By Bill Siegmann
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“The customer who came in was frustrated because this was the third repair shop he had been to - and no one had been able to solve the problem.”
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Vehicle:
1994 Oldsmobile 98 Regency
Engine:
3800 L
Symptom:
Intermittent lack of power on acceleration
The customer who came in was frustrated because this was the third repair shop he had been to - and no one had been able to solve the problem. His complaint: an intermittent lack of power on acceleration from a stop.
He said his car ran rough at idle and would sometimes stall. After restarting the engine or if he cycled the ignition key, it would sometimes start and run fine. But not always. No service had been performed prior to the start of this problem. Parts replaced so far: PCM, MAF sensor, O2 sensor and fuel pump.
So shop No. 3 went to work. The technician did a scanner check and found all readings normal except a history code 44 was stored in memory. The technician checked the MAF sensor resistors and throttle body screen for debris - it had been cleaned. Thinking the problem might be fuel related, the technician prepared the vehicle for a road test by clearing the code, installing his fuel pressure gauge taped to the windshield, and installing the propane tank setup with a half-inch hose into the air cleaner housing to add fuel, hoping to find a diagnostic direction.
After several road tests, on a hard acceleration from a stop, the Olds finally bogged hard and idled rough. Fuel pressure was steady, and by adding propane, the engine came back to life. The engine stalled, restarted and ran fine for the rest of the day. Before the engine stalled as if it were running lean, the scanner indicated MAF grams lower than normal, the O2 sensor at 80 Mv, and the calculated injector pulse width was at 4. The PCM wasn't trying to add fuel! The next time it acted up, the technician disconnected the MAF sensor and the engine ran fine. Power, grounds and terminal grip at the MAF sensor checked out OK.
The technician then found he was able to power brake the engine hard in the shop and get it to bog intermittently. At this point, the technician removed the bellows at the throttle body to add a burnable carburetor cleaner since the propane was being used on another vehicle at that time. With the engine still running, the technician found - to his amazement - that an old oil change sticker was sucked up against the throttle body screen-sensor side, blocking airflow to the MAF sensor! This, of course, caused low airflow by the sensor and as a result: lack of fuel. The technician removed the plastic sticker with the engine running - and the problem was solved.
Long lesson short: Always disassemble and check for any debris in the air intake system, including the bellows or intake snorkel. You never know what you might find lurking there.
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