About 2 weeks ago I started having trouble at idle in gear. When I am running at speed it runs pretty much normal and runs great under wot, but at an idle under load it runs rough, kind of like one cylinder is not firing. It has a new distributor and I have checked that all the wires are connected, so I think the problem is fuel related. My car is 90% original with hardly any work ever having to be done on it. I have probably 80-90% original hoses, but I have looked for a crack or vacuum leak and don't see anything there. I am leaning towards a worn out tbi gasket, maybe intake gasket or just in a bad need of a tbi rebuild. I will say I couldn't tell you when (if ever) the fuel filter was replaced or fuel pump. Could it be either of those? Any advice? Anyone else ever had this problem? Any help would be appreciated.

 

Leaks in hoses are hard to see sometimes. It could also be internal in something like a vacuum storage "ball" or small pin hole in brake booster. Time and patients and you'll find it.