need good advise from the best!

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badbird302

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I have a 93 mark with an unusal problem. when driving down the road i'm gettin an intermittent skip. no CEL or codes when checking data stream my Vref is 6.71v to 6.73v (seems high), but when I get the skip i'm losing Vref. all sensors drop out at that point, but the DPFE which stays solid at .57v, also intermittent is lack of comm. with scan tool. All grounds look good but it does have aftermarket batt. terminals. i'm thinking I may have a pcm problem but not sure how to test it with out unplugging everthing one at time, which wouldn't work anyway because its intermittent. any one with some insight on this symtom would be greaty welcomed, thany you in advance.
 
I know ya checked, but sounds like something is loose. Either the umbilical to main engine harness, ECU or power terminals.
 
umbilical? where is that? is it a ground? also it seems to be dropping with the same wave form every time, (looks like the reverse of a firing line
 
I know this is a PITA, but try un-plugging and re-pluggin in the connectors in the engine compartment - one at a time. We have seen after time, these connectors get high resistance from - whatever- and simply unplugging/reconnecting takes care of the problem.
 
badbird302 said:
umbilical? where is that? is it a ground? also it seems to be dropping with the same wave form every time, (looks like the reverse of a firing line
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Its the man engine connection, right by the brake booster. Like the ECU connection, an 8mm (I think) bolt secures it.
 
to add to the diag. I just noticed on data stream that MLPS is not reading park, all other ranges read normal and just checked adjustment, Its ok.
 
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