740 w/ Regina runs terrible when hot - stalls out when stopping. Probably could run on the freeway for hours, so it's an idle issue. I have replaced MAP sensor where the air intake is, tonight replaced coolant sensor under #3 intake, but that didn't solve issue. What is meant for air temp sensor? IAC? Need help. Thank you.

Hi Bonzo,

Bendix Regina (Fuel Injection) is a code presented using the OBD-1 socket 2 test unit



https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

So, on the FAQ Web Page: Table 3: Regina Fuel Injection Fault Codes.

"1-2-2: Signal missing or faulty to/from air temperature sensor Air temperature sensor"

The Rex ignition control has no corresponding fault code as it does not use the

Image of Intake Air Temperature Sensor:


Another view:


Another view:


The fault code may condemn a fault in the wire harness between the air temperature sensor and the Regina ECU controller. Wire line corrosion at any connector?

At any rate, this PDF file shows the location of the Regina air temp sensor (copy asd paste):
https://www.matthewsvolvosite.com/forums/download/file.php?id=8581

The air temperature sensor is:

FCP Euro Gebuine Volvo) 54$:
https://www.fcpeuro.com/products/volvo-air-temperature-sensor-models-with-regina-1389556

Tasca Volvo Parts 47$
https://www.tascaparts.com/oem-parts/volvo-volvo-intake-air-temperature-iat-sensor-1389556

iPd (outa stock - appears OEM) 32$:
https://www.ipdusa.com/products/9281/120676-intake-air-temp-iat-sensor-740-940-rex-regina

https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#ReginaAirTemperatureSensor

I dunno who makes this part. I'll guess Bendix. Bendix Regina (fuel - OBD socket 2) has an error code specific to this sensor, so replacing sensors where the ECUs do not report a corresponding fault may not solve your symptoms.

Also, in your Regina air filter air box, upstream (dirty air side) of the air filter is a preheater control flappy valve controlled by an air thermostat made by Wahler (Whaler?). These will fail to all hot all the time, and may cause the air temp sensor to fail or misread ambient air temp conditions so the Bendix engine control in your 1991 Volvo 740 operates well no matter the air induction intake piping temp.

So, as your local and state emissions control allow, you can:
- Replace the air temp sensor controlling the preheat flap valve
- Remove the silver accordion hose between the air filter box and the exhaust manifold heat shield, and then remove the assembly from your air box.

So, some example air temp preheat controller thermostats made by (Borg-Warner) Whaler (PN 70411)





Tasca Auto Parts - 49$:
https://www.tascaparts.com/oem-parts/volvo-thermostat-1266826
(May be made in Europa at that price?)

iPd 13$:
https://www.ipdusa.com/products/5451/103083-airbox-thermostat-valve

FCP Euro - 10$
https://www.fcpeuro.com/products/volvo-engine-air-box-thermostat-1266826

Though I expect with more 700-900 ownership expereince like Spook can provide more insight into Bendix Rex / Regina foibles.

Hope that helps.

Questions?

Gigafactory Hopeful MacDuffed.
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OK. So I did already replace the first sensor. I forgot what it was called. It's located in the same place as my AMM in my 240. But I will try the 2nd part you mentioned after some cleaning of TB, fuel system etc.

So, wait, what?

Regina Temp Sensor - Volvo 1389556

This:


Is the air temp sensor that installs into the AMM / MAF looking like thing that appears in a location similar to the Bosch AMM / MAF.

The fault code you have is related to this sensor. Either the wiring is at fault, the sensor is at fault, and / or the air flappy valve thingy in your air filter box is stuck to preheater open, all the time. Bad in the hot, hot hateful hot Summer. (I despise Summer.) Ambient air temp + preheated air your engine breathes in ....

So, you did or did not replace this sensor? If yes, did you reset the fault codes using the OBD procedure in your service manuals or the OBD info in the FAQ?

Did you observe the preheater flappy valve in your air filter box? Does preheated air enter the air filter box? Is the flap valve stuck to preheat air only? So replace the thermostat or remove the silver accordion hose between the exhaust manilld and air box? And you can remove the prehreater flap valve assembly as it clips into the air filter box. As your state and local emissions regulatory control allow.

I dunno hhhwhut Ohio demands.

https://en.wikipedia.org/wiki/Vehicle_inspection_in_the_United_States

So, I guess you no longer require emissions inspection. yet your 1991 Volvo 740 will run top-notch with all emissions controls in fine fettle. Though you could rid yourself of the cat converter, yet you DO want the oxygen sensor working well.

So, lettuce know how you make out so we know it works all proper if you need to replace the Regina air temp sensor, as images, above. You may not have needed to replace the otrher sensor that are unrelated to the fault code.

Hope that helps you and your Happy Sat-Your-Day!

Silver State Macduffed?
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I replaced the sensor that you show there. My problem remains so I am going to clean TB. BUT now idle is extremely low, stalls now a couple times when starting first thing in the morning. Idle seems to be at 200-300! Do I need to disconnect battery to reset or something? Ideas? Thank you.

Hi Bonzo,

Checking the OBD codes again may help if other issues persist or new or additional codes set. I'm unsure whether the Bendix Rex (ignition control) and Regina (fuel control) can self-clear a code if the fault cause, related to the fault code, is re-mediated (corrected or repaired).

The performance change may very well indicate the sensor, as indicated in the fault code, was at fault. Yet adjacent issues may cause poor idle when cold or at any temperature.

You can follow the OBD fault code clearing procedure in the Electrical: OBD page in the FAQ. Though the fault cause, or causes, if they persist, will continue to cause idle issues.

How does it run, though. When you take up drive and the engine warms up? Any change?

You indicated you cleaned the throttle body before. You may want to inspect the idle air control valve.

I suspect that without the Air Temperature sensor input as out of range or failed, associated with socket 2 Regina fuel OBD code 1-2-2 you ofiginally received, versus the engine coolant temperature sensor (ECT) used by the Bendix Regina fuel control. So, your 1991 Volvo 740 Bendix Regina was in "limp home" (a Volvo term used more so for Bosch) with the input.

When it comes to Bendix Regina / Rex, the 700-900 FAQ is sort of anemic:

https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

The listed Bendix Regina fault code in ...:

"Table 3: Regina Fuel Injection Fault Codes. Read these from socket 2:"

... does not indicate symptoms, whether a fault code illuminates the check engine light, and the specific cause. So, you have some guess work.

Check for any persistent fault codes in socket 2 as before with Regina. Repeat the procedure until no new fault codes, if any. Perform the same in OBD Rex ignition socket 6.

Clear the codes as on the FAQ OBD page, or remove the battery cable, let set for however many minutes folks here indicate.

There is not a power stage in Bendix Rex ignition. There is a square ignition signal amplifier and distribution (step-up) coil that sends the high tension (high volt, low amp) through the distributor to the spark plugs. The signal originates from the Bendix Rex ignition control unit (ICU) box based on input from the crank position sensor, like that used in Bosch EZK116 we all know well.

How can I tell if my Volvo has Bosch or Regina Fuel Injection?

https://www.ipdusa.com/techtips/10085/how-can-i-tell-if-my-volvo-has-bosch-or-regina-fuel-injection

You can clean the throttle body and the idle air control (IAC).

Though a check of electrical connections.

Verifying no air induction intake leaks from air filter to air intake manifold gasket. Also, ensure your PCV is not leaking vacuum. I remove the large hose from the accordion style hose near the TB, and the small hose at the intake manifold, and seal the small hose, and with oil filler cap secured on, blow through it. Should not be able to. Yet easily blow through it with oil filler cap off.

You may need to check or adjust the throttle position switch, yet doub t this is your issue.

If the issue persists when warmed, the air filter box preheater control flap valve thermostat works well (replace it like every two years now - Whaler? or Calorstat? 70411, Volvo PN 1266826)

https://www.fcpeuro.com/products/volvo-engine-air-box-thermostat-1266826)

I'm unsure how much Regina is affected in cold weather with the air box preheat feature working well of not. In hot weather, as the flap valve fails to hot in 240s, 740s, 940s (Turbos 700-900s don't have them, non-Turbos including Rex/Regina does.)

Some FAW matter for you .... yet does not treat Bendix specifically.

https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm

https://www.brickboard.com/FAQ/700-900/EngineSealsBeltsVent.htm

Some Regina info with links to more Regina info:
https://www.brickboard.com/FAQ/700-900/EngineFuelinjection.htm

Some general notes, yet not Regina specific:
https://www.brickboard.com/FAQ/700-900/FuelSystem.htm

Else, I'm unsure. May need Spook and others more currently familiar with Rex / Regina to reply.

Lettuce know whut you encounter.

Pilot Light Goes Out A Lot. Pilot Thermo Couple Failure (Replaced By Gulag SlumLord) or the Valve Itself.
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Does your 740 have a spark amplifier on the driver side inner fender? If so, they get faulty when failing . Runs fine when starting out and then overheats. Requires heat sinking compound when mounting which dries out. I know my 89/ 740 has one. Yours might be part of the ignition coil.

"...What is meant for air temp sensor? IAC?..."

Air Temp Sensor = On a Regina car it's the sensor in the intake duct between the air filter and the Throttle Body. Generally not failure prone.

IAC = Idle Air Control, allows intake air to bypass the throttle plate in order maintain idle level. Prone to getting dirty and not working properly. Clean it out with carb cleaner along with the throttle body as Randy suggested.

Once everything is cleaned out make sure the throttle position switch is clicking into the idle position properly.

Reading material:

https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#PoorPerformanceIdleSurgeandHuntDirtyThrottleBody
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

Thanks. I looked at the link. I will start by adding a bottle of Techron after filling up tank. Then on to other suggestions.

Is it safe to assume that you have cleaned the throttle body?

I have cleaned the TB in the past but not recently. I will try that although I didn't think it would cause these specific issues.