Fuel injector?

My 88 VW Jetta just had the timing belt changed a couple months ago. Now, it’s started to hesitate when accelerating, idle rough, and burn lots of gas. I know there could be one or more of a few possible causes (like ignition timing or fuel injector), but where should I start with this?

Start with the cheapest,the spark plugs. If they have not been replaced that you know of or remember that would be a very good place to begin. The ignition wires can either be replaced now or along with the plugs. Let us know.

will do. Thanks.

OK, so I replaced the spark plugs and wires (the old plugs were a sight to see… “incredibly rich” as put by the guy at autozone) … I also put some injector cleaner in the gas tank… started her up, and she ran real rough for about 90 seconds, and stalled. Now I’m just thinking about replacing the fuel filter and the fuel pressure regulator in hopes that my troubles will be over then. Thoughts?

background info: timing belt blew about 3 months ago, was replaced at a shop, but the spark plugs weren’t changed since (until today)

Did you change the plugs and wires one at a time to make sure you hooked them up in the correct order? I would check to make sure they are hooked up correctly to make sure they are firing in the right order.

Is the air filter clean and relatively new? If not, that would explain why your engine is running rich. Check, and if necessary, replace your air filter.

You could KNOW if you need to change the fuel pressure regulator by measuring the fuel pressure. If the fuel pressure is too high, the engine will run rich.
The engine coolant temperature sensor can defect and cause the engine to run rich. This sensor can be checked, too, with a multimeter and thermometer. Repair manuals cover there kinds of sensor checks ---- either Haynes, Chilton’s.

I didn’t change the plugs/wires one-at-a-time. I replaced the distributor cap too. But, I’m pretty sure the engine wouldn’t have run as long as it did before stalling out if they weren’t installed correctly, no?
Air filter is a couple months old, still looks new.