Hard Starting '91 Explorer
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Hard Starting '91 Explorer
Recently I have been having trouble with my wife's 91 Explorer 4.0 5-Speed not wanting to start when warm. I pulled the codes and it has code 42. This means that O2 sensor voltage is too high, meaning a rich condition. I know that when a motor is running rich the oil coating the cylinder walls can be washed away and theoretically cause hard starting, especially when the motor is warm. What do you guys think?
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Joined: Oct 2003
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From: Gilbert, AZ
Common on first gens is an intake leak. I know, i had one with the same problem. This could expand when the engine is hot. This would in turn cause the fuel mixture to be rich in turn causing the o2 sensor to report high voltage. What condition is the engine in?
Sounds a little simpler than that though. Have you checked the starter, solenoid switch, battery cables, and battery?
Sounds a little simpler than that though. Have you checked the starter, solenoid switch, battery cables, and battery?
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First off, thanks for the advice. The engine is in pretty good shape, only 125,000 miles, and it was pretty well taken care of. I have also replaced the, alternator, starter, solenoid switch, batter cables, and battery all in the last 8 months, isn't great how everything goes wrong at once? They are all still good.
It looks like I will have to check for an intake leak. Do you mean a leak in the gasket, or a crack in the manifold itself. God, I hope it is not a crack in the damn manifold.
It looks like I will have to check for an intake leak. Do you mean a leak in the gasket, or a crack in the manifold itself. God, I hope it is not a crack in the damn manifold.
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Joined: Oct 2003
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From: Gilbert, AZ
No problem 
Well, I dont want you to start working on it based solely on my advice, although it is damn flattering hehehe. Anyway, i mean a leak in the gasket. Your manifold itself is not likely cracked, although it is possible, mine wasnt, just a leaky gasket. Have you checked everything to do with the fuel side? Fuel filter, fuel pump, fuel pressure regulator, fuel injectors? All can cause a hard start and will run the engine rich if faulty.
Well, I dont want you to start working on it based solely on my advice, although it is damn flattering hehehe. Anyway, i mean a leak in the gasket. Your manifold itself is not likely cracked, although it is possible, mine wasnt, just a leaky gasket. Have you checked everything to do with the fuel side? Fuel filter, fuel pump, fuel pressure regulator, fuel injectors? All can cause a hard start and will run the engine rich if faulty.
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Plugs and wires are good, about 8 months old as well. I did a pretty extensive electrical tune-up on this thing over the summer. Fuel filter was changed about a year ago. As for the fuel pump, pressure regulator, and injectors, I have no idea.
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