Smoke coming out of flex pipe

[johnlopez]

Hello everyone,
have a 2004 aveo 1.6 and one day when I was driving it began to stall. I was able to make it to my apartment and then decided to check. Check engine came on. I opened the hood and smoke was coming out. I let it settle for close to a year and few months since I have another car and from what I found online was a possible head gasket problem. I check and there was smoke coming out of the tailpipe (white). The car was having problems running and was dying after starting so replaced the coil and also the spark plugs along with the wires. After that the engine would actually run okay but the smoke was still coming out. I ordered a head gasket kit and decided to change it. I spent the last week an a half changing the head gasket and just finished today. For the moment of the truth, the engine started with no problems and the check engine light was not on. However, two things are happening right now:

1) there is a knocking coming from the engine which increase if I press the gas pedal. The knocking appeared before I replaced the head gasket and thought that it was because of bad oil (read somewhere that old oil might create knocking). This is the sound of the knocking: https://youtu.be/AgL0kiy2TCw

The head engine was resurface and they also checked the valves. What exactly they did with the valves? they said that they checked the pressure and something else but the guy clearly had no idea (cashier). Would this be a bent valve? (hope not because it was a long week to bring everything apart to do that).

2) There is still smoke coming out of the "engine". However, there is no smoke coming out of the tailpipe but the flex pipe. I am now thinking that that was in the beginning the issue and did not have to replace the head gasket. However, there is no check engine light on now and the car does not stalls. It runs (idles, has not driven it since it first happened) good but there is the knocking and the smoke coming out of the flex pipe.

I really need help asap. I need to fix it and I am not sure what it could be. When I put the timing belt back the gears were align almost perfect (There were like 2 mm off) and the crankshaft and piston number 1 was at dead top center. I might guess that there is a bad timing and might be creating the knocking? From what I know the car never overheated (the car does not have a temp gauge to know). I am thinking that there might be a vacuum leak? I just can't figure out what is the knocking and the smoking. This car has 67000 miles on it. Almost forgot, I heard that I need to empty the fuel tank and get new gas in it. The tank is almost full and that is a lot of gas that needs to be thrown away but would this be a cause for the knocking? Any help will be appreciated.

[avguy]

So exactly when did the knocking start? If right after the spark plug swap, then perhaps you used plugs with the wrong heat range.

[johnlopez]

Hi avguy,

Thanks for replying. When the car started to have problems and started stalling and dying there was no knocking sound. after a year I decided that was time to fix it so I tried to turn it on and then the smoke was coming plus the knocking. I maybe started the engine two more times for 5 secs and then proceeded to replace the head gasket. Spark plugs are new and got them from autozone. Tomorrow I will see if I can drop the tank, empty it and get some new gas in it and see if that might be the issue.

[xintersecty]

I bet it's the valve cover gasket. Remove a spark plug and see if there is oil around it. If so replace the valve cover gasket.

[johnlopez]

Hi xinterxecty, checked the spark plugs and no oil at all. Tried to empty the fuel tank but I had too much gas so empty almost all the way to 1/4 and put a gallon of fresh gas plus Chevron additive but still knocking sounds still there. I have been reading and it says that if the knocking sound increases with acceleration then it could be a fuel mixture/combustion timing problem.

About the flex pipe smoking I think there is a leak of coolant/freon because when I checked underneath, the AC compressor had liquid all over. I have to lift the car really high to see.

I am more concerned about the knocking... any help will be great.

[avguy]

Knocking from the lower part of the engine would be really bad news, so you need to identify where the noise is coming from. Best way to find the noise is to use a mechanic's stethoscope, but you could try a piece of wood or hose first. The fan will come on after idling for a while, so watch out for your hands and fingers!!!

AFA the leak, dry and clean everything off completely (top and bottom), run it, and then take another look. It will hopefully be obvious at that point where the source of the liquid is coming from.

[johnlopez]

Update:

Thanks avguy, I have seen you help a lot on this forum so that is really nice man. The knocking comes from the top 100%. I did a compression test and it did 190 190 95 190. The compression on all of them is good. Something new that came when removing the spark plugs was that there was oil on the well (I believe that is the part that creates the spark). And I noticed that there was a tiny bit of oil on each of the pistons. I cleaned the pistons before putting the head gasket so that is how I can see the little bit of oil. I read that I might need to change the head gasket (maybe what xintersecty said before, I thought he meant just to unplug the wire and check for oil around the spark plug while still in). I have another head gasket and going to get new spark plugs. Read that they might let pass oil if failing. Any thoughts about what could be the oil going into the combustion chamber? Once again the check engine light has not come on.

[Bad_Elmo]

Hi Johnlopez, it looks like you got a bad cylinder. If your compression test values are accurate the one with 95 lbs. of compression is bad. Can you perform a leak down test? That will clearly identify the issue. Bring the suspect cylinder to TDC, connect the guage to the spark plug hole and the other end to an air compressor. Pressurize and listen for the sound of air escaping. If you hear air escaping from the breather its a cylander/piston problem. If you hear it out the tail pipe - its an exhaust valve problem. If it is coming out the intake - its an intake valve problem. If it is bubbling out the radiator surge tank - its the head gasket. You can pick up a test kit for like 45 bucks at an auto parts store, some parts houses will even let you borrow one if you leave a deposit. I hope this helps you locate your problem.

[johnlopez]

Hello Bad_Elmo--> lol, I actually after seeing your post went ahead and re-did the test since the car was warm. all of them did max PSI of 199. I figure it would be 200 since I am not sure when that gauge was calibrated. I am still going to try to do the leak down test. I read about it but I have not a compressor or the tool. I will have to figure it out. I will check all the auto parts here.

As of the smoke, I think it stopped. It does not smoke anymore (visibly) but it still smells like electronics burning. I did see that right where the new thermostat connects to the hose that goes to the radiator was leaking so I made sure it was really tight and did not see any more the smoke. I am already home ( I have the car at my friends shop and worked on it all morning). I replaced spark plugs and did the same. The car runs good and check engine light is not on and it does not overheat. It barely got to 1/4 (temperature) since I just let it idle for a bit. I did moved it a little bit back and fort and did okay. Got this guy looked at it and he said that it is normal since I replaced the head gasket but to be honest doubt that guy knew about it. I felt I knew more about fixing the car than him. Anyways. It idles it does not hesitate but the knocking still there.

does any body know how to find out if the timing is off? For the aveo the two cram gears had to be align with the crankshaft and piston 1 TDC. When I move the crams to be align they were off by 2-3 mm and I moved one a little bit to make it perfect but it would not stay it would move. I just adjust the other gear along with the crankshaft and put the timing belt. When I spin the crankshaft twice they did align but as I said they were off by 2 mm give or take. Would be this the problem? This job took me a week and a half so to go back to that point is something I am avoiding but if that is the problem I will go back and re do it.

One more thing is that I read about checking the EGR since there might be a air mixture problem. What I did was that when the car was idling I disconnected the plug and the car did not show any difference. It ran the same with the same sound. I know that when you check a bad coil or wire you do that and you can tell when it is good or bad. Could that be apply to this part? should it have made a difference? it looks rusty and beat up but I already spending too much money on this car.

Thanks for the help and time reading this long posts...

[xintersecty]

does any body know how to find out if the timing is off? For the aveo the two cram gears had to be align with the crankshaft and piston 1 TDC. When I move the crams to be align they were off by 2-3 mm and I moved one a little bit to make it perfect but it would not stay it would move. I just adjust the other gear along with the crankshaft and put the timing belt. When I spin the crankshaft twice they did align but as I said they were off by 2 mm give or take. Would be this the problem? This job took me a week and a half so to go back to that point is something I am avoiding but if that is the problem I will go back and re do it.

More likely your timing was good. Once you put the belts on and align everything the timing looks slightly off as the intake cam if forcing against the slack in the belt. Once the belt tightens, the marks align. This picture was taken before the water pump was tighten down. And beside if your timing was off your compression numbers would be bad/combined with that special crunchy sound of bent valves.