By on July 31, 2009

TTAC Commentator stingray writes:

My friend has a 2002-2003 Opel Corsa. In fact it’s “Made in Brazil.” I think it has GM’s family 1.6L 4 cyl engine. And here in Venezuela, this Opel is sold as the Chevrolet Corsa.

It’s throwing code 43: O2 sensor, lean mixture. Has a popping in the exhaust. I got the code using the MIL lamp and recommended that he change the air filter, fuel filter and clean the injectors. He did clean the injectors, also changed spark plugs, wires, coil and O2 sensor. Doesn’t know much about car fixing so got a bit PWNED on that. And the popping still continues . . . and the code too.

Sajeev replies:

I’m not sure which (American) OBD-II trouble code applies to the two-digit fault presented here.

So let’s speak in generalities, because “engine running lean” requires a loaded answer. Which makes me wish I was a mechanic by trade: a bad one that’s more than a little ignorant, too. Then, I’ll go buy a flat screen TV with my earnings. Because that’s how rich you can get by throwing parts at this problem.

But a fundamentally sound mechanic goes back to the basics, reading up on factory service information. Then he (or she, I don’t judge) checks these items, in this order: fuel pressure, TPS voltage, EGR position sensor voltage and proper operation of the EGR valve by using a vacuum pump.

Best and Brightest, did I miss anything in this diagnosis tree?

[Send your technical queries to [email protected]]

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16 Comments on “Piston Slap: Breaking the Code: Opel Corsa Engine Troubles...”

  • avatar

    “Popping in the exhaust”? Do you mean backfiring? If it is backfiring I would think you are getting unburnt gas in the exhaust. Could be timing, misfiring, ignition module.

  • avatar
    Greg Locock

    Sounds more like a leak in the exhaust manifold (or thereabouts) to me.

    My reasoning is that extra air must be present for a backfire to occur, since the mixture must be rich up until that point otherwise there is nothing to burn. This theory is at least compatible with the sensor code.

    So, cracks in the manifold, or a bad seal somewhere, eg manifold to downpipe.

  • avatar
    bumpy ii

    Start with the easy stuff. Unplug and remove the MAF sensor, then spray the inside with lots of electrical contact cleaner and swish it around and let it run out of one end.

  • avatar

    Need to reset the ECU… it may have adjusted itself to deliver more fuel due to the abnormal lean reading (which would cause the popping both before and after the O2 replacement.

    It would be easier if you go to a mechanic with an OBD-reader so you can see what the fuel trims are.

    Oh yeah… agree with Bumpy… clean your MAF.

  • avatar

    Does the car lack power relative to before this started occuring? Does it now run rough? The items attended to most likely won’t cause (or resolve) random popping like this unless it accompanied by a rough idle, notable loss of power, etc.

  • avatar

    Intake leak? Somewhere after the MAF sensor, possibly intake gasket (not that GM ever has problems with those, right?), intake plenum, or the plenum boot. That’s my guess. The old school way to check that is with a garden hose. I’ll leave it at that.

  • avatar

    Hears like a backfiring…

    It’s lacking power, didn’t report any rough running nor sluggishness (I expected the last one).

    At idle, it feels rough.

    Diagnostic connector is not OBD-II.

    The reasoning behind recommending him changing the fuel filter is related loosely on the fuel pressure argument: a clogged filter causes such condition, but it’s not the only cause.

    I told him to check that based on my own experience… I sometimes get a similar code in my car. Not a Corsa by the way.

    The guy took the car to a “mechanic” who performed all the work I mentioned. Local mechanics tend to do that. They’re kinda more brujos.

  • avatar

    Check for cracks in the MAF hose. It might look okay but close to the intake manifold gets hot and cracks.

  • avatar

    I have a similar problem with my VW 1.8t. I have been trying to track down the issue for quite some time. I have changed the plugs, coils, engine temp sensor (was bad), pre-cat O2 sensor, MAF, tried better quality fuel, seafoam detergent, everything.

    I just last weekend found the culprit… When I swapped out the timing belt, I set the valve timing a bit retarded (not ignition, but that could be your problem too). The problem did NOT start right after I made the mistake, but several months afterwards. If you have had the t-belt swapped you might want to check this or your crank position sensor (if its ign. timing that is off) as well as the other things mentioned in this tread.

  • avatar

    Popping sound in the exhaust usually means a burned valve. How did it get that way? A leak somewhere on the intake side, causing a lean condition that has been going on for a while. Usually one of the intake boots has a crack, typically along one of the accordian sections. Check compression in all cylinders.Repeat, squirting a small amount of oil in each cylinder. The one that does not improve is usually the culprit. JMHO

  • avatar

    Thanks a lot to all. Will go back and check with him.

  • avatar

    Sajeev is almost right with his flow chart, but he left out the very first thing- is the basic engine sound?
    BMWfan has it right: the Corsa has a leaky valve.
    The culprit can be quickly found with a leakdown test (pressurizing the cylinders with air) which should take about 15 minutes to perform. As for the rest of the wild-ass guesses, let this be a lesson: I turned wrenches for 10 years and most of the drivabilty problems I ran into were not caused by the electronic control system and none were solvable without a logical sequence of tests. Along the same lines, no engine management system can pinpoint a failure- it can only tell the tech what the engine is doing wrong- in this case the leaky valve is forcing a lean condition.

  • avatar

    Before declaring it a leaky exhaust valve, I would ask if the popping is constant or intermittant? If it is constant a leak down test would confirm the valve issue. The popping/lean issue could also be the result of a simple vacuum leak.

  • avatar

    See… if the O2 sensor was faulty, it could have thrown all the fule trims off… and the cheapest thing to diagnose would be to reset those. And the cheapest thing to fix would be a faulty MAF (a can of silicone-based contact cleaner works)… then you can work your way down to the more exotic possibilities… though a leakdown test isn’t that expensive, there’s no sense assuming the worst if the problem is occuring right after an O2-sensor throws a code.

  • avatar


    A) Randomly throwing parts at the problem based on cost is bad practice. You’re never going to be sure you fixed the problem or just masked it. I cannot count the number of times a car came in on the hook with a lot of owner-replaced parts when the cause was something simple, like a corroded battery terminal.

    B) Silicone-base ANYTHING should not be used anywhere near an engine- the silicone will poison the O2 sensor in a heartbeat.

  • avatar

    Granted… I didn’t actually know that… thanks for the tip… although I do remove the MAF completely when I clean it and let the solution drip out… haven’t had a blown O2 yet.

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