engine dies at low revs

Discussion in 'Workshop Forum' started by dan in new mexico, Jan 11, 2020.

  1. dan in new mexico

    dan in new mexico Daily Driver

    Location:
    silver city nm
    following replacing a bad battery and attaching new cable connectors...my x engine will die at low revs..i must keep revved to above 2000 to keep it from dying. previously would idle around a thousand. Could this be a few delivery problem..pump or whatever...or maybe even electrical? Insights appreciated. Thanks.
     
  2. Pete Whitstone

    Pete Whitstone True Classic

    Location:
    McKinney, TX
    Carb or FI? Either way, one cause of dying at low RPM is a vacuum leak. Check any vacuum caps and all hoses that connect to the intake manifold.

    Fuel delivery problems tend to have the engine cut out at higher RPMs, not limit its lower range. Electrical is very unlikely. except maybe in the high voltage stuff (dizzy cap, wires, spark plugs).

    Timing belt slipping is a remote possibility.

    What else changed with the battery and cable connectors? Did you remove and replace any other components? Or even just jostle them? How long since the car last idled well?
     
  3. dan in new mexico

    dan in new mexico Daily Driver

    Location:
    silver city nm
    sorry, fuel injection model 81. here's what happened. went to car wash...went to start when finished. would not start..battery quickly went down. it's possible water got on battery..shorted out..whatever..battery went bad...had to walk to walmart get a new battery hike back and install. did not really change connectors(almost new) just adjusted wires within the positive connector. three wires green to battery i presume,red and brown...would not start until the brown wire was making a good connection. so now it starts easily...but will not idle. was idling ok prior to the car wash and battery replacement...thanks for ideas..will check the vacuum items and electrical stuff..
     
  4. Pete Whitstone

    Pete Whitstone True Classic

    Location:
    McKinney, TX
    Car wash! Well there's your problem.

    I am betting that your drain hole on the passenger side under the engine cover is clogged and your spark module is or was under water. Take it out and dry it with a hair dryer.
     
    ecohen2 likes this.
  5. dan in new mexico

    dan in new mexico Daily Driver

    Location:
    silver city nm
    That was a wise idea pete...but...area seemed to be dry..unplugged and dried out anyway...but must be something else...plus...now i"ve made it worse..when your idea did not pan out...i thought well maybe i'll just tweek the co mixture screw on the air flow sensor a bit to see if that might regulate the idle. slot was at about 11'clock posistion so i moved the slot to 12...did nothing to improve idle...so moved it back to orginal posistion....now the engine will not start at all..wiser heads..please advise if i did something stupid. Strangely...when this happened i swapped out the air flow sensor with an identical unit from another x...then even with a different afs with untouched co mixture screw...engine reacted the same...run for a second or two but not really turn over and keep running. So at this point i would be happy to go back to easy start..but keeping it revved up! could tampering with the co mixture caused such a result?
     
  6. Pete Whitstone

    Pete Whitstone True Classic

    Location:
    McKinney, TX
    At this point I'd go back to basics to try to isolate the problem area. An engine needs 3 things to run:

    1. Compression - run a cranking compression test. This will point out a slipped timing belt, among other things. Make sure you have good compression across all 4 cylinders.

    2. Spark - Take a plug out and make sure it is getting a good spark on cranking. If so, then throw a timing light on it and make sure the spark is occurring near TDC.

    3. Fuel - substitute a squirt of starting fluid past the doggie door and see if it roars to life. If so then you've got a fuel delivery problem.

    Those basic diagnostic tests should point out a road to go down.
     
    kmead likes this.
  7. dan in new mexico

    dan in new mexico Daily Driver

    Location:
    silver city nm
    sounds like a plan..i'll get on it...thanks.
     

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