Hi everyone. im actually asking this for my girlfriends 99 blazer 4.3. it is throwing a code for #3 cylinder misfire and at idle is running pretty rough. once the throttle is above idle it actually runs decently smooth but it has no power (obviously bc its running on 5 cylinders). she has taken it to a shop and then to the dealership and has spent well over $1000 for them to figure out this problem just for them to tell her they have no idea. they scanned the computer and installed new plugs, wires, checked fuel pressure, checked coils and they say every sensor is working fine. im just wondering if anyone else has had this problem and could possibly know what it is. im wondering if maybe theres a broken spring? or burnt valve??? any suggestions would be very helpful. Thank you

 

The #3 injector could be bad. When they check the fuel pressure, it's for the whole system, not just individual cylinders. Check your compression. That would be the easiest way to determine if you have a bad valve or what not. Do that first. Have the cap and rotor been replaced? If not, you will want to do that as well. After that, you might want to consider buying a new poppet nozzle for that cylinder and see if that helps.

If none of that fixes it, it MIGHT be that the distributor has gotten bad, but I am pretty sure that it would affect more than just the one cylinder. It could also be something mechanical, like a bent lifter, flat cam lobe, etc. that is preventing the correct A/F mix to enter the cylinder.

 

okay i will definately check those things but i wanted to know if anyone could help narrow the problem down. the code was for #3 cylinder misfire and the SES light was on but today i was driving it and now the light is off but the misfire is still there. is this normal? im really thinking it is the spider injector. my sisters husband told me that on the 4.3 vortech the spider injector is a common problem bc the lines crack and leak. Does this sound like the most probable answer? ive never worked on this engine before so i could use some help. i read a couple forums on here that said you can take something off and check for leaks before completely removing it. Can someone tell me how to do that?? also any other suggestions would be helpful.

 

That is a common problem. It wouldn't hurt to change it out. Worst thing that will happen is you are out $60 for that one injector.

The light went off because the SES light only trips if it detects a misfire that is too far out of spec for the PCM. I have a misfire in my blazer and the light only comes on if I take it on the freeway or get the RPMs up in park. During idle and city driving, it's too little of a misfire to set the light off and set a code.

As for taking something off and checking for leaks, the only way that I know of it to remove the upper plenum, which from there you can inspect the whole injector assembly, as well as remove them.

 

okay cool. i heard that you couldnt just replace the one injector that u had to replace the whole spider injector assembly but that would be awesome if i didnt have to. also could it still be an injector when the misfire is bad at idle? it misses pretty bad at idle but once ur on the gas its pretty smooth. i can still feel a misfire but not nearly as bad as when its at idle.

 

if your planning on replacing all the injectors i'd do the conversion to MFI from the SCPI. I think that is about the best thing to do instead of messing with the poppet's. i think you can just change one at a time but you'll probably end up with another bad one soon if it is the injectors. from my past experiences when you fix one you might as well fix all of them. the conversion you can get from autozone for 300$ and that is for the whole set up with injectors and all

 

i agree. That's what I did. But if you're low on cash, getting the single poppet injector will hold you off until you can get enough money to buy the whole thing.

 

I'm having the same problem..but my is the 4cyc and I change the inj,spark plugs,wires, cap and rotor...I put a new cap and rotor and it was good for a week and its back so I did a new cap and rotor and it was good for a day....but I'm in the boat as u...and don't know what to do

 

before you do anything i would do a compression check on all cylinders if #3 is way lower than the rest you either have a burnt valve bad head gasket or possibley cracked head but thats pretty rare if compression check is good then i would look at fuel injectors