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Misfires...

JimsZR2

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JimsZR2 Enthusiast

JimsZR2

Posted
Posted

Hey All. Got a 1999 Chevy S-10 ZR2 pickup with a history of misfires. I'm at 65,200 miles

 

It started again about two weeks ago with a PO305 misfire. I took it into the dealer

and they suggested a new distributor cap and rotor with the fuel service too. That was basically ramming 200 PSI into injectors, cleaning the throttle body, And fuel treatment. I just went outside to fire it up and yet another misfire after spending $500 last week to have all that stuff done.

 

I'm not sure what it could be as far as the problem. I know our Cat converters clog up, The Injectors clog up amognst other fine issues.

 

I called the dealer back and they said they would not charge me this time to find out whats the issue.

 

If anyone knows some insight and can guide me in the right direction it would be helpful.

 

Thanks!

 

-Jim

Haulin' 8.1 Enthusiast

Haulin' 8.1

Posted
Posted

If they did all that last week, this week try a new spark cable on cylinder #5 along with a fresh set of plugs. Ask them to verify the camshaft retard reading is still within specs. Bascially that's your distributor setting, like timing in the good old days.

 

Misfires can cause a clogged convertor but not the other way around.

 

Vernon

JimsZR2 Enthusiast

JimsZR2

Posted
  • Author
Posted
If they did all that last week, this week try a new spark cable on cylinder #5 along with a fresh set of plugs.  Ask them to verify the camshaft retard reading is still within specs.  Bascially that's your distributor setting, like timing in the good old days.

 

Misfires can cause a clogged convertor but not the other way around.

 

Vernon

 

 

 

 

Well, If it was the timing wouldnt the PCM retime it?

 

It does it every morning now. cranks about 5 seconds and it's really bad. but after it pops the SES light on the misfire goes away.

JimsZR2 Enthusiast

JimsZR2

Posted
  • Author
Posted

Well, i went and bought me a neat little diagnostic tool and the current code is PO300. Multiple/random misfire.

 

Any clue as to where to start replacing parts?

 

EDIT: Yesterday on my way to home Depot I got to about 30 MPH and the truck was misfiring. It was the longest time it misfired yet. ( around 10 minutes). While i was driving the SES light was flashing at me when I hit 30MPH. I turned around got back home and hooked up my Diagnostic tool. It shows the P0300 with a PD (pending code)

 

I took the coil off the truck yesterday and where the plug wire goes into it off the Distributor there was alot of corrosion in there. I cleaned it out really good and threw everything back together. I let it sit overnight so I'm about to get outside and start it up to see if it will still misfire.

JimsZR2 Enthusiast

JimsZR2

Posted
  • Author
Posted

Well, Started it up this morning to a misfire. This time it is a P0306 ( Cylinder 6 misfire)

 

It's at the dealer being diagnosed for free because they did'nt fix it last time. :jester:

Haulin' 8.1 Enthusiast

Haulin' 8.1

Posted
Posted

The PCM will adjust timing to compensate for distributor wear, however it can't realign the rotor and cap once it's worn beyond specs. So it could fire the spark at the right time and the cap and rotor are too far apart to jump sucessfully every time, or even to the right post, or even one post.

 

Have them check Camshaft retard, it needs to be within 3* of zero. When they leave my shop they are on zero even if I have to take the distributor bracket off and enlongate the bolt slot so it will line up. So far my customers love me. Usually they've been to the dealer a few times first same as you.

 

Vernon

  • 3 weeks later...
Shu Enthusiast

Shu

Posted
Posted
The PCM will adjust timing to compensate for distributor wear, however it can't realign the rotor and cap once it's worn beyond specs.  So it could fire the spark at the right time and the cap and rotor are too far apart to jump sucessfully every time, or even to the right post, or even one post.

 

Have them check Camshaft retard, it needs to be within 3* of zero.  When they leave my shop they are on zero even if I have to take the distributor bracket off and enlongate the bolt slot so it will line up.  So far my customers love me.  Usually they've been to the dealer a few times first same as you.

 

Vernon

 

 

 

 

 

On my old (1998) S-10, it did this too. Replaced the factory spark plug wires at about 50,000 miles and all was fine again.

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