94 Crown Vic Alternator Overvoltage + many codes


Sevensecondsuv

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So my parent's 94 Grand Marquis has been driving weird lately. It would randomly buck and jerk sometimes while driving. Yesterday it kept stalling but my mom was finally able to coax it home. I went out there today and it started up just fine, but started running rough after a few minutes.

I immediately suspected the fuel pump after yesterday's symptoms, but I decided to pull codes anyways. Here's what I got:

KOEO Hard Codes:
636 - Transmission Oil Temp

KOEO Soft Codes:
122 - TPS below minimum voltage
157 - MAF below minimum voltage
158 - MAF above maximum voltage
332 - EGR valve opening not detected
337 - EGR valve pressure transducer circuit above maximum voltage

KOER Code:
157 - MAF below minimum voltage

So I can now see why it wouldn't hardly run. But all those sensors were working perfectly a week ago, so instead of throwing new sensors at it, I'm looking for a common trend. What I see is alot of electronics going haywire all at once.

Checking the aftermarket Sunpro voltmeter I have installed revealed that the system voltage was about 16.2 volts at idle. I know it should be about 14 at idle so this seems high.

I then removed the alternator and had it tested at Autozone, which came back as a pass. But I still suspect the voltage regulator. Or perhaps the whole computer is throwing in the towel.

Anyone got any ideas? Should I order a new voltage regulator?
 


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martin

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I would pick up an alternater from the junk yard and throw that in. simpliest, easiest thing to do. Alternaters that are intermittant can be difficult to diagnose.
 

89DangerRanger

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Just because the alternator passed doesnt mean that its good, my ranger alternator was putin out over 200 amps and this was on a stock alternator. It literally ate my red top optima battery.
 

Sevensecondsuv

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I fixed this problem. A junkyard alternator fixed the over-voltage problem and a new MAF sensor fixed the rest.
 


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