Jetta Running Issues

[dumptruck]

Hello, i am needing some assistence in trying to diagnose what is wrong with a 94 Jetta. This thing has become a major thorn in my side and i am reaching out to try and find some answers. This is a 94 with 106k on it and it is a base model car with no power options at all, it is a 2.0 litre 4 cylinder gas version. The car has been well maintained and for whatever reasons developed a weird running condition. It seemed like a standard slight misfire and slight hesitation so i thought that it was a premature ignition failure since the car had received a full service at 60k. We replaced the plugs, plug wires, cap and rotor, with the proper Bosch parts along with the coil as these have been know to cause problems here recently. Now the car starts fine warm and runs ok but when you hold a constant throttle position the engine stumbles. When the car is cold you have to hod the gas on until it warms up or it dies, it will not hold idle when cold, once warm it will hold idle but still stumble on light accelaration and at constant throttle. So, i do not want to keep replacing parts that are not going to fix the problem so any help is very much appreciated.

[boschmann]

That type of engine management problem can be a real pain, especially since VW didn't do do-it-yourself nor independent mechanics any favors with their self diagnostic systems in those pre-OBDII ('96) days. Your car could have either two small connectors in the center console or the OBDII style connector beside the ashtray (which isn't OBDII compliant) for reading engine information, either way without the proper tools & information it will be tough.
I assume the check engine light isn't on and the ignition components you mentioned were put on more recently than at 60K, otherwise 46K on a set of plugs would need to be looked at first. If you want to check some things for youself, I'd start by checking for vacuum leaks at some of the lines and intake boot. In addition to physiacl inspection you can spray starting fluid around the intake manifold area and hoses and listen for idle changes. You can also check the temp sensor (located on the water outlet from the head to the radiator) with a multimeter. Resistance should be 2000-3000 Ohms cold changing to 200-300 Ohms hot. Also there is a flap in the air cleaner that lets exhaust warmed air in during engine warm up that could be malfunctioning, but thats not likely the problem. You can check for a fuel restriction in the fuel filter. Then it's on to fuel injection components that you really need some equipment to look at.