Okay I am running out of ideas here. What could cause an engine to miss and stumble terribly only when its not up to temp? At high or full throttle it runs fine. Once up to temp, everything is cool. HELP!

 

Could be moisture in the ignition system causing spark to scatter. Once the truck warms up, it dissipates the moisture due to the heat.

One thing that I have seen cause this sort of thing is blocked drains in the distributor. Some distributors have screens in the bottom that are supposed to filter out dirt/debris, but end up getting clogged and allow moisture to collect in the distributor.

 

I have the same problem as clauglin89 and I just put in a new distributor and the miss is still there???


HELP!!..........MORNING MISS.......Driving me nuts!!

99' Blazer 4X4 full size 4.3
Has anyone figured out the problem that causes the MORMING MISS?
I've had it in the shop for a total tune up, fuel pump pressure test, changed the distributor out and it's still there. Just in the morning till the engine warms a little, than it will run like new for the rest of the day; no matter how long it sits after inital warm up, you can't get it to miss??? NO code. other than random missfire??

PS. The miss only happens with inital start up in the morning when I take off at normal speeds. But, if I take off like a dragster, with the peddle to the metal, it does not miss, Go figure!! This morning miss started @ about 125000 miles.

 

Have you cleaned the EGR valve? Your problem may be there.

 

I have the exact same problem with my 2000 blazer! its drivin me nuts! only in the moring before the engine warms up. ive replaced the distributer cap, rotor, plug wires, and plugs and its still there. i havent checked the egr yet so that is my next step but still are there any other things that could be causing it?

 

If any of you find out what is causing this problem, please don't forget to post it. The missing doesn't last long enough to find out what is causing the problem. I've had it in two reputable shop's and they couldn't find it either..........THANK'S

 

I've got the same issue in my 97 bravada...only in the morning it seems, I asked my older bro who's an army mechanic what he thought and he suggested maybe the fuel filter could be gunked up, which would explain why it only happens when the truck sits for a while

 

if i remember correctly my buddys 95 blazer just like mine had that issue and i replaced his engine temp sensor in the driverside head..problem solved

 

the coolant temp sensor?

 

ok so i took off mt EGR and gave it a good cleaning. . . still nuthin. then i unplugged my MAP sensor and it ran fine jus a littlt harder when shifting. so should i get a new MAP sensor or should i look at the distributer.