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Timing chain at fault in 88 Cavalier?
At 183,000 miles the car became subject to emissions testing and failed. New EGR valve eliminated NOx emissions, but hydrocarbon levels remained about 2x over limit despite new spark plugs and wires. Fuel filter is fairly new, fuel injector clean, compression ratio excellent, and the car’s twin coil packs (in lieu of distributor) evidently do not normally need replacement. Two well-meaning mechanics now suggest the timing chain, which is original, as the next likeliest cause, but local Chevy mechanic doubts this, says Cavalier would likely “skip” and hardly start if chain were stretched from high mileage. (He still recommends changing the timing chain, which is not subject to a manufacturer’s replacement interval, as a matter of maintenance.) I would pay $320 for a new timing chain if I had certainty that it would eliminate the excessive hydrocarbon emissions.
Unfortunately, I understand that at least the following three items, which I already replaced once before, may be at fault:
Catalytic converter (replaced at 63,000 miles in 1994).
Oxygen sensor (replaced at 66,000 miles in 1994).
Ignition control module (replaced at ca. 80,000 miles in 1996).
However, I replaced the latter two items because the “service engine” light was on, and it is not on now. As for the catalytic converter, my recent success in eliminating NOx emissions suggests that it still works.
A symptom: hesitation or momentary loss of power whenever I first step on the gas pedal and then again during shift from first to second gear as I accelerate. I neither feel nor hear anything like a misfire, which would presumably be hard to overlook in this four-cylinder (2.0L) car. I am reluctant to invest much more than the cost of a new timing chain in a car that will be junk if its original transmission fails soon. How likely is a new timing chain to eliminate my excessive hydrocarbon emissions? The local Chevy mechanic gave me the impression that the cost of inspecting the chain is not much less than getting a new one!
Unfortunately, I understand that at least the following three items, which I already replaced once before, may be at fault:
Catalytic converter (replaced at 63,000 miles in 1994).
Oxygen sensor (replaced at 66,000 miles in 1994).
Ignition control module (replaced at ca. 80,000 miles in 1996).
However, I replaced the latter two items because the “service engine” light was on, and it is not on now. As for the catalytic converter, my recent success in eliminating NOx emissions suggests that it still works.
A symptom: hesitation or momentary loss of power whenever I first step on the gas pedal and then again during shift from first to second gear as I accelerate. I neither feel nor hear anything like a misfire, which would presumably be hard to overlook in this four-cylinder (2.0L) car. I am reluctant to invest much more than the cost of a new timing chain in a car that will be junk if its original transmission fails soon. How likely is a new timing chain to eliminate my excessive hydrocarbon emissions? The local Chevy mechanic gave me the impression that the cost of inspecting the chain is not much less than getting a new one!
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Comments
I doubt that's the problem however, so I agree with the other guys that the timing chain is not a good diagnosis nor will it cure your problem.
You have to start with the probable first, not the remotely possible. The remotely possible is the last thing you try.
I'd try the oxygen sensor for sure. It's long overdue and so is your catalytic converter. That's where I would go after you've done the simple tune up stuff.
How's the air filter by the way? Got any vacuum leaks?