2008 p0340

[avguy]

... 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.

I didn't bother disabling the coil pack. All I did was pull the fuel pump relay and then just let it stall out.

[OG-Lou]

I haven gotten to the compression test yet. I had several other things to do that had time limits.

I think my air intake temperature error P0113 code was due to me not getting the wiring connector pushed in all the way or starting the engine with the wire off. I cleared the code several days ago and it hasn't reset.

My air bag light has been on.

I did order a MaxiScan 903 Bluetooth OBD2 OBDII code reader. I think I will have it in 2 weeks. I bought the low price reader with the idea of buying something that might be able to much more later after I learn a few more things about OBD-2 and all of the optional modules on recent cars. I am investigating what type of scan tools can be had for under $600 to $800.

Things are more complicated since I worked for a car dealership back in 1986. I will admit to wanting tools and being able to use them properly even if it isn't all that practical or cost effective. OTH, if I pay someone to code parts so the car's computer to recognize the new part after a few times, it might pay for the advanced scanner cost.

I reconnected my Innova 3120 today and found the freeze frame data for a P0340 code that showed up again yesterday that didn't reset for 2 weeks.

freeze frame data Innova 3120 closed loop; load 26.6; coolant 183f; short term fuel trim 0%; long term fuel trim 5.4%; intake manifold 8.5 HG; timing 1*; intake air temperature 89f; throttle 13.3; engine RPM 866; MPH 33.

I might have been in neutral or had the clutch pedal to the floor getting ready to change gears or approaching a stop sign when the code was set. The strange thing is the car is almost back to running normal with only an occasional buck.

From what I read the difference in fuel trims might be an issue OR is an issue in 60% of driveability issues.. This is my first experience with fuel trims. I have years and years of experience with carburetors, rich-lean conditions, partially blocking the air intake to richen the mixture and/or adding some form of extra fuel to test for rich or lean conditions. I watched several "fuel trim education videos" but I do not claim I know what I am doing. Right now, learning a few basics is where I am at. I didn't have anything to see if the STFT changed and the videos I watched indicated a problem if a fuel trim was over 10

Over the winter my 10 yr old battery died so I charged it without disconnection the + or - cables. I also might have used jumper wires to start it. One friend said if he uses his car to jump start another car while his donor car is running it messes up his onboard computer/s.

[avguy]

... I am investigating what type of scan tools can be had for under $600 to $800. ...

That price range is WAY more than even the very best OBD realtime reader would cost (around $200 should be the top price). There are proprietary tools available which are quite a bit more expensive, however those are auto maker-specific and have no generic capabilities, and typically are purchased by the better shops who can get the required payback out of them.

... I reconnected my Innova 3120 today and found the freeze frame data for a P0340 code that showed up again yesterday that didn't reset for 2 weeks....

Nothing in the freeze frame data that you posted looks like a red flag.

... The strange thing is the car is almost back to running normal with only an occasional buck. ...

Given that the vehicle sat for quite a while, you might consider giving it a good 'Italian Tune-up' or two. May not eliminate the bucking, but won't hurt to give it a try.

..From what I read the difference in fuel trims might be an issue OR is an issue in 60% of driveability issues.. This is my first experience with fuel trims. ...

Fuel trims are fairly simple and straightforward. Ideally the Short Term FT numbers should fluctuate rapidly between small positive and negative numbers. Our Aveos typically stay inside of a +5 to -5 range, regardless of RPM. Long Term FT is similar, except that the rate of change is much less (constant numbers for longer periods of time). Anything outside of these patterns indicates some type of problem exists.

... Over the winter my 10 yr old battery died so I charged it without disconnection the + or - cables. I also might have used jumper wires to start it. One friend said if he uses his car to jump start another car while his donor car is running it messes up his onboard computer/s.

Although I've seen this same thing posted on other sites, I've never had a problem myself or know of anyone else personally who did either. But I also wouldn't doubt that it's a possibility.

[OG-Lou]

I used 3 more scan tools in the $200 price range. None show any codes for the SRS air bag light being on and no other codes are present, not even a camshaft position code. I was wondering if the P0340 code needed to be set only after a drive cycle was completed or could be only set after xyz miles were on the emission test sequences was completed.

The last code reader was a Harbor Freight ZR13 and it showed the short term fuel trim changes quite a bit along with the O2 sensor voltage changing a lot too. so I guess that part of the emission system is working as designed.

I borrowed a compression tester but it didn't work correctly. It let out the pressure on its own. The compression might have gotten up to 90# but it dropped to zero really fast. I bought a compression tester from Harbor Freight. It had 3 long hosed adapters. I think a compression tester with a shorter hose might read a few pounds higher. I only came up with 130# on all 4 cylinders. The first stroke gave me over 90#. All 4 spark plugs were out, the fuel pump relay taken out and the throttle pedal all of the way to the floor. I did the compression test with a warm engine and did not add any oil to do a wet test.

I was reading a 2009 Aveo thread and that person has 125# to 130# of compression. Here on the Aveo forum I saw a compression test with something like 175#, which seemed on the high side when compared to what I found on engines 25+ years ago.

I compared the old marks I made on my old timing belt and sprocket marks with where the extra marks are on the new timing belt and everything matches up. I have the timing belt covers off for the third time looking for something I didn't align correctly. I am tempted to remove the new timing belt. I already have another timing belt I could put on and see if it makes the compression readings go up. With the marks where they are in my introduction pictures, I don't see where a newer timing belt would make any differences. It seems like a waste of time to change the belt again. I haven't ruled out replacing the belt a second time but it doesn't seem practical with the marks being lined up.

I talked to a mechanic that worked for a Chevy dealer. He said the rural dealership where he worked at had an Aveo customer with a problem/s that lead to the dealership finally replacing the engine after replacing a bunch of other parts and nothing improved. Later, someone found an ABS code or service bulletin and once the ABS issue was fixed the car instantly ran normal. Another story I read that had a P0340 code and the car did not have a cam position sensor position part. The problem was a bad coil ground. In addition, I read a story where the crank sensor was flaky but the car had a P0340 code. I suspect a lot of miss diagnosis taking place because of the lack of proper testing, limited knowledge, limited proper equipment, lack of time or wanting easy answers, and the tremendously complicated emission systems.

I have the car up on jack stands and I see my two remaining 10 yr old OE tires have small bulges in them. They still have 3/32 of tread but they have to go. I bought 2 used like new tires and I have a tire changer and a tire static balancer. Surprisingly the 10 year old TPMS sensors still work well. I use a set of 4 winter tires so the OE tires do not actually have 51K on them but something near 40K is possible.

My 1951, 1958, and 1966 Chevies were much easier to diagnose. It was do they have spark, fuel and compression and those 3 things were relatively easy to determine.

[OG-Lou]

AVGUY, I had several auto parts guys say never have your engine running while jumping a no start car. Some say it is OK if your donor car is NOT running. I know from my GM auto training classes heavy draw electrical devices create internal spark called or related to what is called Transient Voltages that can go over 200 volts. In a starter the brushes arc/spark and that creates a high voltage. It makes sense to me because we did some tests in the GM classroom. I work on computer type circuit boards and wear a ground strap so i don't zap the integrated circuit chips.

I found the meaning of an Italian tune-up. I never heard that term before.

"Go out and thrash it (UK expression) a bit = Italian tune up!"

[avguy]

.... I only came up with 130# on all 4 cylinders. ....

That is WAY too low for a first gen Aveo. My '05 compression was 200 dry, and I'd expect at least 190 for any first gen engine in decent shape. You've said it runs well, and you did the testing correctly, so I'm suspecting that your compression tester is not making a good seal in the spark plug hole.

[OG-Lou]

Thanks AvGuy, yes 2 compression testers that gave low readings puzzles me. The Harbor Freight compression tester when coupled with an adapter hose is about 18" long. I have a 40 year old Snap-on compression tester but I couldn't find it. I tend to think I can remember when I last used it. I need to get things back in to my tool box. With the extra tools I bought in the last 10 years, they come in plastic cases and I don't have room for cases in my tool box so I keep them in various places. I got a kick out of fixing up bicycles and bought a bunch of bike tools. Maybe I have too many tooks OR I need to be better organized.

Good news, My Aveo is running much better. Here is what I did yesterday and today.

I took the top timing belt cover off and the crank pulley off again. I watched or read over 20 web articles about timing belts, sprocket alignment procedures and sprocket tools that have alignment marks so only an idiot could get the timing marks miss aligned. I did my cardboard cut out tool again (new cardboard) and every thing lines up. My marks are dead on so that can't be the problem.

With the battery out of the tray and the air filter housing removed, I saw a ground wire group behind each headlight, I loosened them and then tightened them.

While the battery was removed, I think I did a reverse Italian tune-up. I turned on the dome light to drain any charge in any capacitor that is connected to 12 volt system.

After reading and watching some videos of bad grounds on spark coils giving a P0340 code, I loosened and tightened the bolts on my coil pack.

I watched some videos about drive-ability issues so I decided to remove the throttle body and clean it with "throttle body cleaner." I read the ingredients of carb and choke cleaner and the throttle body cleaner had about the same ingredients. Throttle body cleaner is $2 more than carb & choke cleaner but I didn't want to take a chance so I went with the throttle body cleaner. I tried Mass air flow sensor cleaner but that didn't remove much of the black crud next to the tube going to the EGR port and on the back side of the throttle plate. I didn't move the throttle plate very much, just enough for the cleaner to flow around the throttle plate that was all but closed.

When I took off the front tires to remove the crank pulley I saw each tire had a bulge, so I replaced both front tires with some used tires I already had. That eliminated a wobble in my steering wheel when I was traveling around 15 MPH.

Why the car runs better?
Number 1, I am going to credit the better running to draining the electrical system(reverse Italian tune-up) when I removed the battery and turned on the dome light. I wonder if the computer remembered the problems the non copper spark plugs seemed to cause. The engine starts quicker and does not crank as long as when the engine was bucking.

Number 2, maybe loosening and tightening the 2 body grounds behind each headlight had something to do with the car running better but I loosened and tightened 3 or 4 other grounds, which some were between the battery ground and engine block, and other body grounds.

Number 3, maybe the crud on thew back side of the throttle body caused an imbalance in the low speed fuel and air control.

Number 4, could an out of round shake the engine enough to create a false crank sensor signal?

I may have things fixed or maybe not. The next 2 weeks or the completing of a test to pass emission certification should give me a clue. I don't know how many miles it takes to qualify for that inspection.

Some of what I did doesn't make logical sense so "your mileage will vary" (results will be different) if anyone tries it on their car.

[OG-Lou]

After watching more videos of synchronization and timing parts past 2 AM this morning, I saw a video of ' scannerdanner ' using a lab scope comparing the time signals from different components. It was related to late spark timing but the idea might work for the crankshaft signal when compared to the camshaft signal.

Laying in bed for a bit this morning I thought maybe when the engine bucked, the ECM interpreted the crankshaft rotating at one RPM and the camshaft rotating at a different RPM so the ECM created the P0340 fault code.

Number 5. So getting rid of the platinum or what ever spark plugs, cleaning the throttle body (the bucking was under 1,500 RPM) and draining the electrical system, may have all contributed to the car running better OR it could only have been one thing I did caused the car to run better.

One thing for sure is the code doesn't mean that actual part is bad but means the ECM didn't receive the signal as it was set up (PID) in the ECM. Maybe a fault code is triggered if one or several signals fall outside an expected variable values.

https://www.youtube.com/results?sear...=scannerdanner

[OG-Lou]

The P0340 code is back a week later after driving over 125 miles and the freeze frame data looks normal to me. The car runs well so I erased the code.

I bought a Bosch 1050 bluetooth dongle. It has live data for about 25 PIDs so once I learn how to use the device and learn where things are in the menu, I am going to remove cam position wire when the engine is idling and see if the P0340 code is triggered right away or try to determine if the error has to happen after some other event is completed.

If I was designing the cam position software, I would have the light come on the first or second revolutions of the crankshaft if the cam and crankshaft were out of synchronization. I wish I could do a crankshaft sensor re-learn but it sounds like a "Tech2 tool is required. Several stories I read said the aftermarket tools usually do not work (after 5 tries) and the people had to go to the Stealership to get the crankshaft re-learn to take hold. One guy on a Youtube video with a "Tech2" did a re-learn in under 5 min.

But I don't run the show at the manufactures and my paycheck is peanuts compared to the people who design this stuff.

[avguy]

... If I was designing the cam position software, I would have the light come on the first or second revolutions of the crankshaft if the cam and crankshaft were out of synchronization. ....

I'd expect that as well, and it's entirely possible that's exactly the way it works.

Have you taken a look at the ground wires and the big battery wire going to the fuse box? You want to keep in mind that all of this OBD stuff is electrical, and is totally dependent on getting constant good voltage from the charging system. So any electrical 'blip', even lasting for just a microsecond, might be enough for the ECM to flag a fault, simply because it didn't get a sensor reading when it was expecting one. And the bucking that you've previously described tends to fit in with that possibility as well. Perhaps there's nothing wrong with your vehicle, other than an occasional, sporadic, and very momentary electrical interruption.

I'm not trying to tell you there's definitely an electrical issue with your Aveo, only that it's in the mix. In any case, checking the grounds is a highly recommended thing to do for any issue which hasn't been diagnosed as being something else. But if you've already done so, then sorry for wasting our collective time with this post.