Hey all My name is Anthony. Im From BC and I just picked up a 1995 GMC Sierra.

high KMs somewhere round 269,000? ---- Ive had trucks with more lol

Anyways I have a few things ive been trying to trouble shoot with it.
rest assured I have used the search and found some help but I need more specifics.

The truck runs rough while idling in park. If you rev the motor it does have some hesitation then smoothens out at higher RPMS.

So... Today I tore into it a little bit to have a better understanding of whats going on?.... and this is what I found..

Cylinder #1 spark plug has an ugly oil coating.... fouled?

I removed the plug and exchanged it with another good plug I had laying around here to see if it may just be a dead plug.... but no spark.....

I changed the plug lead to the distributor Keeping the new plug just so i knew it would be all systems go... but still no spark..

keeping in mind all 7 other plugs had typical normal deposites and good spark...

any ideas as to why just the #1 plug lead has no spark? could this be timeing? and if so... would this not effect spark on the other plugs?

I did also remove the coil lead and turn the motor over while the #1 plug was out and can see the piston moving normally....


Any ideas, tips or suggestions would be greatly appreciated

Thank you all in advance for any help.

 

Pull the distributor cap off and check the contacts, my guess is that the contact to #1 is bad, missing or damaged in some way. Timing will affect all the plugs.

 

Ok thanks for the info I just wanted a second opinion before I did go ahead and start peeling it apart further....

were expecting rain for the next day or so... so Ill have to go and take it off today...
my thoughts if it where to be a dirty corroded contact would be to use alcohol...? to clean it.. any thoughts against this method?
eitherway I will tear it apart.. updates to come.

 

You could try and clean it if it is dirty or corroded. You might be better off just replacing it.

 

*update*

Ive Removed the distributor cap & rotor. ALL contacts where very corroded. For now Ive cleaned all the posts & the rotor.

put it allback together and boom she fired up and the #1 plug has spark.
since the cylinder has been running with no spark it was puffing blue-ish smoke out the exhaust. un-burnt fuel & oil im assuming...ive seen similar cases before. just burning off.

however the check engine light is still comming on.
soill have to do some more troubleshooting with that later...
off to go buy new plug leads, plugs rotor & dist cap.

FML lol

 

Took a couple pics while I was at it...
waters only in there couse it started to shower.

 

My suggestion is a complete tuneup. All new plugs, wires, cap, rotor, oil change. The truck should run MUCH better. Is it a TBI engine? You might consider pulling off the TBI and rebuilding/cleaning it. With that many miles, things can get gummed up in there.

I don't know how mechanical you are, but if you're in the mood to give your new truck some love, I'd pull the distributor (Mark it's relationship to the motor at the base), replace the ICM and pickup coil. This is not completely necessary, but really wouldn't hurt anything.