GJJ

I own a 1989 VW Jetta GL (4 Dr) Sedan. It has a FI 1.8 Gas single OHC engine. A 5 speed manual trans. I've owned it since new. I have enjoyed owning this car. I had garaged it during the winter mo.s for the first five years that I owned it (Nov-Apr). It has 55,000 miles on it. About four years ago it started running poorly, on cold start. Hesitation, stumbling and stalling until nearly warmed up. During the warm weather, with A/C on and a quick pull off throttle and pushing the clutch in to make a quick slow up or stop, motor drops off and under load from A/C compressor engine stalls. After sometime, I started going over a few things (dealership not much help except for suggested troubleshooting, potentially adding up serious diagnostic costs before possible big dollar repair). Three weeks after I bought the car the Digifant II control unit just died. It was replaced and the car ran fine until the afore mention four years ago. I started with and replaced distributor cap rotor, plugs, wires. All with high end or Bosch parts. Recently I replaced the oxygen sensor (Bosch), and did an Ohm test on the Airflow sensor (Airflow sensor within Ohm spec.s). A brief summary of how it currently runs would be, in the morning first start of the day (engine good and cold) I let it runn a few minutes, temp gauge off of cold. Then start driving. Then its like you unplug a house fan wait a few seconds and plug it back in. I just loose power and it comes back on again. This occurs until engine nearly but not fully warmed up. Then after fully warmed up it runs like new. I installed a block engine heater a few years ago when I started using the car during winter mo.s. When the car is plugged in overnight it runs much better no stalling, unless defrost is on and quick stop (compressor load) engine stalls.

Any suggestions would be greatly appreciated.

Thank You!

boschmann

First, I'd check the coolant temp sensor, it's the blue plug at the head where the upper radiator hose exits. Resistance should be 2000-3000 Ohms @ 68F (higher if colder) and 225-275 Ohms @ 195F (operating temp). If that's okay I'd check fuel pressure since it only requires a simple gauge. The test port is on the left (of car) side of the fuel injector rail w/a 7mm plug in the end. Pressure should be 35-40 psi running & should increase about 5 psi when you disconnect the fuel pressure regulator vacuum hose. It should also hold at least 25 psi for 10 minutes after shutting down. Also you can try clamping off the 1" hose from the air intake boot to the idle air valve when it is cold. It should die. Once the engine is warm when you clamp off the hose it should only affect the idle slightly, but not die.

Evolver

I have a Jetta 86 CIS-E 1.8 8v and had exactly the same problem after I changed some parts, I went to a mechanic who knows of VW and told me that after I changed the Oxygen Sensor the gasoline mixture (excuse me my english, im latin-american) went bad, so he fixed it and the car ran like new.

Hope It helps.