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Vacuum hoses in a mess

OldcarsRuleOldcarsRule MontanaPosts: 3
edited February 2019 in Pontiac
I was having a hard time getting the car to idle properly. I took the carb off too see if fuel was getting to the engine without interruption, while the car was idling. The car backfired through the intake manifold and lit the engine compartment of fire!! After I put the fire out I re coated all the burned wiring, but I need help knowing where the vacuum lines go, and possibly what was causing my initial problem.

Comments

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    There should be a vacuum diagram affixed to the underside of your car's hood.

    Also check on the Autozone website. They have quite a few vacuum diagrams posted online.

  • OldcarsRuleOldcarsRule MontanaPosts: 3
    You were right, Auto zone has the diagram, do you have any idea why it wouldn't idle properly before I melted stuff? It felt like it was running too rich when it idled and starving for fuel when it was driving.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Rough idle and stalling can be so many things. Vacuum leaks are certainly one suspect, but there's tune-up problems, carb problems---you always start at the basics and start at the Simple and move to the complex. Do you know how to extract trouble codes from the OBD-1 system? I think you can get that info on YouTube. You really need some kind of data or you'll be working blind and guessing---and guessing is expensive.

  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 24,246
    The poster doesn't give the mileage on the car or any history.

    I'd suspect rotting or cracked vacuum tubing might have been a problem--that's been replaced now since the accident.

    But I'd want to do a compression test to see how the engine is balanced in its firing. Ring wear with the earlier oils may be a factor especially if the owners weren't punctual with their 3000 mile oil changes before the days of synthetic blends and now synthetics. The valves may also need grinding to improve the seats and sealing.

    A good garage with the old fashioned oscilloscope and a quality technician call look at the voltage patterns and diagnose to lot of problems, as @thecardoc3 here has shown.

    Although it's likely down the list, I'd be sure to go back to basic AC Delco spark plugs and wiring such as were standard equipment on the original vehicle. Years reading and posting in forums on H-body GM cars convinced me switching brands and using the nonstandard spark plugs along with different spark plug wires can give symptoms. I recall a friend who bought an Oldsmobile midsize wagon in the late 80s. It never ran right. Eventually he found it had 2 spark plugs that were correct and 4 that were not the right plug for that V6 engine. That really helped calm down the engine problems he had.

    Good luck getting this back in shape!. Just my opinion but these engines were walking a tortured line between giving power and meeting EPA regulations of the era without the control of fuel injection controlled by computers we have now.

    2014 Malibu 2LT, 2008 Cobalt 2LT, 2015 Cruze 2LT,

  • OldcarsRuleOldcarsRule MontanaPosts: 3
    I had previously rebuilt the engine ( rings, bearings, seals, head, made sure valves were seated, ect.) so I was thinking that it might have something to do with the fuel delivery/ air ratio so maybe some sensor? Does anyone know where I could find vacuum lines? The originals were hard and I cant seem to find any that are pre formed. I assumed that vacuum lines should not be soft but I could be wrong.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 24,246
    Some stores had vacuum line on a roll where they cut whatever length you wish to purchase.
    You need your size line as well as a length estimate.

    Some pieces may have been shaped from harder rubber when new but likely aren't available.
    You'll have to use various connectors.

    I do not know if any of the places like gmpartsdirect.com have blowup diagrams that show the various vacuum lines on engines that many years back or not.

    If you could find one in a recycling yard that might be a great source for some of the pieces.

    2014 Malibu 2LT, 2008 Cobalt 2LT, 2015 Cruze 2LT,

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