2000 Chevy Tahoe Running rough

Tiny
UNCLE D
  • MEMBER
  • 2000 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 135,000 MILES
I have a 5.7L/ 350 vortec in a 2000 Tahoe, that is kept tuned-up. I started to notice an occasional miss at speed. Then this developed into a rough idle also. My OBD II scanner read "multiple cly. Missfire" The distributor cap had the inside center contact nub for the coil damaged. Replaced cap and rotor. Still same symptoms.
Also noticed that during acceleration, there is no misfire, only at steady speeds and at deceleration. At one time the distributor was replaced and all fuel injectors and regulator under the intake cover.
Should I start with a fresh tune-up and go from there?
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Thursday, June 24th, 2010 AT 9:32 AM

4 Replies

Tiny
BMRFIXIT
  • EXPERT
If have the flat distributor cap (wires goes on the side )
have many problems and I would have it checked and if at fault replace with the best quality available
inspect and suspect the coil
use a spray bottle fill with water and a bit of soap spray lightly the wire and coil as engine running (try it in a shady dark area if possible )
look if arcing in between the wires cap and coil

Use a test light
ground it and run it over the ignition system (wires, cap, coil )looking for spark arcing out the system and if so replace as needed and repeat the test

check fuel pressure
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Thursday, June 24th, 2010 AT 7:31 PM
Tiny
UNCLE D
  • MEMBER
Checked fuel pressure and volumne, all checked out. Pulled plugs: left bank, all plugs burning rich. Right bank, all plugs normal wear.

Replacing cap and rotor and plugs with AC Delco. Replacing wires with BWD Select
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Thursday, June 24th, 2010 AT 9:04 PM
Tiny
BMRFIXIT
  • EXPERT
No codes?
No vacuum leaks?
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Thursday, June 24th, 2010 AT 9:10 PM
Tiny
UNCLE D
  • MEMBER
BMRFIXIT, I meant to thank you for the replies, so thanks.

The only code is "random cyl. misfire".I've been told fuel, coil/ignition control mod., and Mass air flow sensor will not show a specific code. Others have said that is usually a fuel problem and it could still be, but why only is the problem showing on the left bank. I'll start with the tune-up because I want to isolate what the problem is, so then I'll look at sensors and control modules, then if all else fails a new injector spider kit.
Anyone that has any ideas, please chime in. I hate throwing parts at a problem, but I'm stuck. Thanks, D.

BTW, what type of test light for the Ignition system

Just thought of a possible fix: I found a small exhaust leak at the collector flange (I have shorty headers)so I have ordered collector gaskets. After reading this post, the second or third commit about O2sensors:
http://www.2carpros.com/forum/2002-chevy-tahoe-2002-tahoe-egr-valve-vt442666.html?highlight=cylinders+misfire+runs+rough

I'm wondering if I actually have a lean/detonation problem on the right bank(due to leak before the O2 sensor) and not really a rich condition on the left bank. Maybe not a misfire but really a detonation problem. Also noticed that during acceleration, there is no misfire, only at steady speeds and at deceleration. So would that mean during acceleration, it goes to a rich condition therefor no miss/detonation, and miss/detonation returns at steady speeds and deceleration because it leans out again.
Anyway, I will defiantly repair the exhaust leak, do the tune-up and go from there. Thanks, D.
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Friday, June 25th, 2010 AT 8:48 AM

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