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Magava

No Power when Engine is cold - 525i

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Hello all,

I have a 1986 525i with an M30 L-Jetronic.

My issue is that when the engine is cold the car just wont go. Even if you floor the accelerator it will not get past 40 km/h and revs wont go past 3K. As the engine heats up it keeps improving and once its at operating temperature the car is a rocket. This usually takes about 10 minutes.

I've lived with it like that so far as once the car is warm its fine, but its annoying when you first get going and you are backing up traffic so people think its coz you are driving an old pile of junk, not knowing its actually a beast! :D I have replaced the TPS, bought new spark plug wires, serviced the injectors (I think they need to be replaced all together), refurbished the MAF, still no change. I live in a tropical climate so the problem is not the ambient temperature.

Any help would be greatly appreciated.

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Your engine uses several water temperature sensors to inform the engine management system how things are going. I think your car, judging by the date uses two sensors, one to control the cold start injector (, the Thermo Time Switch, which is probably not the problem) as you can start the car, all be it in reasonably warm conditions. The more likely candidate is is Water Temperature Sensor which monitors the coolant temperature under all other conditions, which lets the engine management system (LE-Jetronic) adjust the mixture until its up to temperature and while its running.

 

http://bmwfans.info/parts-catalog/E28/Europe/525i-M30/1986/browse/fuel_preparation_system/control_unit/ shows the part numbers. 

 

You can fool the system into thinking things are up to temperature by disconnecting the WTS connector and jumping the pins within the connector, to test this theory.  

 

Edit. I'm surprised that it takes so long to get running ok. It may be that you also have water thermostat issues. What does the water temperature gauge look like once it gets running okay. Be aware that it will appear to be a bit low if things are ok. About 10:30-11.00 if it was a clock.

Edited by JohnH

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Hi John,

 

I already replaced all three sensors that are above the coolant housing so I doubt that could be the problem. From what you said, I took out the thermostat and it seems that it is locked in the open position so I'm guessing that's the issue?

 

I can't check the temperature gauge because mine doesn't work! :lol: I just fill up the coolant bottle and drive away! I've been trying to find a working gauge but its proved difficult without having to buy the whole instrument cluster.

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it could be your service indicator board that stopping some the the dials working. Ivo sells a replacement one now which need no maintenance as it is batteryless. 

 

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