98 S10 4.3 Blazer. My baby. Has 200k miles and ticking.
Couple months ago was cruising along. Suddenly check engine light comes on, as I came to a stop at a light I could feel it idling rough, to the point of shaking. Later that evening when I got it home, the light had gone off, the shaking had stopped. Back to purring like a kitten. I didn't think much of it but gave her a very minor tune-up anyway. New air filter, changed oil, check wires, all looked okay. Three months pass. Yesterday, same thing happens. CEL comes on and rough idle at stops. Almost feels like its missing but not quite. What could come and go like that, causing CEL to come on and simultaneously causing shake?

 

You need to find what code it is throwing. I'd bet it is a misfire. I'd suggest besides the code reader, put some injector cleaner to start.

 

Hey fellas
Autozone plugged up the scanner and it came back with the following:

Cylinder misfire detected- cylinder # 6
explanation: the power train control module monitors the crankshaft and has detected a misfire
probable cause:
1- ignition system fault - sprak plugs, ignition wires, coil
2- vacuum leak
3- injector fault
4- high or low fuel pressure

I'm rock bottom poor and can't even afford spark plugs, let alone take it to a mechanic.. i know sad right... so this is my plan, steer me right.

remove wires and plugs (i saw the tech tutorial on the #3 plug, i know its a bitch)
check wires for any breaks, splits, etc.
clean plugs with wire brush, check gap
check air filter
check for cracks in cap
replace everything, see if it helped

2 years ago i replaced fuel filter so don't think its that

if i have to sell my leg to buy a set of wires, are auto zone brand wires OK? (Duralast)

Steer me to the egr valve so i can remove and clean that too, please. and many many thanks for all your help and guidance.

cheers, thomis

 

I'm following the steps to get started on removing the plugs and wires when I find this... and I wonder if this could be a vacuum leak? And I don't even know what the line goes to:

 

Those vac lines need to be fixed however they are very unlikely to cause a single cylinder misfire. They could cause lean codes or random misfire. You need to be looking at the ignition system first. Spark plugs, wires, cap and rotor. Second the fuel injector. These engines are not known for vac leaks that cause misfires

 

I removed the number 6 spark plug per the code. Does it look bad? I checked the gap to be 0.065, pretty close to specs. The wires looked fine to me, I mean I'm obviously no pro but they weren't cracked or worn looking. I looked at the wire going to plug 6 and it felt like it had a good seal and came off fairly easily with a gentle twist. I think the plugs and wires are 4 years old. I probably put 30k miles in 4 years.

I attached pics of the plugs. I found a plug in with some misc car parts I have (see pic). Is there any reason why this plug wouldn't work in the Blazer? Or should I try and clean the one I took out, regap, and put back in?

Also, I removed the cover at the end of the drive shaft (I'm going to remove it to replace the #3 plug). I may have broke this plastic cover (see pic), I can't get it to snap back together.

 

pic of cover/ boot

 

Wires can go bad internally and look fine on the outside. Swap #6 wire a different cylinder see if the code follows the wire. You can not just use any old plug it must be correct for the application. The plugs you had in it are junk. I am surprised they worked at all. Bosch plugs should only be in European cars but for some reason chain stores push them. They must make the most profit off them. Regapping and cleaning could work but it is the wrong thing. When plugs are worn out they should not be re gapped they should be replaced. Move #6 plug to a different cylinder (other then where you move wire) See if it follows the plug. REPLACE which ever one it follows.