Thread: strange issue

The issue I'm dealing with is on my dd 98 gtp (high flow cat, magnaflow catback, poly upper mounts 180 t stat, and hai). Car has 173k and a new transmission. When in gear, stopped at idle, the car has what feels like a miss, but throws no codes and it clears up as soon as throttle is applied. In park the rpm rises to approx 900 and the tremble lightens but is still present. The rpm is steady as normal idle would be, but once in a while it'll drop when coasting at round 20-45, from 1200 down to bout 800-900, then come right back up. The stock boost meter also shows that it isn't making full boost until 4800 or higher (started after pcv was replaced). It has new plugs and wires, new pressure regulator, new pcv valve, changed sc oil, Mobil 1 oil. I'm curious as to what anyone might think the issue is. I'm back and forth between bbv, injector(s), or hand of god twisting my brain. Lemme know what you think or if you need any clarifying.

Sounds like a vacuum leak to me.

I couldn't find any apparent vacuum leaks, I soapy water tested some places to see the bubbles would deteriorate but nothin there. I also considered egr, but I pulled it and cleaned it and no change. I might go pull a few from the junk yard and see if there's a change.

try spraying carb cleaner or starting fluid around the engine to find any vac leaks, the idle will jump if you have one, most vac leaks suck in air, so i don't where the soapy water comes in, I've of heard people doing it but makes no sense to me. (haven't read of anyone ever finding one with soapy water here either)

I'll give it a shot and see if there's any reaction