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My 97, 4 X 2, 4.6 with 98K miles started backfiring. I suspected the camshaft sensor and replaced it. Still not fixed. I tried disconnecting the crankshaft sensor to see if it changed, would not fire / start. My next thought is to replace the Powertrain Control Module which has the integrated EEC. Could that be it. BTW the check engine light does not come on so I can not get any codes. Is it Possible that one of the timing chains has jumped and gotten the valve timing off?? Please help!! I really have doubts about the timing chain. I bought this new and have religiously kept the oil changed and have not abused this truck at all.
Some will post a code even without the CEL coming on. Go to your local parts store and have them scan for a code is you don't have a scanner. Now I know that this may sound a little far fetched, but it did happpen to aother car I had and a buddy had your same prob. Backfiring, running like crap....turned out to be crappy battery caused by a failing alternator. All seemed ok for starting, but output after starting was lousy. Electronic systems were not getting the right voltage and the puter was freaking out because of this. Not a common thing, but it can happen.
Never had a CEL come on. I did have a low battery due the fact this truck sits a good bit lately. The battery is one year old. I'll check it again it's been charging on a slow charger. The original Motorcraft Factory battery held out for NINE YEARS! The replacement does not seem to have the same will to live. I'll also check the alternater output to see if it is dragging the Battery down.
I had a scan done at the parts store and it read a P0102 VAC MAF low input. Also noticed there is no vacuum on the Brake Booster. I took the check valve off the vacuum line and no vacuum at all at any RPM, What next? I am trying to aviod the FORD Dealer $$$$. I think I'm loosing on that one. Any further sugesstions?