A very long story shortened to a few sentences and to hopefully help those with a random miss, horrible idle after engine warms up issue.

Bought my 2001 ZR2 Blazer in January.

New intake gaskets installed, new valve job, head gaskets, timing chain and cover, new distributor, cap, rotor, wires, plugs, fuel injection spider system, O2 sensors, MAF sensor, MAP sensor, IAT sensor, ......ALL PARTS AC DELCO.

Constantly had a horrible idle after warm up, sluggish performance, no power etc......codes were p0101 and p0102 which are MAF sensor related. Hence the NEW O2 sensors, Temp coolant sensor, MAF, MAP etc (I eventually wanted to replace all those anyway as this is going to be a complete restoration project back to like new condition). Still ran like crap after replacement of new parts.
Was thinking I need a camshaft position/crankshaft position sensor re-learn since they were both new. Was also thinking by coincidence that the cat was bad.......was ready to take it to the shop for a complete diagnostics.....

Engine finally threw a check engine light as it was under load going up hill (stuttering) and that turned into a p0303 code, which is #3 cylinder miss fire.

Pulled the NEW plug out and everything looked normal......BUT.......after looking very closely, I noticed a very small hairline crack in the porcelain, replaced with a new plug and WOW...Engine runs like new!

What I think happened is that the small crack was not significant enough to miss fire (ground out) at cooler temperatures, but after the engine hits the 195 degree operating temp, the heat caused it to expand enough to cause all kinds of havoc!

I hope this helps those who have the same issues with theirs.

 

good news congrats. I chased the same issue once and it was a loose plug. After trying everything i decided to check the plugs one more time. I was tight enough when cold but after everything warm up and expanded it was loose. Sometimes its so easy but we over look it

 

Thanks for posting about your solution. These types of posts are super helpful!

 

Christine it would be nice to have more people post solutions to issues they have resolved, whether they posted and asked for help or not. I can't tell you how many hours/days I have spent on automotive forums with my detective hat on piecing all the "what ifs" together for what seems like a "Check this first" type issues.

Anyway, your vacuum hose post a while back pointed me in the right direction to replace all my vacuum lines, what a big help.

 

I feel the same way about follow-up posts. But you know I can see how once a person gets their rig going again that they are so happy they forget to send back a final report. Hence my appreciation with people who do do that.

As for my vacuum line post, thanks for letting me know it was helpful. I figure when I do posts like that (or follow up posts) it is a way of "paying-it-forward" for those whose posts in the past were super helpful to me.

Speaking of vacuum: I got a new replacement vacuum solenoid valve for my HVAC control system. I suspect it is leaking. When I get the old one out, I'm thinking it might be useful to post pictures of my disassembly of it to see if it is repairable. Perhaps it can save someone some money.

 

funny you should mention that, I'm hearing a small vacuum hiss coming from behind the dash, although everything works properly I have a feeling its a leak. When I turn the system to off, it goes away.