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Super rich

Discussion in 'EEK! - Every Extended-K Car' started by Chad_M, Mar 3, 2020.

  1. Chad_M

    Chad_M Active Member

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    Hello, my 87 gtc 2.2 turbo runs super rich upon startup when the temps are under 50f. Chugging, black smoke, raw gas smell and all. No codes, coolant temp sensor ok, even replaced it with no change. Full tune up in the last few years including new coil and pickup. This car has done this the last several years, run great all summer. Any ideas?

    Thanks, Chad
     
  2. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Could be the wiring to the CTS, or could be a bad MAP sensor. They don't always trip a code.
    Could also be a failing battery. Do a load-test and clean the connections. Measure the voltage with engine off after sitting overnight. A failing battery can throw off all the reference voltages for the sensor.
    How long does it take to run correctly after starting? And is it only on cold starts, or hot starts as well?
     
  3. AllanC

    AllanC Well-Known Member

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    Check and make sure the vacuum hose is in good condition from its attachment on the intake manifold and to the fuel pressure regulator. If that hose has failed the possibility exists for excessive fuel pressure at the fuel injectors and this will create an overly rich air - fuel mixture. Also it is possible that the fuel pressure regulator has failed and is not limiting fuel pressure according to the vacuum signal from the manifold.

    If that does not resolve the issue then you would need to connect a scan tool and look at the readings from the oxygen sensor and fuel trim values. Erroneous and constant lean fuel mixture values from the oxygen sensor can cause the electronic engine management system to over fuel (excessively rich) injector pulses. Also an exhaust leak between the engine and oxygen sensor can skew and fool the oxygen sensor to report lean air - fuel mixture and cause overly rich air - fuel mixtures to be generated.
     
  4. ImperialCrown

    ImperialCrown Moderator
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    You have the correct Champion RN-12YC Copper Plus plugs?
    Platinums or other types may misfire when cold.
     
  5. Chad_M

    Chad_M Active Member

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    Plugs are the factory champions, no exhaust leaks, map and cts sensors have been swapped with known good one from one of my other cars. When battery was new it did this, now battery is several years old, battery's on a tender during winter, so voltage is ok. I've smoked the vacuum system on the car and didn't find leaks, and when I have the scan tool connected O2 is switching normally. Issues only occurs under 50 degrees and will not clear up, engine eventually stalls, over 50 or so degrees it runs perfectly, probably drove it 2k just in the past year with no issues. Thank you for all your suggestions! Really has me stumped.
     
  6. AllanC

    AllanC Well-Known Member

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    You indicate that the oxygen sensor is switching normally. So is it switching between a reading between less than 0.45 volt and a reading greater than 0.45 volt every few seconds?

    What are the short term and long term fuel trim values? A normally functioning electronically controlled feedback engine management system should show trim values within a range of range of negative 10% to positive 10%. If you add the short term fuel trim and long term fuel trim values you should achieve a value very close or at zero.

    Did you check the fuel pressure regulator and its vacuum line?
     
  7. ImperialCrown

    ImperialCrown Moderator
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    I have had past issues with Bosch or 'Universal' O2 sensors, but they usually pegged high. If yours is switching, that would indicate to me that the mixture is staying within the threshold of the sensor.
    Is there a nice, blue-white spark? A yellow-orange spark might indicate low firing voltage. Are the plug wire terminals fully seated into the cap where they are adjacent to the rotor on the underside? Any 'dust' inside the cap? Does the carbon button have a shiny spot where it contacts the rotor?
    Cold misfire can mimic a rich mixture. Ignition system issues can show up more when cold.
    Does the black carbon fouling burn off the plug tips once it is warmed up?
     
  8. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Please take measurements of the battery voltage - after sitting overnight with charger disconnected; at idle immediately after cold start under 50F; at idle after it has warmed up and symptoms are gone; about 5 minutes after shutting off; and again after headlights have been on for 10 minutes while engine was off.
     
  9. dc8flyer

    dc8flyer Well-Known Member

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    I’d like to “smoke” my vacuum system but never knew how exactly. Can you tell me how you did the smoking?

    How old is you fuel injector? It may be worn out, the seal around it might be leaking air, etc..the wiring insulator to the injector might be cracked.
     
  10. Chad_M

    Chad_M Active Member

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    I will double check voltage on the O2 but it was switching lean / rich, voltage going up and down pretty quick once warming up. I did not think they O2 was monitored at first during cold start on these cars? O2 is possibly original, I've owned the car for a long time and never changed it. My OTC obd1 scanner doesn't show me fuel trims like my obd2 scanner on my newer cars does so I have no idea. Fuel mileage on the car stays in the mid 20's as it always has, my 86 & 88 lebaron with the same engine does the same, all automatic 2.2 turbos. Fuel pressure regulator holds vacuum and hose is good. Spark is bright white/blue last I checked (distributor pick up died and was replaced last summer), will take a close look at rotor and cap, they have been on their some time. I will check voltage also as Bob Lincoln recommended. These cars I usually smoke thru the main vacuum port on the top of the intake and the brake booster hose.
     
  11. ImperialCrown

    ImperialCrown Moderator
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    The O2 sensor is ignored in open loop until warmed and enters closed loop for exhaust oxygen content feedback to control injector pulsewidth.
    This may be too old for fuel trim readouts. The O2 sensor should switch 0 to 1 to 0, etc.
    Injector pulsewidth in mSecs may be readable?
     
  12. AllanC

    AllanC Well-Known Member

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    Check fuel pressure on fuel rail. I looked at service manual for 1984 2.2 liter turbo 4 cylinder and it indicates the engine should have a constant 53 psi on the system. Hopefully this is still a valid pressure for a 1987 model. Excessive fuel pressure could cause a rich air - fuel mixture.

    To check fuel pressure you will have to install a tee fitting to a pressure gauge and then install the inlet and outlet of the tee on the input side of the fuel pressure delivery to the fuel injectors.
     
  13. 85lebaront2

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    Your issue sounds very similar to what I had when I first started my project car, it would be pig rich shortly after starting. I do have the 4 wire O2 sensor on mine as it was highly recommended by the friend in Cary NC who helped me build the first one. The O2 sensor was the one I had installed in 2005 when it was built, I bought a new NTK one and installed it (loads of fun with the two piece intake) and the problem went away, the heated O2 sensors were developed to shorten the time between engine start and sensor "light off" to where it starts controlling the mixture.

    One more item to possibly check would be the coolant temperature sensor (two wire one on the thermostat area) if it goes out of range at 50° F it will definitely make it run pig rich until it gets back in range.
     
    ImperialCrown likes this.

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