OK, heres the dealio. 1992 GXE with 140K and all regular maintenance kept up. Few things along the way have been replaced within the last 6 months such as coolant temp sendor, O2 sensor, plugs, wires, cap and rotor all new injectors with new connectors, fuel filter and air filter. After replacing injectors car still has slight chugging at idle (made more notable by my leaking flex pipe) but runs well, almost perfectly if you overlook the slight rough idle. I replaced a few sections of vacuum hose recently. Correct me if I am wrong, I am assuming the idle condition oh, it's also a little fast at idle (about 1,000 RPM) is likely caused by a vacuum leak. What are your opinions for the best way to rule out or locate vacuum leaks? I've hear spraying carb cleaner etc around and watching for a change to engine speed, just want some ideas of whats worked best for all of you and confirmation I am looking along the right lines. I really want my max to run like it was new.. if its not vacuum I guess all I have left to replace is the knock sensor, throttle position sensor and clean the idle air control valve.. if I forgot anything please let me know :-)

 

Here is a general outline for solving your problem...

1) Buy MAF cleaner, TB cleaner, and starting fluid...Clean the TB, IACV, MAF, etc with the appropriate cleaner.
2) recheck / replace plugs, wires, PCV, cap, rotor, etc.
3) check TPS
4) there are a lot of vacuum lines...remove the intake plenum and all of the vacuum lines will become apparent...replace any / all of them that look worn.
5) if your idle has a rhythmic misfire, it is an injector, which are known to be problematic...I didn't have any problems until last month...now I have had 2 go out in 3 weeks...it can happen

If you suspect injectors, PM 4thgradeddropout...he has a whole set of new injectors for cheap...good luck!

 

best way to find a vacuum leak is with a small propane tank and a hose.
you open the tank a little and use the hose around potential points of leakage if the rpm goes up you found the leak.
Carb cleaner works similarly, but isn't as pinpoint accurate as the propane.

 

If you don't have a propane tank and hose, a small bottle (like you use for a camp stove or lantern) and a propane torch head will do the trick. Don't light the torch, just open the valve a bit, and do the same test with it. If RPM's go up, you've found a leak.