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1999 Pontiac Bonneville starting/missfire issue

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  • #437125
    ryanshrp14ryanshrp14
    Participant

      This car has given us a lot of trouble. When attempting to start it, the engine cranks and fires as if it is trying to start, but will not completely start. Once when I tried to start it, the starter just clicked, nothing else. After a few tries, It eventually starts, and runs incredibly rough. It also shot out a large amount of grey smoke. After a few hard revs, It will run completely fine at idle. The Check Engine light turns on and off randomly, but it has done that ever since its present engine was installed. It is a ’99 Pontiac Bonneville with a GM 3800 series 2. This automobile is on its 2nd engine, the 1st died from a rod knock. Mileage on the 2nd engine is about 93,000 miles.

      I appreciate the feedback.

    Viewing 15 replies - 1 through 15 (of 30 total)
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    • #437126
      jacobnbr1jacobnbr1
      Participant

        I would check the grounds and make sure they are good.

        Be advised this car has a central grounding bar under both sill plates that rust and cause all kinds of crazy electrical problems.

        #437127
        Shaun_300Shaun_300
        Participant

          Sounds like the upper plenum is starting to leak coolant into the cylinders, these engines are very common for that problem, it’ll rot through right near the throttle body causing an internal coolant leak. If it gets bad enough it’ll hydrolock the engine. Sounds like it’s wetting the plugs the first few cranks and eventually starts, the smoke you see is probably burning coolant, once it’s burned out it’ll run fine. Coolant smoke is usually white.

          If it’s a darker color smoke it could also be injectors leaking down when the engine is off causing a flooding condition on initial start up.

          #437128
          dreamer2355dreamer2355
          Participant

            You could try a ‘clear food mode’ start to see if it is the engine flooding with fuel. Just crank the engine with the accelerator pedal depressed to the floor. It leans out the fuel ratio to 18.1:1

            Did you ever have the CEL codes retrieved?

            As for the starting issues, i would recommend a voltage drop test on the starting system.


            @Jacob
            – Thanks for the insight into that ground plate!

            #437129
            ryanshrp14ryanshrp14
            Participant

              The code for the light is a random cylinder missfire, but the light turns on and off at different times ever since the new engine was installed. i plan on checking to see if it is flooding out. It also supposedly has a new intake manifold. It does leak coolant, but it is not leaking into the engine. It also leaks a lot of oil as well.

              #437130
              jacobnbr1jacobnbr1
              Participant

                I think shaun nailed it. I would pull the upper intake and look for antifreeze in the lower intake valleys.

                Doesn’t matter if the intake is new if someone didn’t put the egr sleeve in the intake and the exhaust burnt a small hole through the cooling passage.

                #437131
                EricTheCarGuy 1EricTheCarGuy
                Keymaster

                  Those engines are known for intake gasket problems and the consensus seems to lean in that direction so it might be a good place to start. I would at least pull the codes first however just to see what you have.

                  #437132
                  ryanshrp14ryanshrp14
                  Participant

                    Thanks. The people that claimed to have fixed the intake lied to us a lot about this car, so I’m sure they didn’t put in the egr sleeve. My brother and I will be working on it today, and we will look at that. Maybe we can read the codes again as well. Thanks for the help!

                    #437133
                    rice400rice400
                    Participant

                      As i mentioned in another thread, if it is indeed the intake gasket make sure you buy the good steel fel pro gaskets instead of the OE gaskets, that way you wont have the same problem again. Also, I would highly suggest flushing out all that dex cool crap and put in good ol’ green antifreeze.

                      #437134
                      dreamer2355dreamer2355
                      Participant

                        If you use good ol’ green as Rice400 mentioned, don’t forget some of the ‘Green’ coolant has 2-EHA (same chemical as what Dexcool has) this making the green coolant a Dex-clone.

                        #437135
                        ryanshrp14ryanshrp14
                        Participant

                          Thanks for the idea on coolant. Update: Checked the radiator to see how much was added and it was completely dry, even though it was filled up about 2 days ago. I’m sure it must be the intake. I also started it up today, seems to be missing. I rev it up, doesn’t sound great. But it didn’t take it any time to start at all. I even restarted it a few times. I’m going to continue looking at that intake manifold. Thanks everyone for the help!

                          #437136
                          EricTheCarGuy 1EricTheCarGuy
                          Keymaster

                            Good luck and keep us posted.

                            #437139
                            ryanshrp14ryanshrp14
                            Participant

                              PARTIALLY SOLVED: My brother and I went to start it to get it in the garage to diagnose what was wrong with it. Turned the key, and the engine just clicked every try, wouldn’t turn over. Jacked it up, beat on the starter repeatedly with a hammer while turning the key, but it wasn’t working. We began to think that the engine was hydrolocked. Pulled 2 plugs, noticed evidence of burning coolant. We tried beating on the starter some more but it still didn’t help. My brother noticed that the bendex (correct my spelling) gear on the starter motor would not disengage. It seemed to be stuck in the flywheel. We took a flathead screwdriver and tried to disengage it by hand, but we didn’t succeed. We believe that the starter motor is locked up. We are going to try to replace it, and hopefully that solves our starting issues, but it still doesn’t explain why we found burnt coolant on one of the plugs. Hopefully when we fix the starter we can fully diagnose what is going on inside that intake. Thanks everyone for the feedback and I will try my best to keep you updated.

                              #437140
                              twiggytwiggy
                              Participant

                                I think the reason the starter won’t disengage is due to the engine being locked up.

                                #437141
                                dreamer2355dreamer2355
                                Participant

                                  You could use a breaker bar and a socket on the crank pulley and try to rotate the engine manualy. If it doesnt turn over, take out all the plugs and try again.

                                  #437137
                                  Shaun_300Shaun_300
                                  Participant

                                    Make sure to replace the upper plenum if you plan on fixing it. If you just change the gaskets you’ll have the same problem. The plenum itself rots out. May as well do the lower intake gaskets while you’re in there too.

                                  Viewing 15 replies - 1 through 15 (of 30 total)
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