QuestionI have replaced a map sensor,plugs,wires,air filter,vacuum hoses etc. looks good. Uncertain to what can be wrong and cant seem to get a reading. My husband bought a handheld diagnostic tool which gave him the map sensor reading. But the car still doesn't start every time,only on occasion and can not be run long before it dies again as you're driving it.What else could be the problem?
AnswerHi April,
It may be there is a component that is on the edge of failure but not enough to pass the threshold for a code. I assume that he did get a code, but can you tell me the 4-digit number of the code? And did he try to disconnect the battery, then reconnect, which erases prior codes in order to see what new codes come up after driving/starting it for a while? It will always set a 1684 code when he does that but ignore, it is just saying that the power to the contol module was disconnected recently, and that too will go away on its own. But anything other than that code would be of interest.
There is one component that can malfunction but not be noticed by the control and yet cause hard starting and dieing when coming to a stop: the egr valve. This exhaust gas recirculation valve needs to be fully closed when starting and when slowing down or the engine won't start or it will die. Here is how I have described this to others:
"The first thing I would do is check the mechanical function of the egr valve which is located along a pipe that runs from the left exhaust manifold (on the side of the engine facing the front of the car) to the intake manifold area (where the incoming air in the large rubber tube enters the throttle). That valve is metal and has a round fitting with a vacuum hose attached, mounted on the top of the valve, and the round part is attached to the main body of the valve by a sort of saddle. Inside the open saddle you will see a metal rod (with a slot) that connects the round top fitting to to the valve body. That rod is a stem on the valve and it is supposed to go in and out in response to the engine vacuum which varies with RPM and throttle opening (gas pedal position). Take a spray can of WD-40 or other penetrating lubricant and spray the stem where it enters the valve body and then use a regular screwdriver blade tip inserted in the slot to lever the valve in and out to try and free up its motion. Also check all the rubber vacuum hoses associated with the valve and a nearby vacuum solenoid valve. If the valve seems to open (against the action of a spring) and close firmly by the spring action when using the screwdriver blade to facilitate the motion, then you should be able to now start the engine. You can, once it is idling, check that the valve stem moves when you rev the engine from idle to 2500 rpm and back to idle. If it still won't start, then removing and cleaning the interior of the valve, or buying a new one if it seems too crudy and corroded inside, is the next step to getting the engine to start."
So give those ideas a try and let me know how it works out, please.
Roland
