Despite years of maintenance and upkeep, my Blazer started losing antifreeze last week and couldn't figure out where until I brought it into a shop. They did a pressure test and found out that the manifold for the intake cover valve was leaking a little (always knew about that typical Chevy defect) and the water pump was bad.

Given my schedule and where I live, I couldn't fix it myself, so I let them do it. And that's where it snowballed: when they put everything back together (even put in a new rotor and cap because it was going bad) the spider fuel injector wouldn't fire on two cylinders. Was told that it also was bad and fixing the manifold more or less likely put good pressure into the system, causing the fuel injector to go out. Reluctantly gave them the go ahead to replace it too because I wasn't about to tow the truck somewhere else.

And now the new problem: got truck fixed and it already idled a little rough. Was told that it was like that from new fuel system. Drove it over the weekend and it seemed okay, but then on Monday the "Check Engine Soon" light popped on. It's possible that it wasn't reset, but I have a feeling that something could be wrong with an oxygen sensor. Plan to take it into Auto Zone in the morning to see what code it gives, then plan to drive it back to the shop and give them a piece of my mind. Seriously doubt I can get problem fixed for nothing; probably be told that newer parts most likely caused older parts to start faltering.

Any idea what it could be and what to do?

 

If its a running rich code, its probably cause the new injectors are putting out more fuel than your old injectors and a sudden change like that may set a code, just a thought. Let us know what the code is when you get it scanned and that will narrow things down

 

I'll tell you a little story about "shops". I was heading home from VA in my Mom's Lincoln last Thanksgiving. The car started to overheat, I knew that a few miles ahead was a fimilar exit with a little auto shop I had seen several times making the trip.
So I got off there and pulled into his lot. Waited a little bit and he comes in and says "the thermostat needs changing, and the water pump is bad". I let him think I belived that as it I took it in. But... after I thought about it, I told the guy I was going to take it to the Napa across the street and change out the thermostat myself, and that I didn't trust him under the hood of that car. He said "Ok, You'll be back!" Bought the socket and extention, used the rachet in the trunk, a little blue seal, 50/50, and we made it home fine. That water pump was just fine! You can't trust a shop, unless you know them real well.. I hate to say it, but it sounds like you might have got "jipped" in there somewhere.
The money I payed for that socket, extention, thermostat, 50/50, and sealant, was probably more that what he would have changed the thermostat for. But I saved on the water pump and I know it was done right.

 

I would bet money that they bent one or more of the pins in the SCFI connector on top of the intake manifold and now are trying to get you to pay for their mistake. During the course of the lower intake manifold repair, they would have to disconnect this and it is somewhat easy (if you are working way too fast and/or just don't know any better) to bend the pins. There is no other connection between the two systems. The gasket they replaced has NOTHING to do with fuel supply what so ever and they would have had no reason to open up the upper plenum and otherwise mess with the spider. The only things they would have had to do would be to disconnect the electrical connection & remove the fuel line assembly that runs from the spider to the back of the motor. Neither of which would change the pressure (in a positive way) delivered to the fuel system or alter the injectors in any way other than the mentioned bent pins.

They messed up, plain and simple. Chances are they didn't properly install the distributor either. If they didn't take the time to ensure that the spider connection was lined up straight and proper before jamming it home, they likely wouldn't have taken the time to set the CMP Retard to zero after dropping the distributor in. And all on your dime...