I've read the posts on code 41 and 91, and I have checked the vaccum lines for cracks, and have found none. (I do not have a vaccum pump) I just replaced both O2 sensors, and I am still getting the codes. Can someone explain to me where is the most likely place that a vaccum leak would occur. My gas mileage is crap, and I'm sure i have lost some power too. I took my a/c out,and the blower motor, but left the vac lines in tact. Could this be causing it? 
code 41 91
- Thread starter Shirley
- Start date
Finding vacuum leaks is a lot like going fishing. It requres some luck and some skill.
Use a vacuum gauge ($17 at most auto parts stores) to determine if a leak is present. You should see 16.5"-19" of vacuum at 650-725 RPM with a stock cam. More vacuum is better
Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent and no eyebrows is not cool...
Use a vacuum gauge ($17 at most auto parts stores) to determine if a leak is present. You should see 16.5"-19" of vacuum at 650-725 RPM with a stock cam. More vacuum is better
Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent and no eyebrows is not cool...
93 LX
Founding Member
check the PVC hose under the upper intake. Mine was bad, they are exposed to high heat and will get hard and crack
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