Hello all, i am troubleshooting a rough idle on a 99 blazer.

After going through all the normal quick checks for the cause of the rough idle i decided to check the distributor play, it had some up and down play and some play in the button rotation.

How can i tell what is normal and what is to much play??

I hooked up a scan tool and at idle it goes anywhere from 15 degrees to 21 degrees, seems like its junping around causing an uneven idle!

 

If you are reading timing, that has absolutely nothing to do with the distributor other than the spark passes through it. Timing is determined by the PCM based on input from the crank sensor. Nothing you can do to adjust it other than reprogram the PCM.

CMP Retard (Cam sensor Retard) is the thing that can be off due to a worn distributor gear. I measured my rotor movement at the tip of the rotor with a dial indicator some time back (for someone else), and with a new Skip White distributor it is around 0.025" back and forth. No real discernable up/down movement. CMP retard need to be 0.0 +/- 2.0 degrees if you want to avoid misfires from the rotor pointing to the wrong position inside the cap.

 

I read somewhere that from the factory the cmp was +6, mine is +7 and with a Tech 2 I have absolutely no misfires.... I am still going to look at adjusting when it warms up outside.

 

I have always seen CMP to be 0°±2°; perhaps you can relocate where you read the +6°.

I suggest to loosen the distributor clamp bolt, connect Tech 2, start engine, let warm and then with a gloved hand try to twist the distributor while monitoring CMP. Distributor is not going to move much as it is not supposed to...but you may see CMP change 1 or 2 degrees toward 0°.
Since you have a Tech 2; take a look at the crank sensor, heck remove it and clean it off, re-install it, do a relearn using your Tech 2 and see what CMP goes to.

Lastly if the distributor is OEM, suggest replacing it as the plastic housing with brass bushings just do not seem to last. The Skip White aluminum housing replacement distributor is only around $50. I have had no problems with it and has been there for over two years now.

Good luck.

 

I would caution the OP hbryant123 to not disturb the crankshaft sensor in any way unless he has a way to do the crank sensor relearn procedure.

 

You may need to oval out the hold down clamp hole to get to zero. Things wear on theses truck knocking them out of being set right. I bought a new skip white and had to oval the hole on it. Very happy with the skip White, Quality made

 

Lesmyer: I was under the impression that the Tech 2 details out the crank sensor relearn procedure which is why I suggested it. That is my story and I am sticking to it....LOL......

 

Yes LannyL81 you are correct with info for me and I have a tech 2... and thanks for your info , Lesmyer was directing his response to hbryant123 and I dont think he has a tech 2.

 

yep, just didn't want the original poster to try it without the ability to relearn the crank sensor!!

 

Well CRAP!...I sure got my postings mixed-up! That is what I get for putting postings up in the wee morning hours when I can't sleep and apparently do not proof read very well either.....CRAP!...CRAP!......CRAP!....

I will try to do better in my replies.....