i have a 99 blazer 140k with bad misfire at idle.....but if the truck is in park and put the throttle at 2500rpm or above its like the mis is gone and it accelerates smooth but anything below that it misfires bad and once you put it in gear it doesnt want to stay running bc of the misfire. I was told it was spider injection so i got it replaced and after a couple days of cranking it and trying to get it started it finally ran but it ran the same way it did before the injection change. the plugs and wires have been replaced. also i read on here that the plug order on drivers side from the front is 3, 1, 5. well mine is set up 1, 3, 5. so i thought i found problem and switched them but once i did, the truck wouldnt start at all. a buddy thinks the truck might have skipped timing but i dont want to tear apart the front of the motor if i dont have to. If anyone has any ideas or has had same problem please let me know. im running out of ideas and need my only car back running lol. thanks

 

i have the same problem and i dont have a clue what it is. spider injectors are good and so are plugs and wires

 

You can check the timing by following the procedure in the link below:
EDI Engine Timing

Once you get the #1 piston to top dead center on the compression stroke and then align the two timing marks on the balancer as described, pull the distributor cap and see if the rotor is pointing at the '6' in the base.

 

you got a compression issue burnt valve most likly

there was also a tsb about lifters colapsing at idle also could be crank position sensor needs shimmed\recalibrated

 

I really hope its not a burnt valve bc that would suck to fix. Does anyone know about the whole spark plug thing? i read on this site that the order from front of car is 3, 1, 5 and thats what it says on the cap but the number 1 wire was on where number 3 is supposed to be and number 3 was on where number 1 was. I switched them and thought that was the problem but then it would even start at all.....so im not sure if some have different configurations or what. I guess the next thing to do is take the cap off clean it and check distributor timing and see where im at. If anyone has any other info that might help let me know. Thanks

 

The firing order is 1-6-5-4-3-2.

 

ah okay thanks. so the wires were on correctly. Hopefully i can figure this thing out. Whats weird is that last winter it had a misfire as well at idle (tho not as bad as it is now) and we couldnt figure it out. We took it to a shop and they said they couldnt figure it out (after charging us a bunch of money of course) so we just decided to drive it til it dies. Well somehow the misfire went away and it ran perfect until this winter and now the misfire is back. Could the weather be affecting something to cause this or is it just coincedince that it started misfiring in winter?