Distributor installation and timing set instructions needed

I have the SUV listed above with a misfire on number five which is probably an injector. But, I wanted to replace the distributor cap and rotor with an upgraded one. In doing so, I found out that the plastic distributor was broken on the mounting screws for the cap. I purchased an all aluminum distributor online which is a direct replacement and much better than the factory plastic one. My problem is that since I installed it, I have noticed my gas mileage has gotten worse. The sticker under the hood says it does not have to be timed. Is this correct? How about if the distributor is off a tooth, will this matter? I have put plenty of distributors in my older cars that I have to time with a light. This one, just seems a little weird to me. What is the correct procedure to install? Thanks

Thanks for responding right away! I am a retired GM Tech, I have been away from the newer engines for awhile. I do not know too much about the newer systems OBD II. I am pretty much old school. Anyway, I was just concerned because I pointed the distributor rotor to face forward before removing. When I installed the new one, it was slightly to the left(passenger side). I thought maybe this would matter, but when I read up on it they say it does not matter. This truck does have a misfire, intermittently under load mostly. I fear it is an injector but wanted to cover the simple stuff first. I do not lose coolant, the wires and plugs are good. I just want to make sure this truck is safe for long road trips. I bought it used a few months ago. I replaced mostly all the things that go wrong with the truck. IE: Gas tank unit and pump, etc. How about cruise control problems? It does not work. Someone else told me they had problems with the multi function lever. Is this true?

Thanks again for the response. I checked over everything today. I am currently getting really poor gas mileage since I switched the distributor. I checked all connections and vacuum lines. I even sprayed some carburetor cleaner around the intake area to see if the idle increased. No! It looks like the upper intake was removed before. The bolts show some scuff marks on them. Plus, the wire looms are not installed correctly. I have a cheap scan tool for OBD II. I will do as you requested on the O2 sensor reading while it misfires. Today, it misfired so severely that I could only do 30 mph until it cleared out. Check engine light came on PO300 and misfire code for number five again. I did have great mileage before distributor replacement even with the misfire. I was going to check for TDC today but the balancer does not have a timing mark so I will have to take out number one plug and do it that way and recheck the placement of the rotor. I still fear it is a tooth off. Will this matter if its off a tooth? I am about ready to purchase a full service manual for this truck. I have many older manuals from GM, but none with this type of engine. Thanks again!

I am doing a complete engine swap on a 1999 Chevrolet Tahoe with a 5.7 Vortec engine. I bought a GM replacement crate motor. I have both motors side by side on engine stands and before I removed any of the major parts I removed the valve covers on both motors and rotated both of them to match each other at TDC top dead center. I made sure the valves were all in the same sequence on both motors. I then marked the Rotor and distributor and it so happens to be just past the number one cylinder not by much. I figured it was running and in time when I removed it and if I match that I should have no problem with the new one. I installed the distributor today and lined up all my marks. Not knowing electronics on these vehicles I just wanted to double check to see if there was anything special I needed to know about installing the distributor. Well I found many instructions stating and showing how to install the distributor lining up the white paint marks on the housing and the dimple on the shaft. Then when it is installed the rotor should be lined up with the notch or arrow with an 8 stamped in it. What I do not understand is the first part of the instructions about finding TDC top dead center is what I did. If I follow the instructions and the rotor is lined up with arrow or notch with the stamped 8 that puts the rotor between number two and number four on the cap no were near number one or my marks. If I follow my marks just like I pulled it out of the old motor it puts the rotor right on number one. Not knowing how the electronics work this is confusing me. Do I stick with my marks witch lines TDC with number one cylinder or do I follow the instructions? Please help me clear up this confusion. Thank you

I cannot see the injectors. They are under the plastic upper intake. This is a "R" engine. Throttle body on top with the spider injector system contained under the plenum.

I did not remove the distributor cap, and marked the shaft and removed the distributor. When I replaced it I adjusted the distributor by rotating the cap instead of the correct way. Now I ca not start the car. Please help

I also have a 1999 Tahoe with a 5.7. I have a cylinder 5 misfire happening and I’ve replaced the plugs, wires, distributor, ignition coil.

When I install the distributor after setting it to compression stroke TDC on cylinder one - line up notches and drop the distributor, it seems to me you can’t even be a tooth off because it seems it only fully seats in one position ( could potentially be 180 off, haven’t even tried because it’s pretty obvious the general position it needs to be)

Anyways, in order to line the metal conductor for the first cylinder on the cap with the rotor - I have to rotate the cap onto the valve covers and it just doesn’t seem like the right position.

I went ahead and installed it and when I started it up, it ran really smoothly and the check engine light stayed off, it wasn’t until I drove it when the check engine light came back on and started running rough again.

I turned the motor to get it to top dead center with the distributor out. Could I have messed the alignment up? Any insights would be appreciated.