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Thread: Vacuum Guage Connection

  1. #1

    Question Vacuum Guage Connection

    Where is the proper connection port on the intake manifold for a vacuum guage on a 97 Saturn 1.9 liter DOHC engine? The Haynes manual only says to connect to the intake manifold. It seems like disconnecting the PCV hose and connecting the guage in its place is the only suitable place on the manifold, but is that the acceptable location? Will not having the PCV connected affect the readings?

    Thanks

  2. #2
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    Hello Firebird14,

    Connecting your vacuum gauge directly to the intake manifold at the PCV hose connection port (no "T") will work fine. Idle RPM may drop slightly.

  3. #3

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    Thanks for the information. The PCV port worked fine and the vacuum readings came back within specification. However, I was hoping you could provide some additional advice.

    The symptoms I am experiencing are that the car starts and then immediately dies. Once it dies, it cranks but will not start. The only way I can get it started is to hold the accelerator to the floor and continue cranking until it turns over. This only occurs during COLD starts. Once the vehicle is warmed up, it starts and runs fine.

    I used an spark tester and found that each spark plug was receiving spark.

    Fuel pressure readings are within specification (both with vacuum applied at the regulator and without vacuum applied) and decay pressure is within specification. I used a stethoscope and all injectors are clicking.

    I then suspected a vaccuum leak at the intake manifold or throttle body, but as I stated above, vacuum was exactly within specification.

    Finally, there are no DTCs. Can you please let me know what I can or should test next? I am stumped.

  4. #4
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    Hello Firebird14,

    One area that you might consider looking at would be the IAC valve and related ports on the throttle body. Refer to Sections 14 and 15 in Chapter 4.

  5. #5

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    Thanks. I'll recheck the throttle body next chance I get. However, if the IAC valve was malfunctioning, wouldn't there be an accompanying DTC?

    On a related note, I had been suspecting a leaking fuel injector at this point. If any of the fuel injectors were leaking, would the fuel pressure decay definetely be outside specifications?

  6. #6
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    Hello Firebird14,

    Regarding the IAC valve, although the electrical circuits are fine, we were thinking that perhaps related ports may be clogged affecting idle when cold. You bring up another area of concern regarding leaking injectors. This could affect cold-starts by flooding the engine. Does the engine idle after you get it started by holding your foot down on the accelerator?

  7. #7

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    Regarding the fuel injectors: Yes, during an initial cold start, the only way to keep the engine from stalling is to hold my foot on the accelerator for a minute or two, and then it idles ok. Although, if injectors were leaking, woudln't the fuel pressure decay be out of specification?

    Regarding the throttle body: Would you recommend I remove the throttle body and thoroughly clean it and blow out the ports with compressed air?

  8. #8
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    Hello Firebird14,

    Well, one would think that if an injector(s) were leaking, the decay pressure would reflect that problem. After a bit of online research, it seems that some other folks have encountered a similar condition with their Saturns. It might be very beneficial to do some online research to see what they have done regarding this issue. ECT sensors and injectors have been mentioned. If it were me, I would make certain that all ports for the idle circuit were clean -just for good measure. Here is a link to a video that someone posted on cleaning their Saturn throttle body that may be helpful. http://www.youtube.com/watch?v=Pc5qCuQLmFE . Good luck and let us know what you find!

  9. #9

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    The problem turned out to be the ECT sensor. When I removed the ECT from the block and inspected it, I found a fairly large crack in the thermistor. I replaced the sensor with a new one and the car starts up every time now with no issues. Thanks for the additional information...much appreciated.

  10. #10
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    Hello Firebird14,

    We're glad to hear of your success!

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