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  • P0303 and P0171, Engine Vibrations

    Hey Everyone,

    I have a 1999 Ford Contour V6 SE MTX with about 107K miles on it. For years I've used this site and NewCougar.org to do a lot of work on this car. Finally, I've run into a problem I just can't seem to solve with plain old searching. It is a little complex - so sorry for the long post.

    I got a P0171 (Lean, bank 1) and rough vibrations coming from the engine and then a P0303 (Misfire on 3). I figured "Fuel, Air, Spark" and started testing.

    Spark:
    • Ran engine, pulled #3 wire, no change in engine RPM or behavior. Any other wire pulled caused it to noticeably stumble.
    • Checked cylinder 3 for spark - yes and ouch
    • Pulled spark plug 3 looked ok, but old
    • replaced all plugs anyhow with new Motorcraft plugs
    • Tried an old coil pack I had around - same results
    • Spark seemed ok, and none of the above changed anything about how it ran. I decided to move on to Air.

    Air:
    • Full cleaning of the upper and lower Intake Manifold (following usual process on the site)
    • New UIM and LIM gaskets
    • New Idle Air Controller gasket
    • New throttle body gasket
    • New EGR gasket
    • While I was doing the UIM and LIM cleaning, I decided to take on a few potential Fuel issues since I had the fuel rail apart anyhow.
    Fuel:
    • New Fuel Pressure Regulator and gasket
    • Replaced all fuel injectors with flow matched, reman ones from injectorrepair.com
    • New fuel filter
    Same result, though. It runs, no ticking, no knocking, but with a clear vibration that is especially bad around 1750 RPM. I am still getting P0171 code and if I drive it for a mile or two, I get the P0303. Just for background, here's some data around what I am seeing:
    • Fuel Pressure at Idle on rail test port: 48 lbs
    • Vacuum at Idle: 18 in/hg (very steady)
    • LTFT at Idle: way, way lean 25+
    • STFT at Idle: 14
    There is more information I can give, but I think those data points are the most important - and this post is huge already.

    Can anyone suggest what else I can try? Would a compression test help? Any ideas appreciated and thanks in advance!

    -Mark (Delkra)

  • #2
    Did you check the resistance of the plug wires? Usually they will be 2,000 to 4,000 ohms per foot, but you might find #3 to be much higher.
    Inspect the length of the plug wires for any damage to the insulation.
    Check the plug boots and tubes VERY carefully for carbon tracking, #3 may have some tracks on the outside of the boot.
    If all the above doesn't turn up anything, pull all the spark plugs, block open the throttle plate, run a compression test and report back.
    I collect Ford's Red-headed step children.
    1985 SVO Mustang (turbocharged track rat)
    1989 Taurus SHO (supercharged track rat)
    1999 SVT Contour (Sedanus-Grocerygetter-Rapidus)
    2008 Mercury Milan Premier (Comfy boat)

    Comment


    • #3
      Thanks for reading the "book" I wrote in my first post. I ordered a set of brand new wires (Denso 671-6092) which got here today, but I haven't put them on yet. That should eliminate the wires as a source of trouble, but I can check the old ones for tracking too. I will install the new ones tomorrow and run a compression test while I am at it.

      Can I run a "cold" compression test (because #3 will not heat up since it seems to be a dead misfire)? Should I add oil to the top of the cylinders?

      Also, just to note, I did pull the valve covers while I was in doing the intake manifold. I felt around on each lobe of each camshaft on both heads, including over #3. The lobes are all there and neither the intake nor the exhaust valves over #3 appeared damaged, bent or stuck. I attached a picture of the front head, just for reference, but I have details on the rear (1-2-3) head as well.


      Comment


      • #4
        Originally posted by delkra View Post
        Can I run a "cold" compression test (because #3 will not heat up since it seems to be a dead misfire)? Should I add oil to the top of the cylinders?
        It would be better to have the engine warmed up for a compression test, if you can take it for a drive long enough for the coolant thermostat to open without the #3 miss bothering you too much, but you can do the test with the whole engine cold as well, I've done both, being consistent about the test is more important than the temperature of the engine.
        Usually you only add oil to the cylinders if you're looking for bad rings: You would run a compression test "dry", then add oil and run it again "wet". In your case, just start with dry and see where that takes you.
        Good luck, maybe the new wires will fix it and you'll be done.
        It looks nice and clean under the valve cover, you run synthetic oil?
        I collect Ford's Red-headed step children.
        1985 SVO Mustang (turbocharged track rat)
        1989 Taurus SHO (supercharged track rat)
        1999 SVT Contour (Sedanus-Grocerygetter-Rapidus)
        2008 Mercury Milan Premier (Comfy boat)

        Comment


        • #5
          Ok, I can try driving it around my neighborhood to get it warmed up a little. I don't want to risk any damage to the pre-cats or anything, but I doubt a little driving is going to cause too much of an issue. I hope you are right on the wires though.

          I've been running semi-synthetic in the engine for a number of years now and I am good about following the oil change intervals. Honestly, though, I was pretty surprised at how clean things looked too. The other head is just as clean. This car's been in my family since it was new -- and want to keep driving it, so I hope this issue isn't something catastrophic.

          Another question for you, though... Why am I getting a P0171 first and then the P0303? What I mean is, I am seeing the fuel trims go off-the-scale lean on both banks (but leaner on bank 1). Let's say #3's spark is grounding out because of a bad wire. The unburned air/fuel charge would get pushed into the exhaust stream... Could the oxygen sensor be seeing that unburned air/fuel and the computer interpreting that as lean? That unburned charge would be mixed with exhaust from #1 and #2, but still there'd be a lot more oxygen in the stream overall.

          Hmm... starts to get complicated, but anyhow, if there were a massive vacuum leak, I think it would probably causes misses on more than just one cylinder or even an outright stall.

          Comment


          • #6
            With a reported misfire you should replace the plugs and wires at the same time. Chances are there is carbon tracking on the plugs and wires. You might have ruined your new plugs. Coil packs are normally not an issue.

            As for the P0171 if you can monitor the sensor readings that is helpful. But if the O2 sensor is original its time to replace them. This should take care of the code.
            - 12 Focus SE
            - 99 Contour SeVT <- 3L/NPG Turbo
            - 2k Contour SVT - #2137

            Comment


            • #7
              Good suggestion on the upstream O2 sensors, I wondered how old they are, but usually when they get that decrepit, you start getting other codes about sensors not switching, etc. If the upstream O2's are over 60K miles, it's best to replace them and make sure to do a PCM reset so you start with fuel trims that aren't off in the weeds.
              I would also look at the fuel pressure again, and make sure the sure the fuel pressure regulator is working correctly.
              I collect Ford's Red-headed step children.
              1985 SVO Mustang (turbocharged track rat)
              1989 Taurus SHO (supercharged track rat)
              1999 SVT Contour (Sedanus-Grocerygetter-Rapidus)
              2008 Mercury Milan Premier (Comfy boat)

              Comment


              • #8
                Here's a question, how can you tell if injector #3 is getting a signal to "squirt"? What kind of volt or milliamp signal should you see at the connector when running? I would want to verify that before going any further.
                2k SVTC - Black / Praire Tan, blu_fuz ported 3.0L, 58k motor, 118k chassis

                http://www.contour.org/ceg-vb/attach...chmentid=16333

                Comment


                • #9
                  gunked fuel injector. or check that spark wire. waiting on result
                  1999 Mercury Cougar Full 3.0L MTX
                  236HP

                  Comment


                  • #10
                    oh yea you need to do compression test before anything else
                    1999 Mercury Cougar Full 3.0L MTX
                    236HP

                    Comment


                    • #11
                      Originally posted by ScotSHO View Post
                      Here's a question, how can you tell if injector #3 is getting a signal to "squirt"? What kind of volt or milliamp signal should you see at the connector when running? I would want to verify that before going any further.
                      You would need an oscilloscope to see the very narrow injector pulse at idle, but you could put an LED and a 500 Ohm resistor in series and put this circuit across the injector and you might see the LED pulse when the injector fires.
                      I collect Ford's Red-headed step children.
                      1985 SVO Mustang (turbocharged track rat)
                      1989 Taurus SHO (supercharged track rat)
                      1999 SVT Contour (Sedanus-Grocerygetter-Rapidus)
                      2008 Mercury Milan Premier (Comfy boat)

                      Comment


                      • #12
                        Originally posted by aboythatskates View Post
                        gunked fuel injector. or check that spark wire. waiting on result
                        He replaced the fuel injectors.
                        Replaced all fuel injectors with flow matched, reman ones from injectorrepair.com
                        I collect Ford's Red-headed step children.
                        1985 SVO Mustang (turbocharged track rat)
                        1989 Taurus SHO (supercharged track rat)
                        1999 SVT Contour (Sedanus-Grocerygetter-Rapidus)
                        2008 Mercury Milan Premier (Comfy boat)

                        Comment


                        • #13
                          Sorry for the slow response. It's a good news / bad news deal. Bad news, the new wires didn't make a difference. Here's the good news, I finally got a chance to do the compression test. I did a dry, cold test with the throttle blocked wide open, fuel pump fuse out and all plugs out. Here's what I got:
                          Cylinder Compression (PSI)
                          1 160, 180
                          2 165, 190
                          3 180, 200
                          4 170, 185
                          5 170, 175
                          6 175, 190









                          The first (lower) numbers were all from 3 compression cycles of cranking. For the second, I did 4 compression cycles. So from the results, I don't think it's a valve or rings issue. I took a pic of the test values to keep it straight.

                          I have a noid light set that I borrowed from a neighbor. I am going to try that out over the next couple of days. If it isn't that, I really have no idea what else it could be.

                          I'll definitely post the results here either way.

                          I am going to pull the upper intake off and check the wiring with the noid lights. Can I reuse the UIM gasket? It's brand new because I just the put whole thing back together (so I could pull it apart again)...

                          Comment


                          • #14
                            Wow, thanks. I learned what a noid light is. And here I thought THE NOID was that guy you wanted to avoid when ordering pizza! Just my guess, I think you are ultimately going to find an injector wiring issue.

                            And I would say yes on the UIM gasket, but I am a cheap SOB. Inspect the metal sealing surfaces, and if the gasket isn't compromised, then you'll be fine.
                            2k SVTC - Black / Praire Tan, blu_fuz ported 3.0L, 58k motor, 118k chassis

                            http://www.contour.org/ceg-vb/attach...chmentid=16333

                            Comment


                            • #15
                              Originally posted by ScotSHO View Post
                              And here I thought THE NOID was that guy you wanted to avoid when ordering pizza!
                              Oh man, you must be around my age. That's the same thing I thought when I first heard about the noid lights. I miss commercials from those days.

                              Either way, I really, really hope you are right on the wiring issue. I am not sure what else it could be. I know BrApple and others were talking about O2 sensors, but both of my upper ones are around 4 years old. The originals lasted a long, long time. Plus, I know the miss is there, even in open loop.

                              Anyhow, I'll make sure to report back after I get the noid light testing done.

                              Comment

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