Timing chain at fault in ’88 Cavalier?

dchroust

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!

desi501

If that chain is original it HAS to have a lot of wear. I don't know how much your missing by but chainging your oil almost always lowers HC's. At this point you probably have low compression, injectors with a lot of wear, valves that don't seat all that well and who knows what else contributing to this problem. The Cat, O/2 and module don't have much effect on HC's and it sounds like the odds are stacked against you. You may be able to squeeze more mileage out of that engine but meeting emmissions is probably a lost cause.

vidtech

you can check the timing chain for slop yourself.pull the distributer cap off.have a buddy watch the rotor as you work the crank shaft back and forth.use a socket and breaker bar.line up the timing mark on the balancer to TDC.slowly move the crank just enough to take up the slop in the chain(you can feel it).note the timing marks on the pulley which line up to the pointer.then SLOWLY move the crank in the opposite direction and stop as soon as your buddy just notes the dist.rotor begin to move.then check your timinig marks again and note how many degrees of slop there is.usually 5-6 degrees are more indicate a worn timing chain.you might have a worn out engine.you have incomplete combustion due to misfire.good luck,it is getting harder to keep older cars around when you can't get them to pass emissions.

Mr_Shiftright

I think you could also put a timing light on the engine to check for a very sloppy chain. The timing mark should "wander" all over the place under the light. But the other suggestion is also a good one.

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?

desi501

I wouldn't put a penny into that car. It's just too tired with almost 200K. It looks like all you guys are assuming he HAS a distributor. He could have DIS. That makes checking that chain a lot harder. With that mileage you can almost guarantee that chain is shot and so are many other things that will make it EXTREMELY hard to pass emissions. Like I said without emissions to worry about, I might fix it, but if it has to clear emissions, I wouldn't invest a dime. It's like throwing it away. Use you money toward a newer vehicle.