1999 Chevy Tahoe 99 tahoe rough and high idle

1999 CHEVROLET TAHOE
11,100 MILES • V8 • 4WD • AUTOMATIC
Avatar
WHIP
  • MEMBER
  • 1 POST
I have a 99 tahoe with 111,000 miles on it. It was rough idling and so I changed the #5 spark plug and that fixed it for awhile. Then it started rough idling again so I changed all the spark plugs and it stopped for about three weeks. Now it high idles between 900-1500 and when put in gear with foot on the brake, car misses. I have changed the plug wires, added HEAT and fuel injector cleaner to no avail. The car runs fine at high rpm's. I have not adjusted the idle.
Jan 19, 2010 at 9:18 AM
Advertisement
Avatar
BRIAN 1
  • ✓ASE Certified Mechanic
  • 1,030 POSTS
  • ASE Certified Mechanic
check for a vacuum leak around the intake manifold gasket.very common.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. have the vehicle scanned for an codes also.start here first.
Jan 19, 2010 at 7:52 PM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.