Mechanics

CHEVY ROUGH IDLE AND ENGINE MISSING

2004 Chevrolet Trailblazer

2004 Chevy Trailblazer 6 cyl Four Wheel Drive Automatic 88,000 miles

hi, I am a one-owner of a 2004 trailblazer 6 cylinder. I have been having a problem with missing and rough idle. The problem has been gradual and getting worse. The service engine light stays on and intermittingly flashes when the miss is really bad. I have had a tune up. Coils, plugs, converter change, fuel pump and filter, secondary air pump, and camshaft sensor all changed. The secondary air pump was filled with water when he changed it. During a diagnostic run I had over 500 misfires in cylinder 3 and over 60 in cylinder 4. I am at my wits end. No one has been able to know what my problem is and how to fix it. I have spent literally thousands and feel like it is driving worse everyday. Could this be egr or any ideas?
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Rdouglas
May 10, 2008.




Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

Tiny
Rasmataz
May 10, 2008.
Check the crankshaft sensor, its the one that detects missfires.

Merlin2021
May 10, 2008.
I just bought a 04 trailblazer and it has 106000+ miles on it and it has a rough idle the code read p0302 missfire number 2 cylinder I took it to the shop and he told me that this engine was inherant for intake gasket leaking and that he had just fixed one with the same problem I tried to put new plugs and coil boots on all coils and I switched the number two coil to a different spot to rule out the coil and now it reads p0300 random missfire detected i'm going to have the gasket checked for leaks you might try it as well good luck with it !
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Tiny
Nthomas
Oct 3, 2009.
Where is the crankshaft positioning sensor?

Tiny
Cpaton
Oct 24, 2009.


http://www.2carpros.com/forum/automotive_pictures/62217_trail_1.jpg


Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P030...
Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or P0430 TECHNICAL SERVICE BULLETIN Reference Number(s): 06-06-04-046, Date of Issue: September 12, 2006 1999-2007 Cadillac, Chevrolet, GMC Full-Size Pickup and/or Utility Trucks; with Affected 4.8L, 5.3L, 5.7L, 6.0L or 6.2L VORTEC GEN III, GEN IV, V-8 Engine (VINs V, C, Model(s): T, Z, B, 3, M, 0, J, R, U, N, Y, K, 8 - RPOs LR4, LY2, LM7, L59, L33, LC9, LH6, LMG, LY5, L31, LQ4, LQ9, L76, LY6, L92); with Active Fuel Management(tm) and E85 Flex Fuel Related Ref Number(s): 06-06-04-046
ARTICLE BEGINNING
SERVICE INFORMATION
The wire terminal (G103) attaches either to the front or to the rear of the right side cylinder head, depending on the model year of the Full Size Pickup and/or Utility Trucks. If the ECM ground terminal has been found to be corroded, then follow the service procedure outlined in this bulletin to correct the corrosion issue.
Fig. 1: Engine Wiring Harness Ground Terminal Location (2007 Full-Size Pickup and/or Utility Trucks)

Fig. 2: Engine Wiring Harness Ground Terminal Location (1999-2006 Full Size Pickup and/or Utility Trucks)

1. Remove either the nut or bolt securing the main engine wiring harness ground terminal (G103) to the right cylinder head. Refer to the above illustration to determine where the ground is located on the vehicle (1). 2. Remove all rust from the ground terminal, the cylinder head and the retaining nut or bolt. 3. Position the main engine wiring harness ground terminal and install the nut or bolt.
Tighten:: Tighten the retaining nut or bolt to 16 N.m (12 lb ft).
4. Apply some type of electrical moisture sealant to protect the harness terminal from further corrosion.

Merlin2021
Oct 24, 2009.

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