1990 Bronco 5.0 surging

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Old 04-07-07, 07:25 PM
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1990 Bronco 5.0 surging

I have a 1990 Full size Bronco 5.0 EFI and when I shut the a/c off I have a rise in the rpm then a drop. It does not matter if i am driving or what rpm I am at the time. The dealer does not have a clue or does any mec I have brought it too. I replaced the IAC motor, the only other thing I can think of is that I have a problem with ECU, Any suggestions? Thanks,Dean
 
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Old 04-07-07, 09:51 PM
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RPMs will always differ when turning on and off A/C. How many RPM's is it fluctuating?
 
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Old 04-07-07, 10:55 PM
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about 1000rpm's, it almost feels like a stall, when I am on the hyw and I switch off the a/c I lose power for a split second and then run ritch for a few seconds(I can tell by the smell)
 
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Old 04-08-07, 08:32 AM
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If there is a bad AC expansion valve, it will put a strain on the engine like you are describing. I believe these valves are located under then dash, but I am not completely sure.
 
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Old 04-08-07, 05:42 PM
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Could it be a bad ecu? I know the circut for the iac motor and the a/c run though it?
 
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Old 04-08-07, 07:11 PM
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I doubt it. If the ECU was bad, you would probably have more problems then you do now.
 
 

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