Ok so here's the story on my 98 Blazer LS. Traded my ATV to a guy for it, his son had overheated it and it wouldnt start. After it had sat a while the guy went out and started it up and coolant was leaking from the weep hole on the water pump. Replaced the water pump, thermostat, and dumped/cleaned radiator and coolant reservoir. Got it all put back together and running again and the engine was idling rough. It well rev all the way up and not have a problem but you do notice it when it is idling back down. At idle the engine is slightly shaky and you can really feel it when you put it into gear. Truck has 17xk on it now so I know its no gem but I wanna get it running before we get heavy snowfall. When we got it running I had the powrtuner for my grand prix and hooked it up and the CEL was for a misfire. Pulled all the wires from the distributor to see which was misfiring and found my culprit. Changed that plug and wire today and nothing changes. With all those miles a tune up is definatley in its future, So im wanting to rule out major issues before I spend the money on a tune-up and find out that money would be better used deeper in the engine. Besides a compression (and should i check all cylinders or the one that was missing) what else should/could i do to rule out the more expensive parts I would need? thanks in advance

 

since you have replaced the water pump have you checked the oil, transmission fluid and coolant? and yes will have to do a compression test on all the cylinders. are you still getting a misfire? what did the plugs look like?

 

I think you answered your own questions. I would do the comp check on all cylinders, but if it wasn't seized from overheating, it could have warped the heads, and possibly caused a coolant leak internally. Check the oil and make sure there is no coolant in it. If it's got that many miles and had set, it probably just needs some TLC.

 

cleaning the MAF sensor seems to help these motors out quite a bit too if its dirty enough

 

coolant doesnt seem to have lost anything, and still seems to be holding its color well. (not sure what id be looking for other than that)
I haven't yet drained the oil (didnt want to put a 30 dollar oil change in and have to swap out somthing big [hey, im a poor college kid lol]) but i guess that is probably what i will need to do.
The MAF should get cleaned out tonight.
The warped head is probably my biggest worry. My other concern was just a good way to check the injectors to see if maybe ive got one clogged up (my GP needs the fuel rail removed which requires moving all kinds of wiring around the supercharger, and they all come out at once not individually)
What should i be looking for in tranny fluid?
I will try to get a good look on the spark plug tonight
Anything else to be thought of?

 

bump in case I make it out to play with the vortec some tonight

 

been a while with no updates. what did you end up finding out?

 

Well, sent the heads off to have the valves looked at and they said that a few valves were definatley messed up in some way, So i will get those back friday and begin the rebuild. The gasket didnt look that bad so im really hoping that coolant was getting into the oil through either a head gasket leak I didnt see, or through another gasket somewhere. Once I get this issue with the timing chain cover figured out Ill be ready to start my rebuild and hopefully wont find an cracked block