SirNike80

I have a 1999 Chevy Suburban w/ a 5.7L Vortec engine. It began misfiring on idle and it has continued, throughout my driving. I changed the distributor rotor and cap, spark plug wires, and I am still having this misfiring. The code is P0375. Even with me clearing the code, the misfire starts up about 5 mins after clearing the code.

Any help would be appreciate it.
Thank you

in2pro

Welcome to the forum

An intake manifold that has a vacuum leak may cause a misfire.

Inspect for the following:

• Improperly installed or damaged vacuum hoses

• Faulty or improperly installed lower intake manifold and/or gaskets

• Cracked or damaged lower intake manifold

• Improperly installed MAP sensor

The sealing grommet of the MAP sensor should not be torn or damaged

• Improperly installed throttle body or damaged gasket

• Warped intake manifold

• Warped or damaged cylinder head sealing surface

in2pro

Are you sure about the code? all the listings I find come up as

"P0375 Timing Reference High Resolution Signal B Malfunction"

"P0305 Code - Cylinder #5 Misfire"

in2pro

Service Information 1999 Chevrolet Chevy Suburban - 2WD | Escalade, Pickup (Classic), Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1861549
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#06-06-04-046: Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or P0430 - (Sep 12, 2006)


Subject: Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or P0430


Models: 1999-2007 Cadillac, Chevrolet, GMC Full-Size Pickup and/or Utility Trucks

with 4.8L, 5.3L, 5.7L, 6.0L or 6.2L VORTEC GEN III, GEN IV, V-8 Engine (VINs V, C, 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™ and E85 Flex Fuel




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If you encounter vehicles that exhibit the above conditions, refer to SI for the appropriate DTC(s) set. If no trouble is found, the cause may be due to an ECM ground terminal that has corroded with rust over time. Inspect the main engine wiring harness ground terminal (G103) for this condition.

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.

Engine Wiring Harness Ground Terminal Location (2007 Full-Size Pickup and/or Utility Trucks)




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




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).
Remove all rust from the ground terminal, the cylinder head and the retaining nut or bolt.
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).

Apply some type of electrical moisture sealant to protect the harness terminal from further corrosion.

EdherJAlvarado

I have a 99 Tahoe 5.7 and had the same problem, I actually had a few misfires, (#3, #5, #6)replaced all sparkplugs, cables, rotor, cap, still same. Then replaced the fuel injector system, still the same. It end up being the cylinder heads. I bought both rebuilt from a friend and now my truck is running like new.

Flyen81

I have a 96 Tahoe 5.7 Vortec I had just filled up my fuel tank went to leave gas station it started shaking really bad I put it on a scanner and it came up cylinder#5 misfire it ran great before that what can I do to fix it

frank0936

In the illustration that is included 3 posts up, can anyone tell me where the picture for the 99-06 ground is located? The posts keep saying on the right cylinder head, but I don't have any cables connected to the right cylinder head. That would be the passenger side head. I think the OP meant the left cylinder head (driver's side), but I don't see anything that I can identify as that part in the picture.
Thanks,
Frank