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volvoexpert1, ASE Certified Technician
Category: Volvo
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Experience:  Volvo Master Technician with 15 years excusively with Volvos. Also ASE L1certified for over 10 years.
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Volvo 940 GL (non-turbo): 1992 volvo 940 with regina fuel system.

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1992 volvo 940 with regina fuel system. It appears to go lean when depressing the accelerator. At the same time the injector pulse width nearly doubles. The map sensor voltage increases by more than 2.0 volts. The O2 sensor voltage drops to the .060-.080 range. And the fuel pressure at the rail is in the 35 pound range. On opening throtle in gear, engine stumbles and backfires.


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Customer: replied 4 years ago.
I'm still in need of an answer.
Hello! The fuel pressure is about right, but make sure it increases when the throttle is suddenly opened. I suspect the MAP sensor. Its either not reacting quickly enough or just faulty. Without a mass airflow, this is the key load sensor. Sometimes the plastic vacuum line gets restricted, you can try a piece of vacuum hose. Run a wire through the vacuum nipple on the intake to make sure it is clear. If still no good, try another MAP sensor. Its the same part GM used back in the day, so should be readily available.
volvoexpert1, ASE Certified Technician
Category: Volvo
Satisfied Customers: 1007
Experience: Volvo Master Technician with 15 years excusively with Volvos. Also ASE L1certified for over 10 years.
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Customer: replied 4 years ago.
Found several large cracks in the union(rubber) between the MAP sensor and the hard plastic line to the manifold. Now I have an idle of 2000 rpm. Let you know what else I find.
When you get vacuum straightened out, no leaks or restriction, do a battery disconnect or pull fuse #1 fir 10 minutes to reset adaptive memory in EFI module. Then see how it runs.
Customer: replied 4 years ago.
Thanks for the tip on the ecu. Found a faulty throtle switch and cleaned the throtle cavity(where the plate rests), idle came down to 1040 rpm, still a little high. The good new is that the inability to achieve any acceleration from a stop has been cured. I should have found that vacuum leak earlier, I had already replaced three of those rubber couplers due to poor condition but I missed the one under the map sensor. Thanks again.

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