Great site! I have a problem that just occured. I was idling at a light when the engine just started to run a little rough. It sounded like an exhaust leak so I went to my neighborhood exhaust shop and he said everything looks good, no leaks. I had a bad map sensor a while back that seemed to cause the same effect. I disconnected the wiring from the sensor but it’s still running rough and it seems to smell like it’s running rich. Any advice on what to check for. I’m out of work and just trying to make ends meet,keeping my costs down. Thank you to everyone.
The problem might be with a leaking fuel pressure regulator. If the regulator diaphram developes a leak, gas can be drawn into the engine via the vacuum hose. This can cause rough idling and you may smell gas.
The fuel pressure regulator is located on one of the fuel rails. It’s a small metal canister with a single vacuum hose attached. Locate the regulator, remove the vacuum hose, and if gas leaks out of this connection, the regulator is leaking and requires replacement.
Thank’s Tester, I pulled the vacuum line off of the fuel regulator, no signs of fuel. I started it up with the vacuum line off also. I attached a vacuum gauge to the manifold. It holds pretty steady at about 22". It drops to 0" and returns back after full throttle. I did a couple of tests I read in a manual. One on the air bypass valve. There’s no resistence between the connectors when it says it should be between 7-13. Another test was on the map sensor. Apply approx. 18" vacuum and it should hold, well it slowly went down. As i mentioned before with the previous map sensor, I disconnected the haeness and it ran fine. Are either one of these tests foolproof or do they act differently. Thanks
I had a similar issue in my 87 Taurus. It ended up being the distributor cap, which is a nice, cheap fix ($15?). Reserving the right to be wrong, I think you can look at the tab inside the distributor cap for discoloration. Tauruses of that era are notorious for ignition system problems. Good luck!
Since the fuel pressure regulator is apparently not leaking, you might consider pulling the spark plugs for an examination.
It’s possible that one of them could have simply up and died. This should be noticeable by reading the tips of the plugs.
I would agree with popping the distributor cap loose to make sure there is not any carbon tracking in there. (usually a faint line between 2 or more terminals and can be caused by a bad spark plug, plug wire, etc.)
Also agree with the possibility of an ignition module fault, which is pretty commn with TFI-IV cars. Either a weak spark caused by the module or a faulty SPOUT signal from the module, with the latter causing a seriously retarded timing issue. Any of this should show up as a sooty spark plug situation on all plugs, not just one.