
vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and
safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that
condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT
VOLUNTARY
TECHNICIAN
CERTIFICATION
© 2008 General Motors Corporation. All rights reserved.

 

Are you an Alldata subscriber?

 

Hey shark not sure who you were directing the question to
I am a subscriber to alldata however the particular TSB listed came from

http://ww2.justanswer.com/uploads/Bl...e_cleaning.pdf

if that was your question...

 

Just curious. Didn't know about any other sources for TSBs. Tried that site for another question and they wanted $s.

 

Huh... I just Googled the TSB number "04-06-04-040" and it was the first pdf that came up...

 

I asked a medical question about tinnitus.

Where'd you get the TSB no.?