Oldsmobile Delta 88

Question: 1992 Oldsmobile Delta 88

Vince, I have a 1992 Oldsmobile Delta 88 Royale with, 130,000 miles. All fluid levels and filters maintained normally.

Problem primarily noticed during hot summer weather; although it has happened during cooler winter weather, it just takes much longer to occur, so I know its temperature related. If the car has been sitting in the sun for several hours, and is cold started, the engine starts/operates normally.

After approximately a half hour of, operating temperature normal, at highway speed, if I try to accelerate at a reasonable rate, the car feels as though the engine is not firing on 1 cylinder, or similar to a slug of water in gas, but car does accelerate, just roughly. If I try to accelerate at a high rate, pedal to the metal type, the transmission down shifts normally and the car accelerates normally until reaching new operating speed where rough running starts/is noticed.

To distinguish this from a potential transmission problem, I've noticed when rough, surging starts, at highway speeds, if I let off the accelerator and then reapply normal pedal pressure, rough operation seems to diminish.

I can't seem to get the local shops to get the car to reproduce the symptoms because of the time dependency (temperature issue), although I think part of their problem is during hot weather they prefer engaging the air conditioner, which also seems to mask/diminish the symptom. Otherwise, all other operations are normal and no check engine lights illuminate. Any idea where/what I should look?

Regards,

Jim

Answer: I think you might have a problem with carbon tracking. This engine in the 1992 and 1993 Oldsmobile 88 and 98 models were prone to this.

Carbon tracking leaves dark lines, possibly looking like cracks, permanently etched into the spark plug ceramic and rubber of the boot. Carbon tracking cannot be rubbed or cleaned off by any means.

Higher peak cylinder pressures require higher demand voltage for spark plug operation. Higher demand voltage increases the stress on the spark plug to spark plug boot dielectric interface, such that contamination and air gaps between the spark plug and boot can cause this interface to breakdown. A break in the dielectric interface can allow the spark to find a path to ground other than the center electrode. These paths or carbon tracks are etched into both the spark plug and the spark plug boot

I would pull the spark plugs out and look at them closely to see if there is any evidence of carbon tracking. To correct this condition, it is necessary to change both the spark plug wire and the spark plug at the same time on only the cylinder involved. Changing only the spark plug or only the spark plug wire will not prevent the carbon tracking from recurring. Carbon tracking will happen again in the same location much quicker if half of the track is still available. Recurrence of the same problem is likely in as little as 1,000 miles if the carbon track is not totally removed

You can check the PCM for stored misfire codes, P0300 to P0306. If the code was stored it may help point you to the plug(s) involved.

A partially clogged fuel filter may also cause these symptoms. I might suggest replacing the fuel filter and doing a fuel pressure and volume test to verify proper fuel pump operation.

If all else fails, drive the vehicle until the symptoms manifests themselves and then go to your mechanic and take him on a road test. You drive so you can show him under what conditions the symptoms develop so he will know what to look for.

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