Hi everyone,
​​​​​​I have a 02 Blazer and whenever the weather turns cold and rainy I get a misfire with no codes. It only happens on first startup of the day and if I pull over and turn off the ignition and start it right up it will run just fine. I put on a new ACDelco cap and rotor yesterday and although it runs a little better I'm still having this issue. It will kinda buck when I am at steady acceleration and let off the accelerator. Like I said, when I pull over and turn off the ignition and start it right up it goes away and runs fine for the rest of the day. Any ideas? Thanks

 

Put a small dab of dielectric grease on all the contacts in and out of the distributor cap. Possibly a moisture issue. Maybe next morning it is cold and rainy, take off cap and look for any condensation underneath.

It could be a expansion/contraction issue (exampl3: airspace in crank position sensor).

Are your plugs AC Delco?

Don't buy new parts until you do some trouble shooting.

 

Can your scanner read live data and graph?

George

 

Yes, plugs are AC Delco.

 

No, I just have a cheap code reader but I'm ordering a scanner today that can read live data. The code reader I have isn't pulling up any codes.

 

Let me know when you are set up and we can look at a few things to try and figure out what’s happening. Does the truck need to rest before the successful restart or do you literally just shut it off and immediately restart it to get trouble free operation?

Also, is there any history on the ignition switch?


George

 

No history on the ignition switch and no it doesn't need to rest, just turn off the ignition and after about 5-10 seconds turn it back on and it's fine for the rest of the day.

 

I have two initial thoughts about this. The process of turning off the truck and restarting it involves mechanically moving the ignition switch and it’s contacts and then restarting/resetting all of the sensors data like the TPS. Try wiggling the ignition switch the next time this happens while it’s still running. Also lighten the key ring as an experiment, one key only.

once you can read live data we can look to see if any sensor readings are goofy and get straightened out at the restart. We can also monitor system/ignition voltage.


George

 

Sounds good, thanks.

 

An additional thought. It’s possible that it could be fuel pressure as well. If you have a fuel pressure gauge you can monitor the pressure when it’s running bad and compare that to the pressure after a successful restart.

George