This is going to sound backwards, but hear me out.

Had a lot of problems with my 98 blazer 4x4 vortec. Did everything I could to fix it, plugs, wire, cap, rotor, fuel pump and filter. Still no running great. Finally died on me the other day. Finally decided that I've been beating around the bush and time to change injectors. I assumed that it still had the crappy sequential system in it, an decided that to save money, I'd just a reman of that same system. It's $100 cheaper than an MFI, and I just need to get it running so I can sell it and be rid of it.

So, I tear it all apart today, and low and behold, it's already got an MFI system in, not the sequential system. I think, well, ok. So I'm kind of going backwards, but whatever, I just need it running. I go to put the new spider into it and the poppet nozels are really loose in the holes, not tight like the MFI injectors were. They do snap and hold in, but you can wiggle them around quite a bit. It this normal, are they suppose to be loose like that. It's all still sealed under the manifold cover so it's not like it'd be sucking in dirty air, but it still worries me that they are so loose in the holes.

Any help would be appreciated.

 

heh.. that's okay. Now you got two different spiders to play with.
I cant see any reason to worry, You pulled a stock MFI, and the lower is likely production poppet.
Let us know how it turns out.

 

Do those two systems go in the same ports?

 

Yes, they both can be interchanged.

To clear up some misconceptions here. Both systems are sequential port fuel injection. The only difference is in the location of the electronic fuel injector. The SCFI (sequential central fuel injection) houses the electronic injectors in the body of the spider and the electronic injectors feed fuel down to pressure actuated poppet nozzles in the intake runner. The MFI (multiport fuel injection) moves the injectors down to the intake runner, eliminating the often problematic poppet nozzles.

I would not recommend purchasing a reman'd SCFI spider. The reason is that once the poppet nozzles get scored up from buildup, they will never really seat properly again. No amount of cleaning will correct this.

Now, maybe what we should be doing here is trying to help diagnose the actual problems which are yet to be defined in this post.