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Computer problem

Discussion in 'EEC IV' started by CORanger, May 25, 2014.

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    1. CORanger

      CORanger New Member

      May 24, 2014
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      City, State:
      Bailey, CO
      Year, Model & Trim Level:
      1992 Ford Ranger

      My son bought a 1992 Ranger in March with a factory 4.0L, 3" body lift and 31" tires. When he bought it the seller said it had a lack of power. The PO had cut the cat off. After getting it home, we did the following work:

      Replace cat

      found it was running lean so I:
      checked vacuum and found it only had 8" of vac
      Did a compression test, all cyl between 130 & 140
      Computer data O2 sensor in open loop and about 100mv
      Replaced O2 sensor, data still in open and mv went to 30-40
      replaced intake gaskets
      cleaned intake
      vacuum came up to 12.5"
      computer data still showed lean
      replaced IAC thinking the vac was sucking the plunger open
      No change
      Replaced ECM
      Truck started running good, closed loop and O2 mv all over jumping rich and lean.


      He went to drive it to school and had the Left rear tire pass him because he didn't tighten the lugs all the way.

      Last weekend got it standing on all four tires again, truck ran great. Drove it about 50 miles, after we left a stop, going up a hill passing a car and it lost power again. Got it home and now it's running rich, O2 sensor in the 900mv. Checked FPR, no fuel coming nipple
      Checked fuel pressure, 32 KOER, but pressure would come up and drop the second the relay kicked out doing KOEO, checked bleed down after turning engine off, and it would drop stead and fast.
      Jumped the gun and figured an injector had gone bad and was leaking.
      Replaced the injectors and with the fuel rail on, turned pump on to check leaks, could hear the fuel and sounded like it was still leaking, no visual leaks, put intake back together and ran, same issue.
      Today pulled upper plenum, unplugged the injectors and ran a KOEO fuel pressure test, 38 psi and held.
      checked voltage to all connectors, 12v on all, checked resistance of all connectors to ground Left side open, right side near 0 ohms
      Disconnected battery
      Disconnected harness plug, rechecked resistance to neg battery cable open
      Reconnected harness disconnected from computer, rechecked resistance to neg battery cable open
      Tested resistance from computer pin 58 to connector near 0 Ohms
      Reconnected computer, rechecked resistance to neg battery cable near 0 Ohms
      Replaced new computer with old computer, still near 0 Ohms from connector to neg battery cable
      Now I'm stumped. Not sure if the new computer is bad or if something is telling it to close the ground in the computer.
      Someone told me it was a bad computer, but my concern is if I replace it with another new one, will it blow again?
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