# loss of power... Maybe limp mode?



## ChevyGuy (Dec 13, 2014)

I don't think this would be a tune issue, but I'd leave things stock for a few weeks to see if the problem returns.


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## NickD (Dec 10, 2011)

Before fuel injection, with a carburetor with a large 455 CID engine with a single cylinder misfire, would barely know the difference, still would go 70 mph. In the USA first emission control device was just adding the catalytic converter. With one cylinder misfire, would get raw gas into the cat, this would toast and plug the cat restricting the exhaust, sure would know the difference then in performance.

With the introduction of fuel injection, an O2 sensor was added and with a four cylinder engine, with a single misfire it would see excessive oxygen, think the engine was running lean, and enrich the fuel to all the cylinders further impeding engine operation. With some vehicles, barely could hit 36 mph, pardon my English. 

Engineers knew this, talk about political electronics, insisted on using one O2 sensor per cylinder, but for a four, would quadruple the electronics, but would still toast the cat. Still burning carbon, builds up on that center electrode insulator shunting that spark back to ground. Some guys were smoking crack insisting on a large spark plug gap.

In reality, ignition points were far superior, that so-called condenser would resonate the coil a produce a spark line, a number of spark pulses. With solid state, just enough to replace the points, only one single tiny spark, and the off time of transistors was longer that a set of points opening. Your spark plugs have to be clean and that gap has got to be small. Recommended gap is 28 mils, 25 even works better. 

But not the only problem, fuel injectors and PCV pumping blowby past the injectors, also builds up carbon on the face of these affecting the spray pattern, they have to be cleaned. With throttle by wire, that servo motor doesn't have near the torque of a return spring, can also restrict the closing of that vane.

A temporary problem is getting some water in your fuel, definitely causes a misfire. Spark plug cannot ignite moisture, still stresses the catalytic convertor, depends on the amount of water in the fuel, for fire reasons, practically all fuel tanks are buried underground.

Yet another newer problem are fuel evaporative systems for getting water in your gas. In a sense, an overkill, carburetors had a vented fuel bowl, FI is a closed fuel system. To save the cost of a line, the carbon canister was move high off the firewall and behind the tank. Exposed both to road salt slush and rain puddles, in theory, that carbon canister is suppose to collect fuel tank fumes, when the vehicle warms up, the purge valve opens and sucks in those fumes into the engine.

But when that canister is soaking wet, also sucks in moisture, what were they thinking?

In the USA, only requirement to become the head of the EPA is to help the president get elected, having engineering knowledge is not a requirement. But the same holds true for marketing, all you need here is a good line of BS. And you wonder why we have problems. 

Could never push a capacitive ignition discharge system, just barely enough to replace the points. Dey all do dis.


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## obermd (Mar 3, 2012)

Leave the tune off and see if the problem returns. Aftermarket tunes push the physical hardware harder so they show "weak" spots in the hardware faster. Your car has a problem and it is now only a matter of time before it returns and can be seen by a dealership service department.


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