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    Thread: 2008 p0340

    1. #1
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      2008 p0340

      2008 Aveo, 50K on the car, 1.6L engine, 5 speed transmission, NO A/C
      I replaced the timing belt, spark plugs, and valve cover gasket (oil in the spark plug wells) just before 50K. I have a 2009 Aveo with the same engine-transmission combination, so I let the 2008 sit for a year but ran the engine several times over that year, and connected a battery maintainer on the 2008.

      In Jan 2018 I started driving the 2008 Aveo and noticed the fuel mileage dropped from 36 MPG in the summer time to around 28 MPG in January. This is normal because the cold weather calls for a richer air/fuel mixture, the cold thickens the oil and greases plus the refinery’s increase the amount of Heptanes (vaporizes faster than summer blend gasoline) and heptanes leads to lower MPG. Anyway the Heptane information was from a friend that works at an oil refinery. I know in past years when it was minus 15f the fuel mileage went down to 28MPG so I didn’t think it was abnormal because January was a bone chiller this year with lots of -0F days

      I have been driving the 2008 Aveo for 2 months when the check engine light (CEL) came on and the car started bucking when lightly accelerating. I got a P0340 code (camshaft position problem) on my Innova OBD-2 code reader. I replaced the camshaft sprocket position sensor, checked all 3 timing marks to make sure I installed the timing belt kit correctly and drove the car for a couple of days and the code came back. I drove the 2008 Aveo some more and the CEL went off for about day. The CEL came back on a day later, then went off for an hour, then came back on.
      If I let off of the throttle when coming up to a traffic light or behind a slower moving car and then accelerate a little, the engine bucks a time or two and then runs OK.

      I bought a second new cam sprocket position sensor and another new timing belt but I haven’t installed it yet. Today I removed the top timing belt cover again and all of the timing marks seem to be where they are supposed to be. I bought a camshaft sprocket tool that goes between the cam sprockets for a 1.6L Chevrolet but the metal cam sprocket holding tool halves do not fit between the sprockets so the tool must be for a different 1.6L Chevy engine. When I changed the original belt, the sprockets moved a little and if this tool I bought would have worked and fit, the cam sprockets can’t move while installing the belt. I borrowed a universal cam sprocket holding tool from O’reiily Auto Parts when I replaced the timing belt but it allowed the sprockets to move a little.

      The engine seems to have all of the normal power, but bucks when accelerating just a little. It might crank a little longer when starting but I haven’t noticed anything else that is different. I have not done a compression test. I have read the compression should be around 200PSI.

      I do have one concern about the timing marks. When I align the cam sprocket timing marks, the crankshaft mark is a little less than 1/16” from being exactly on the timing marks on the crankshaft and the notch at the front of the engine. I was wondering if anyone got a slightly short belt or the idler pulley might have been a fraction of an inch bigger. My thinking is if the belt was just a fraction shorter or the idler pulley was a little bigger, the crankshaft mark would be shy of where they were supposed to be. My first replacement timing belt kit and water pump was Korean. The timing belt I just bought was made by GoodYear. I haven’t installed the second replacement Goodyear belt or the 3rd cam position sensor yet but will be doing that tomorrow or in a few days.

      I read a couple of repair blogs where a crankshaft sensor replacement where you had to do a “re-learn” process but I haven’t read that changing the cam sprocket position sensor needed to have a re-learn carried out.

      The cam sprocket sensor has a 12V supply wire, a ground wire, and a signal wire. I haven’t measured the 12 volt or ground connections. I understand the signal wire value needs a scope to read the value. I also have not checked the Cam position wires for continuity from the sensor back to the ECM. I found some web pages for a 2011 European Aveo with a 1.2 and a 1.4 engine that have electrical schematic but not for a 2008 Aveo

      Anyone have a similar situation and managed to fix it?
      Would connecting a scope tell me if the position signal is out of time? I had a Marquett scope when I worked for an auto dealership back in 1985 but things have changed since then.
      I was looking at a dongle and an OBD-2 Android app for under $100 but I don’t think it would tell me much more than what my Innove OBD-2 reader would tell me. I am hesitant to spend the $500 to $2,000 for some of the scopes I saw Youtube videos of. The “BlueDriver” OBD-2 has several good write ups but I think it might not tell me that much more than the Innova unit I have.


      Summary
      2008 Aveo bought new, 50K miles, P0340 codes, bucks when lightly accelerating, 1 new cam position sensor, 1 new belt, checked the timing marks two times-off by 1/16” at the crankshaft when the cam sprockets are perfectly aligned, cam sensor wires visually check OK but no other tests. The car sat for 1 year, the engine was run several times, and drove Ok at first, then the CEL came on.



    2. #2
      Almost time to do my timing belt
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      Any chance the cam sensor wiring harness was damaged when you did the timing belt job? In any case, I suggest first doing a continuity test of those wires, from the cam sensor connector to the ECM connector. If the continuity is good, then check for ground and reference at the connector, and back probe (or use a wire-piercing adapter) on the signal wire. (all you'll get from that is a fairly steady voltage or frequency). If all of that tests ok, then you could do a complete test of the signal by taking it to a shop having a scope, instead of buying one.

      EDIT: After posting, I realized that I was thinking of the crank sensor, and that the cam sensor is different. So, all you need to do is test the pink wire at #1 for power, the black wire at #2 for ground, and then the remainder of what I wrote above applies to the signal wire at #3.
      Last edited by avguy; 04-30-2018 at 04:21 PM. Reason: Corrected information

    3. #3
      What's wrong with my car?
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      I rechecked the camshaft timing marks ans they were on target.

      Next I measured the voltage at the cam position sensor pinkish-reddish wire and got battery voltage. The ground terminal had almost zero ohms resistance. I started the engine and got around 2.5V from the signal wire. I removed the battery and disconnected and reconnected the wiring harness gang connectors from the ECM. I loosened the body and engine grounding wires and re-tightened them. I had a 3rd cam position sensor so i installed it.

      When I changed my timing belt a year ago there was oil in the spark plug wells so I installed new platinum spark plugs. Last week I used an ohm meter on the spark plug wired and the resistance was in line with specifications. This time there was NO oil in the spark plug wells.

      Before the car sat for a year and after the new timing belt kit my fuel mileage was around 36 MPG. After a year it dropped to 30 MOG, then 24 MPG when the temperature was -15f. When the weather warmed up to 60F, my fuel mileage was still below 30 MPG for several weeks but I only drive a couple hundred miles in a month. My last fill-up had me at 42MPG. Crazy because my best fuel mileage was 39.5 MPG going 65 MPH on the interstate.

      My latest symptoms are:
      NO cam position CEL light where before it would come on and then go off several times.
      The engine still bucks 2 times if the RPMs are low and I accelerate lightly.
      It seems like the more I drive the car in days, the less it bucks.

      I have a friend that inherited his dad's 2009 Aveo that sat for 3 years. I told him to drain the gasoline but he refused. He had several codes and the engine would not go much past idle sometimes and would even stall. He drove the car and used 3 tanks of gasoline and now the engine runs OK. He never did any repairs or parts swaps. My idea is these Aveos do not do well sitting. Has anyone else experienced some poor engine performances after the car sat for a long time.

      Engine on TDC, cam marks lined up
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      Name:  2 Aveo crank sprocket mark.jpg
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      Battery voltage at cam position sensor feed
      Name:  1 Battery voltage  at CMP.jpg
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      Ground resistance at can position sensor wire
      Name:  3 ground resistance at CMP.jpg
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      Spark Plug wire test 2K to 5K per foot
      Name:  8 plug wire #1 resistance.jpg
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      Last edited by OG-Lou; 05-14-2018 at 04:51 PM.

    4. #4
      Almost time to do my timing belt
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      Quote Originally Posted by OG-Lou View Post
      .... When I changed my timing belt a year ago there was oil in the spark plug wells so I installed new platinum spark plugs. ....
      There have been multiple reports from Aveo owners who had performance problems after installing platinum plugs, and which were resolved when they switched back to copper. I've never used them on our Aveos, so I can't confirm this myself, one way or the other. I also don't understand why platinum plugs would cause problems, but the reports were from reliable people, so I don't doubt what they said. Given that it's fairly inexpensive, you might want to try copper plugs to see if makes any difference on your vehicle.

      I've had my Aveo sitting for more than 2 weeks at times, and it never had any performance problems as a result of doing that. I'll also mention that my Aveo's MPG has been remarkably consistent over 13 years - around 30 in the Winter, and 32 in the warmer seasons, always using 10% ethanol 87 octane gas.

    5. #5
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      I re-gaped the old spark plugs that came with the car (when the engine was running perfectly) and still have the bucking (2 bucks) when I apply light to medium throttle pressure. If I only apply very light throttle pressure, the engine doesn't buck. (decelerating to slight acceleration engine speed under 1,500 RPM. At higher RPM it bucks less)

      I have two choices now regarding spark plugs, try different gaps and try new spark plugs. I say try different spark plug gaps because my old plugs had a gap of .046 so I set it to the minimum .040 I found a range of 040 - .044 on one site (Rock Auto) that sold Aveo spark plugs.

      Back in 1964 I worked in an auto repair shop and we had a spark plug tester where we could change some of the test inputs. The higher the air pressure we applied, the more the spark plugs failed. I don't remember if we could adjust the spark voltage or not. We also did some night time tests to see if there was any glow around the porcelain to steel shell base, which was how well the gas seal was between the ceramic and steel.

      What I found was most spark plugs failed the tests if the gap was correct (.035 then) and center electrode was rounded off. Square off the center electrode and remove a little ground electrode metal by filing it a little and it passed the test with flying/winning colors.

      More spark plugs failed as the air pressure was increased. Back then the debate was which brand of spark plug worked the best. Most popular brands were the same. I did find some no-name brand spark plugs had a glow between the steel and porcelain at night. Several engines at that time were completely visible so the glow test was easy to do. I will say the test device was fairly low tech.

      A couple years later the shop bought one of those big fancy automotive oscilloscopes. It was magic at first, then I learned a scope measures time and voltage. I transferred some of the knowledge I gained using the scope to hand held tools that measures voltage and resistance. The most applicable meter for spark plug wire test was how much resistance a plug wire had was the ohm meter. I marvel at how simple it is to test spark plug wires when I read how many people replace spark plug wires but never test them.

      Of course ohm meters do not replace digital scopes in some situations but with spark lug wires and wiggling the wire as several places,an ohm meter is a low cost way determine good from bad spark plug wires. A few times when I found a bad wire, I cut off an inch and re-attached a connector. It worked until I could buy new wires. In one shop we made wire sets from individual parts and a roll of spark plug cable that worked as well as an OE part. A special crimping tool was the key to making up a wire/cable that lasted.


      I read there was a recall on 2009 Aveos because the spark plug boots were defective but nothing on 2008 Aveos. My Aveo was built in 2007 around Sept.

      I bought a can of Mass air flow sensor cleaner but I haven't used it yet. I will look again for any air leaks.

      I have a reference to an independent repair shop with some sort of digital scope but have not contacted him.
      Last edited by OG-Lou; 05-14-2018 at 05:07 PM.

    6. #6
      Almost time to do my timing belt
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      An OBD realtime data stream reader might be a big help in diagnosing that bucking. It would enable you to see if the fuel trims are changing at the point the bucking takes place, and (if they are) if the trims are showing rich or lean. And you would also be able to find out if any misfires are being counted by the ECM. The Torque app for Android is a popular and less expensive choice, or there are readers available off the shelf as well.

      Also just an FYI that in 2009 the second gen Aveo began using COPs, and that's what that recall is for. So your 2008 could not be included in that particular recall.

    7. #7
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      COP=Coil on plug

      I found my book for my Innova 3120 and have been reading it. It does some freeze frame data. I still have to learn how to use the 3120. After I understand what I am looking at on the scanner and what I should be measuring, I will connect the 3120 and do a road test.

      I watched several Youtube videos about WiFi Android dongles that plug into the data port(DLC). Several people like the ELM327 ~$14.00, the BAFX 34t5 ~$25, the OBDLink MX ~$90, and most of all the "BlueDriver for ~$100.

      Does anyone have a favorite scanner under $200? I am leaning towards the "BlueDriver."

      I did re-gap the spark plugs to .044 and it didn't change anything. I ordered 4 new spark plugs, the same as came with the car.
      Last edited by OG-Lou; 05-16-2018 at 12:30 AM.

    8. #8
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      I connected my Innova 3120 code reader and found a new code but no CEL/MIL P0113 AIT=air intake temperature circuit 1, high input. The FF freeze frame data indicated the air intake temp to be -40f. The outside air temp was around 68f so i know the reading was off. I borrowed a Bosch code reader and it said the intake air temperature was 128f.

      So now I have to update my Innova 3120 or determine if it even works on streaming data for my 2008 Aveo. I bought the scanner used so maybe it was not working correctly (seems to read codes well) but the streaming data readings are way off. The RPM stays at 1,400 no matter and the road speed and the speedometer always reads 0 MPH.

      I tested the 5V (actually 4.8/9V) signal wire voltage and found 4.9V. The ground wire measured .1 ohm whis what my meter registers when I connect the 2 leads together. I put my meter on 2K ohms and the AIT sensor measured 16.4K ohms at driveway temp of around 78f. I removed the AIT sensor and used a hair dryer to heat the thermister. The ohms vary from 1540 room temp to 760 ohms when the ATI sensor is sort of too hot to hold in the hair dryer air stream/ That is about how it is supposed to work but i don't have the exact specifications.

      I watched several Youtube videos about how an AIT sensor works and how to bench test the sensor so in general my AIT sensor moves in the correct directions.

      On youtube "Scanner-Danner" "Schrodingers Box" and a few other guys really get down to testing circuits with mostly basic test instruments and explain the how and why things work. The both claim too many parts are thrown at a problem/s that really do not fix the issues a car is having. The videos are not quick fixes and require time and an understanding of the problem and how things work.

      I bought new spark plugs (50K on the old spark plugs) on eBay and they arrived today so I gaped them, applied a little anti-seize and installed the new spark plugs. The old #1 and #4 spark plug were a light tan but #3 & #4 where bone white.

      I had a lot of yard work to do so I haven't done a road test. I am also waiting on a cable to connect my Innova 3120 to my computer. It came with a 25 pin serial cable but all I have computer wise is USB and maybe an old 9 pin serial port. Yes the Innove 3120 is getting old and maybe it was never up-dated or it could be toast. Fingers crossed that an update works for my 2008 Aveo. If not that "BlueDriver" dongle looks like it will be my next purchase, UNLESS I find a Snap-on MODIS 4 channel $500 + leads. Snap-On sold today for $700. Another option is an older Pico Scope for $250.
      Last edited by OG-Lou; 05-18-2018 at 03:43 PM.

    9. #9
      Almost time to do my timing belt
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      Quote Originally Posted by OG-Lou View Post
      ... So now I have to update my Innova 3120 or determine if it even works on streaming data for my 2008 Aveo. ...
      I believe that your scanner is ok about that freeze frame data, given that the OBD code and the IAT sensor reading were consistent with each other. Keep in mind that freeze frame is single point-in-time data, and can't be validated or invalidated by subsequent testing. Try clearing the code and see if it comes back.

      ... The old #1 and #4 spark plug were a light tan but #3 & #4 where bone white. ....
      To me that's a bit of a red flag. You made a typo, but it's clear that 2 plugs were substantially different from the other 2. That's fairly unusual, and I suggest doing a compression test, just to (hopefully) eliminate internal mechanical issues.

    10. #10
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      Yes I made a mistake #1 & #4 spark plugs are light tan and #2 & #3 are whiter.

      It is cooler today and the car bucks less when the engine is cold with the new spark plugs but the buck isn't eliminated when the engine RPM is under 1,200 RPM and the engine is warmed up. The bucking is always a low RPM event.

      The whiter spark plugs in old cars indicates a lean mixture or an air leak. I haven't been able to see live data on my Innova 3120. I hope up-dating it causes it to work as new or maybe the Innova is too old to work on a 208 vehicle OR maybe that is why it was sold.

      RE: compression test in the plans when I find a compression tester with a long hose that fits down in the spark plug wells. I assume one pulls the fuel pump relay and disables the ignition coil pack.





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