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1990 740GL, 170,000 mi.
The car runs fine, then will suddenly lose power and idle very rough. Sometimes it will kick back in and be fine, other times it will eventually stall and not restart for a while. I've had it checked twice at a Volvo Specialist. They replaced the fuel pump relay, cleaned connections, checked fuel pump pressure, cleaned the throttle body assembly and replaced throttle body sensor.
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when it doesnt start, does it have spark. i need to know that info.
It does have a spark, it will generally start and idle very rough for 30 seconds or so before stalling again. If I leave it for a couple of hours it usually will start and run ok for a while.
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sounds like possibly a mass air flow meter. outside chance maybe a fuel computer too.
Thanks for your help, I have one more question for you. I disconnected the idle air control motor, when i reconnected it to engine idled very high to low. How do i reset the system? Also, according to my Chiltons book, my model does not have a mass airflow meter, is this correct?
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well if you have a regina system, you might have an ambient temperature sensor. located where the mass air flow meter is. this i can only tell from looking at the car. unplug the radio for 1 min, then reconnect, and it should clear the adaptives for the idle speed motor. Last night the car lost power again, I pulled over and it idled fine, when I tried to drive it was extremely rough, no power, loud popping similar to backfiring but coming from the engine not the exaust.
Thanks again, sorry to keep bothering you, just put a lot of money into the car and am trying to get this last problem solved. I tested the ambient temperature sensor and it appears to be good. Last night the car lost power again, I pulled over and it idled fine, when I tried to drive it was extremely rough, no power, loud popping similar to backfiring but coming from the engine not the exaust. The problem does not seem to happen when the car is cold, only after it has warmed up. If it is the fuel computer should the Volvo machanic be able to test it?
Answerpopping is a timing issue, perhaps your distributor cap is full of oil, or burnt with carbon? maybe your engine speed sensor is getting weak, it can work but a magnet is affected by extreme temperatures, heat and cold the like. you might just put one of these engine speed sensors in and monitor. as to the testing of the computer, no real testing can be done, except for drive the car with the new computer. tests like this are very subjective, if the car is working fine, its going to test fine. if you only have a short window to evaluate, then you have much more difficulty.
