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?? Any advice will be appreciated.

 

Update: Decided to start from scratch so... ACDelco cap rotor and plugs along with new wires. Pulled old plugs and to my surprise, the right bank plugs look normal with normal wear, but thte left bank plugs are all carbon rich. Any input will be appreciated. Thanks

 

if one side is rich than the only things I can think of is not enough spark, if it is getting to much fuel could be bad injectors for that side. but it seems it would make more senses to say that side has bad o2 sensor. maybe someone eles has some other ideas.

 

Hope we got this figured out, what do you think:
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 O2 sensors:
http://www.2carpros.com/forum/2002-c...ire+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.

 

Welcome to the forum.

The steady state miss does sound like a lean condition. Let us know how it turns out.

 

Thanks, It's really more of a random miss and why I'm apt to believe it's a detonation problem cause by the exhaust leak and the O2 sensor on the right bank.
Or...it could be 40 other things We'll see. Thanks for the replies, D.

 

Did you figure out the problem? My 2000 Chevy express van with the 5.7 is doing the exact same thing. The check engine light was on and the so I changed the o2. Sensor that was bad. The engine light went away but the truck runs the same.

 

Welcome to the forum.

Hopefully the OP got his fixed and will come back to help.

 

My 99 Tahoe is doing the same, and before I spend a whole lots $$$ need some answer to this, seem like everyone got the same......I was told it might be the fuel injection spider under intake......the cost for that part is over 500.00 and want to be sure before tackle that cause got to remove the top half of the motor to get to it. What do you think?
Mark

 

Mark
Your guess is as good as mine.....I'm not sure if its something that expensive I will do it.
M van has no lack of power and runs great except for these small hiccups.

Another thing with my van is right before I bought it a couple weeks ago it had spun its bearrings in the engine. The Guy I bought it from repaired it. Now the Guy who origionally posted this described it exactly lime mine.......I couldn't have described it better.

Could the hesitation have anything to do with the spun bearings..........

It seams to be common for these engines to spin the bearings.