94 VW Jetta heat hiccup/hesitation

I have a 94 Jetta (manual, 200,000 miles). She has an intermittant problem in the summers. Started 7 years ago and has steadily gotten worse each summer. When it first started the outside temp had to be 90 or hotter, I had to have the air conditioner on, and I had to be in stop and go traffic for a while. When these conditions existed, she would hesitate and have slight lurching/hiccuping motions while I progressed through first and second gear. If I could get to third and get moving, it would work itself out. Now, the outside temperature only needs to be about 80, the air conditioner doesn’t need to be on, and I don’t necessarily need to be in stop-and-go to trigger it. Also, it sometimes now will start in third gear and stay constant, even when going 65 on the highway. She has never stalled, it’s just not comfortable to be jerking around. I’ve taken her to multiple mechanics over the years. She’s never displayed the symptoms, so they threw parts at her - CAM sensor, speed sensor, BG44K, etc. Nothing worked. She just spent a month with my mechanic, who got her to act up at times so he could run multiple tests. Only thing consistent was the intake air temperature, so he removed that hose. (Sensors were fine, fuel pump fine, etc.) When I picked her up, she acted up in 3rd gear and for about an hour on the highway. The only other thing was the idle sensor, which sometimes left a code, but my car has no problems when idling so my mechanic didn’t think that was it. Has anyone experienced similar symptoms with their jetta? If so, any advice?

Vacuum leak? I’d check that out to make sure something isn’t leaking vacuum, which will cause the engine to run rough. It could be a small hose, near the engine. The heat has slowly dried it out and caused it to leak more. It could be intermittent due to flex of the hose (cracks on one side).

If it is, replace the VW braided cloth over rubber hose with silicone vacuum hose and you won’t have to mess with it for a long time.

Thanks. I’ll mention it to the local mechanic when I take her in again and let you know how it turns out.

Well, symptoms got worse, to the point where she was almost stalling. Mechanic says oil is leaking into the air intake and only way to fix is to rebuild or replace the engine. Guess the oil leak is bad as oil is getting on my air filter. Didn’t make sense to pour that much money into my old car, even though I loved her, so time for something new.