Sorry, it's a V-6 question but I'm pretty lost on these... I've been asked to patch up a 92 Century with the 3.3L EFI. The idle is really rough, no vacuum to the brakes but it runs fine at higher RPM. uzzled: Some mechanic just changed the alternator, plugs, and wires with no success (the better half's friend took it in and got fleeced) and now I'm being asked to take a shot before the car is scrapped. My first guess is complete computer failure (no engine codes are being thrown), second is MAF sensor failure, thrid guess is timing...last... vacuum leak...o No: Help... o No:
My first guess is vacuum leak. The fact that it runs rough and you have no vacuum point that out. Vacuum leaks can be either really easy or really !@#$ to find. Let the engine warm up and idle it, then spray carb + choke cleaner in little spurts around the intake gaskets,fuel injector o-rings, and vacuum hoses. If you have a leak, the motor should rev up a little when the leak sucks the carb cleaner in. Be sure to check for leaks around the EVAP canister and the canister purge solonoid also. Good Luck.
Take a look at the PCV valve and grommet - may have worked its way loose or have a cracked grommet. My cousin had an early 90's Bonneville with the 3.8 V6. The PCV actually blew out of the grommet!!:af: Wouldn't run below about 2500-3000rpm, but above that it at least ran. Definitely sounds like some kind of vacuum related issue. One other thing - make sure the EGR valve is working correctly! That might cause a poor idle too.
Thanks guys, I sure appreciate it! I checked the injectors, fuel pressure, and ECU last night.. no luck. I'll go after the EGR, PCV, and do a smoke test for leaks before moving onto the vacuum leaks at the :af: gaskets...
