1999 Saab 9-3 turbo 2.0, Car has a rough idle and poor acceleration throwing code P0304, that is #4 misfire. I replaced spark plugs, DIC, and injectors, the problem still persists. cleaned the MAP sensor with electrical contact cleaner and it ran perfect for about 10 miles, then the problem started again. pulled the vaccum line with it running for a minute then put it back on and again it was smooth. but the problem comes back... so my question is: is this a bad MAP sensor, it does not come up on the codes and other mechanics say that if it was bad it would throw a code, so it must be something else... I think it is the MAP sensor just starting to go bed... what do you think?
Electrical contact cleaner is not good for map or maf sensors. There is a special cleaner for this however I have never actually had any luck with the cleaners. It very well could be the sensor going bad. Not being familiar with your car I can say I had the exact same issue with a 97 mercury cougar and it was the sensor. I would double check the plug making sure the gap is correct and it is not cracked, check the wire (swap to another cylinder if you can and see if the error code swaps as well), check the coil pack as well.
Hello
The engine
and automatic transmission in this vehicles drive train
are fully electronically controlled by a computer called the PCM
(Power Train Control Module). Whenever a problem like this occurs the
computer stores a record of the problem (there are of course some
exceptions to this, like the fuel pump, engine coolant temperature
sensor and MAF sensor for instance) in the form of a fault code in
its memory, to read these fault codes you must have the systems
memory scanned with a special tool. Once the fault code(s) are read
you then must perform the appropriate diagnostic testing to find and
resolve the problem(s) DO NOT REPLACE ANY PARTS UNTIL A
TRAINED TECHNICAIN HAS DIAGNOSED THE PROBLEM TO AVOID SPENDING YOUR
HARD EARNED MONEY ON PARTS THAT MAY NOT CORRECT THE PROBLEM
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