What distributer?

[Maxxtraxx K5]

So I have had the hoe plugged into the tech 2, and the distributer was off -7 degrees, but only every so often.. Among trying to adjust it, it was set to 0, then it jumped to -17, then back to 0. So I'm thinking the bushings in the distributer are bad, so my question is at this point, what distributer should I look into for my truck? Thanks guys!

 

[blueflamed03]

ACDelco

it's worked for this long....

 

[SunlitComet]

STOP, What was the name of the data variable you were looking at?

---------- Post added at 11:52 AM ---------- Previous post was at 11:51 AM ----------

Just want to make sure it was cam retard and not advance timing.

 

[ezdaar]

My first thought on jumping timing is worn out timing chain or pickup coil going out..
Those pickup coils are notoriously bad about going doing stupid stuff on the way out..

 

[Maxxtraxx K5]

Cam retard yes. It only measures it once a key cycle. And it explains why the ping is intermittent I suppose, took it for a ride with the tech 2 plugged in, made it ping and watched the knock sensor, ( that was showing activity and a constant 4.9 volts) the egr, and that was fine. Not suspecting the distributer being off but it was reading like - 14 degrees. Or something like that.
Also its got 191 k on it. Lol so timing chain could also be adding to it I suppose?

 

[SunlitComet]

Uh, the cam retard should be a contsant data output item and on the '99's engine speed most be 2000 or higher when parked and checking it. In addition if it was off more than two degrees in either direction for any mechanical reason you would have logged a P1345 code. Have you actually tried moving the rotor to see if has problems yet?

Here is some info on the knock sensor if you like. It sounds like the 4.9v is just the supply sent to the sensor for power.

Operation A Vehicle Control Module (VCM) is used in conjunction with one knock sensor in order to control detonation. On a VCM application no KS module will be found as it is internal to the control module.

A 5 volt reference is applied to the knock sensor which has an internal resistance of about 100,000 ohms . This resistance will lower the applied voltage to about half or 2.5 volts . When a knock is present, a small AC voltage is produced by the knock sensor and transmitted to the control module riding on top of the already existing 2.5 volts . An AC voltage monitor inside the control module will detect the knock and trigger the control module to start retarding the spark incrementally.

 

[Maxxtraxx K5]

Hmm that's interesting about the knock sensor, cus it showed on the scanner in real time the voltage never changed when you could hear it ping, it showed activity, but no actual change in voltage.. So this means....? Lol when we tried adjusting the distributer, and cycled the key on and off we had it set right to zero 5 key cycles in a row. Tighted it down and the next key cycle was -12 on the distributer, not cam retard. Sorry for the mis info! Lol

 

[SunlitComet]

the 4.9vdc was the power being applied to operate the sensor so you know it has the proper voltage to operate. it always will show some activity which is output as a-c power detected by the computer it just show it as activity not a-c power detected. It is the knock retard and factor that your sensor is dictating to the computer to optimize the timing for best performance without pinging.

Perhaps I am not understanding you but what variable was -12 on the scanner. Did you mean actual real time advance?


Can I assume then when you were done moving the distributor and mounted it down that you measured real time Cam_Retard at 2000rpm or above when parked and it showed 0.0 degrees +- 2.0 degrees when you were finished?

Also what prompted this all to began with?

 

[Maxxtraxx K5]

Yes real time advance, and yes -1 at 2000 rpm in park. I talked to someone about the jumping in the timing, and they pointed to the distributer, either the bushings being loose, or the gear on the bottom being worn. That could be moving around causing it to retard it so much intermittenly, so the distributer is coming out this weekend so can see what if there are any issues with that. What started this whole thing was it would ping once in a while, and it has just gotten worse recently.

 

[SunlitComet]

I would try manually moving the the rotor back and forth to measure movement while pushed down and also how much it turn as it rides up on the gear. It would not hurt to start simple. I am sure you know that timing is not adjustable by the user becuase you claimed to adjusting in you original post. Is that correct?. If you had a constant For example -12 degrees retard and occasionally it changed it sound more like your computer was responding to pinging. Have you not tried a high octane gas to eliminate fuel property issues or looked at misfire history or for that matter other things that might contribute like a dirty egr system or clogging injector that could be leaning out your system?

---------- Post added at 06:12 PM ---------- Previous post was at 06:07 PM ----------