91 740 Turbo Engine Idle/Air Temperature Sensor

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Old 11-13-2018, 07:06 PM
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Default 91 740 Turbo Engine Idle/Air Temperature Sensor

Hello, every one.
I have a 1991 740 Turbo with about 250K miles. It seems to start OK, but once the engine warms up to operating temperature, and I have to stop at a traffic light, the engine idle "hunts", and upon pressing the accelerator to go, the engine is underpowered and falters. If I accelerate very gradually, the engine seems to gain power and functions almost normally. I have replaced the oxygen sensor, cleaned the MAF sensor, the throttle body and plate, and the IAC valve, and replaced the radiator thermal switch. Is the ECT sensor the cause? Also, where is the Air Temperature Sensor on this car, and is there a Manifold Air Pressure sensor on the 740 Turbo models? Thanks in advance.
 
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Old 11-13-2018, 09:23 PM
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MAP and Air Temp Sensors are a Regina thing. your 91 Turbo has Bosch LH 2.4 injection, which uses coolant temp, crankshaft position, and MAF as its primary inputs.

if the MAF is defective, cleaning it won't fix it. The IAC only affects idling, notthing when running.
 
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Old 11-14-2018, 12:51 AM
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You may have a bad fuel pump, may be a bad MAFS... as a second choice.
 
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Old 11-14-2018, 01:29 AM
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Originally Posted by pierce View Post
MAP and Air Temp Sensors are a Regina thing. your 91 Turbo has Bosch LH 2.4 injection, which uses coolant temp, crankshaft position, and MAF as its primary inputs.

if the MAF is defective, cleaning it won't fix it. The IAC only affects idling, notthing when running.
Originally Posted by lev View Post
You may have a bad fuel pump, may be a bad MAFS... as a second choice.
Thank you for the replies. One European parts site was trying to sell me the air temperature sensor, which until now, I thought without certainty is only used in the Regina system, i.e., non-turbo models. I already have a new ECT sensor to install, and a thermostat as well, both European manufactured. If they do not correct the issue, I will have to plunk down the $300 for the AMF sensor. Thanks again.
 
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