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1989 740GL Running Rough

Hi all-

I had an episode today with my 740 with ~197K miles. Started fine, but when I pressed the gas pedal, the engine would rev and drop off repeatedly. If I feathered the gas, it ran fine, but I had to pull off to the side of the road to travel up a hill since I couldn't give the car any gas. After restarting the car for the 3rd time, the car ran fine, accelerating without a hiccup. Add into the equation that my mileage has dropped to the high teens the last 2 tankfuls, a check engine light that will be checked next week, and a new catalytic converter last month. Any thoughts?

On a positive note, I had no trouble driving in the snow last month when we got 2+ feet of snow in Buffalo. All my neighbors appreciate the Brick. Thanks in advance for your replies-

John

Reply to
John
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Hi John, Have you checked your fuel filter lately? If you haven't had any problems since, maybe you got some bad gas? Hope it has cleared up. jimmy

1990 740 GL wagon
Reply to
jimmy

Don't quite understand 'rev and drop off'. I assume it is A. Automatic B. Injection with lambda sensor

I guess it is loosing power because of too much or too little fuel, or possibly bad ignition.

From the previous bad economy it sounds like its running very rich (progressively so) or too lean at some points, which may have damaged the cat and be the reason the check light is on. Air mass meter would be the first suspicion, maybe lambda sensor.

-- Tony

Reply to
Tony

Hi guys, thanks for your responses. Tony, you're right on both A and B. And AMM was replaced about 100k miles ago. I dumped in a bottle of fuel injector treatment and the problem cleared up in 20 miles. I'll find out more when I get the check engine light checked. Thanks again-

off'. I assume it is

Reply to
John

Update on the old girl.

My business trips took me by the Indian Reservation, so I would fill up there, saving ~25 cents a gallon. When those trips stopped, I went back to my usual station. Right off the bat, my mileage went from 16 to 23 mpg. Check engine light was for the throttle body, adding a couple more mpg. I was never a fan of the different station/same gas theory, but now I'm a believer.

off'. I assume it is

Reply to
John

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