Why does my 1996 buick roadmaster have rough idling and missing?
I have a 1996 Buick Roadmaster 350 LT1 5.7, I am having some issues with the vehicle idling rough and seems to be missing. When I turn on the AC the car runs a little better and sometimes after shutting the AC OFF THE CAR SHUTS OFF.I went to AutoZone and had my car put on the computer and I got a EGR code P0400, Mass Air Flow code P0100, and a Catalyst code P0430. I replace the EGR, and mass air flow sensor, and my car is still doing the same thing. I was also told I may have a leaky water pump. I just recently installed new AC DELCO plugs and wires and a new air filter. Any ideas on what to try next or what could be my problem? NEW PARTS INSTALLED: PLUGS WIRES AIR FILTER EGR VALVE MASS AIR FLOW SENSOR See a video of my car running at https://www.youtube.com/watch?v=K028uIUMlpM&feature=youtu.be
Cars & Trucks - Buick - Roadmaster - 1996 Buick Roadmaster
Answers & Comments
I hate to be the bearer of bad tidings, BUT... it\'s obvious that these corrections you\'ve made [lots of $$$$$] have nothing to do with your problem.
Quite OFTEN idle and low speed engine performance problems are CAUSED by LEAKS in the VACUUM lines/system!!!!!
As a vehicle ages, summer heat, as well as engine heat, will cause the rubber or plastic of vacuum lines to deteriorate and either crack or become loose in their connection to nipples and tees in the vacuum system. This allows EXTRA AIR into the engine.
In the early stages of this process, the engine computer will be able to correct for the EXTRA AIR being sucked into the system.
However, as the air leakage increases with time and heat, the computer cannot fully correct, and thus engine performance suffers.
One fix is to replace all vacuum system components, BUT... that will COST HUNDREDS OF DOLLARS!!!!!
The way I have used to FIND vacuum leaks is to use a TINY PLUME of Propane from a small torch.
With the engine idling, gently open the Propane torch valve, "cracked" open just enough to be able to smell the Propane [DO NOT IGNITE/light the Propane, we only want a VERY small amount of gas, but NO FLAME!!!!!].
Then, apply the invisible tiny jet of Propane to EACH connection point in the vacuum system, while the engine is idling.
The engine idle speed [RPM] and sound should remain unchanged IF there is no leak at that connection.
HOWEVER, IF there IS a LEAK, the engine idle RPM and sound will change, and this is indicative of a leak at that point.
Once, when out of Propane, I substituted WD-40, and that worked also!
I suspect that any gas, either a combustible fuel gas, OR even a non-combustible gas would work because either would change the air [Oxygen] to vehicle fuel ratio, thus changing the idle RPM.
UPDATE!!!!!!
UPDATE!!!!!! After replacing the EGR and Mass Air Flow sensor I did not unplug the battery cable to reset the computer, so after doing that the check engine light went off for about 2 days and it came back on yesterday so I went to AutoZone and had it placed on the computer and the only code I got was the P04030 indicating that the Catalytic Converter is bad. I wonder is the code just a reference to a bigger problem or since it is the only code showing up ,is that my problem the actual CAT CONVERTER?Should I go ahead and replace it?