I just bought the SMP MFI conversion kit for my 1999 GMC Jimmy after having a P0300 and a P0171 code. Reading on here it seems like this conversion is the best. It says that the gasket and the bracket are required but not included..my question: can I use the old bracket? or if I cant, is there any way to modify the old one for the new unit to fit? Answers would be appreciated!

 

I converted my '96 and got the bracket. It's about $25 or so and is worth it by not having to make one. I don't think everything would stay in place without it.

 

AC Delco and Delphi injector assemblies come with a new bracket and gasket. The bracket is what holds the metering body to the lower intake manifold. The old metering body housed the injectors, the new metering body does not, as a result, the body is designed differently and requires the new bracket. When installing the plenum, the assembly needs to be able to move slightly so it will self-align with the plenum. If it doesn't align correctly, it will leak vacuum.

 

so what you're saying is I have to buy a new one and cant modify the old one? im trying to paint a picture in my head of what I would have to modify on the old one.
for those who have converted, how is the hose routing? I hear you have to heat up the lines with a heat gun because they're really stiff? and as far as the cylinder numbers go, do you just match the number on the injector body to the number on the cylinder?

 

You need the new bracket. Match up the numbers on the housing with each cylinder. There are only two lines that you need to criss-cross. The lines will turn in the housing, a little stiff, but they do turn. Do not heat them.

 

so why would I need a new bracket when the new spider fits perfectly.....





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now I read the codes today before replacing and it went from a P0300 vanishing to a P0303 misfire on cyl 3....and a P0171 lean condition bank 1 is still there. So I replaced the spider and the misfiring on acceleration and easing up on the pedal (slowing down) is still there. what now? already replaced Dizzy cap/rotor, plugs, wires, coil....at a loss. but the old spider was leaking so it needed to be replaced anyways. any thoughts?

 

Either too much air or not enough fuel will cause a lean misfire. If it's a vacuum leak, it will be very close to the #3 cylinder. Start by checking the vacuum adapter in the plenum #3, and the vacuum lines #2 & #4 for leaks. Could even be the plenum gasket leaking.

 

this helps a lot! the hose going to the vacuum adapter cracked right off and I taped it, but the misfiring was happening before that. I will look for more leaks. would it be wrong to maybe consider a leaking head gasket or bad valve/valve spring?

 

Head gasket will not cause a lean misfire. Weak or broken intake valve spring, or a worn intake lobe on the cam could though, and it might not make noise! Look for the simple stuff first. If there aren't any vacuum leaks, I'd pursue the "not enough fuel" angle, possibly #3 injector is not squirting.


EDIT: One of the pins in the injector connector may have been damaged during dis assembly/assembly.

 

so head gasket is ruled out, makes sense because I don't have any coolant loss. now, I do notice a slight ticking noise at idle. could the lifters be the cause as well? to check for a bad valve/spring, should I go the compression test route instead of taking the valve cover off? I will look into those vacuum leaks and a bent pin on the injector connector.