April 13, 2015 02:29AM
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Registered: 9 years ago
Posts: 8 |
I have a 1989 318I 2 door Auto that stalls infrequently.
I have replaced the Battery, Spark Plugs, Fuel Filter, Starter recently and Fuel Pump 12 months ago. The fuel filter was extremely filthy. After the car had been stationary for 6 months The car starts first time. When driving on Highway it cruises extremely well. No loss of power. On the odd occasion the car will stop. No chugging or stuttering... just lack of power and the engine stops. The engine will start again on the the first or third try. The issue has become more frequent in the last week. (once per day... usually when coming to or starting from a stop. When the fuel tank is full or near empty. The car was Any ideas! |
April 13, 2015 03:27AM
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Registered: 9 years ago
Posts: 136 |
Next time this happens, watch the instruments carefully. If the tachometer drops suddenly to zero, you have a power issue
to the engine computer. If the econometer goes all the way left, it is the computer that cuts the fuel since it does not think it has any air (air flow meter issue). If it goes to the right, it could be a fuel supply problem. I would also check the throttle switch. Make sure the throttle is closed with the foot off the throttle. The two leftmost contacts in the swich connector should be linked at this point. Add some throttle, and check that they are no longer linked, and that the throttle valve opens. Switch ignition on, and check that the idle control valve vibrates. |
April 13, 2015 04:25AM
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Registered: 9 years ago
Posts: 8 |
Thanks///
Just to add some more information. It did stall whilst slowing down from 100kph or 50mph. just a second and it resumed with no issues. I thought it might be a fuel blockage or similar. When it stalls - the Alt and Oil lights do not come on. The tacho goes just above Zero. As if the car is coasting. It did a very small back fire on one occasion when restarting. I will check the air flow meter issue and the throttle switch. I will check that the idle control valve vibrates as soon as I can find out where it is. How do I check to see if there is a power problem to the computer? Edited 1 time(s). Last edit at 04/13/2015 04:29AM by Kicks. |
April 13, 2015 04:30AM
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Registered: 9 years ago
Posts: 136 |
The idle control valve sits between the engine and the firewall, rather high on the intake side. Looks like a small metal cylinder with a cable connection.
The most common cause of engine computer power issues is a faulty relay under the cover on top of the firewall. There are usually three relays there. You could try to swap the two equal ones, and see if it makes a difference. Edited 1 time(s). Last edit at 04/13/2015 04:32AM by Ove Kvam. |
April 13, 2015 09:17PM
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Registered: 9 years ago
Posts: 8 |
April 15, 2015 12:28AM
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Registered: 9 years ago
Posts: 8 |
April 15, 2015 12:52AM
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Registered: 9 years ago
Posts: 136 |
It could be an issue with the idle control valve, but the most common cause of rough idle is air leaks causing the engine to get access to unmetered air. If you have a can of start gas, you could try to spray it on various air hoses while the engine is idling. If it suddenly revs up, you have found your leak. |
April 15, 2015 01:00AM
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Registered: 9 years ago
Posts: 136 |
There is also one more test that can be done to check that the idle program kick in correctly. My 318i was a manual, where this
is very easy, but I guess it can somehow be done with an automatic as well by manually selecting a low gear. The trick is to let the car coast at speed, with the RPM dropping slowly. At high RPM, the econometer should show no fuel consumption (fuel cut). As the RPM gets closer to the 800 RPM idle speed, the engine computer should switch to the idle program, and start feeding fuel to the engine. I guess it happens around 1200 RPM or so. For this to happen, the computer needs to get the "no throttle" signal from the throttle switch. It will also start working with the idle control valve to regulate the air supply to the engine. |
April 15, 2015 01:17AM
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Registered: 9 years ago
Posts: 8 |
April 15, 2015 02:15AM
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Registered: 9 years ago
Posts: 136 |
April 15, 2015 05:22AM
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Registered: 15 years ago
Posts: 187 : Bucharest, Romania |
Do the lights go off when the engine stalls ?
I had such an issue once, caused by a loose wire that was hitting the chassis causing a short. Every time it would stop, I would open the hood and check everything to find nothing. Until one time it happened at night and I found the moving cable by the sparks it was making. -- A physics truck just turned over outside. There's physics everywhere! |
April 15, 2015 06:11AM
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Registered: 14 years ago
Posts: 799 : O Porto |
This kind of problems usually routes to bad wiring and electric contacts.
We have too many old plugs and wiring, something may fail intermittently and drive people nuts. All fuses and relays were checked. Make sure the ignition wirng is good. Leaky air or vacuum pipes may cause trouble as well. Oil dipstick counts as a vacuum leak when removed. An odd thing, when I first bought the old Mercedes Benz after siting idle for a while, it was plagued with minor electric problems, now most problems cured by itself. Good luck! |
April 15, 2015 07:08PM
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Registered: 9 years ago
Posts: 8 |
Thanks for all the help.
Checked all the vacuum and electrics... cables, fuses and connections. Most of the vacuum tubes have been previously replaced. Fuses removed checked and reinserted. Attacked the engine with hairspray. Neighbours thought it strange when I started. Nothing transpired. Will drive again and keep you posted |
April 16, 2015 03:13AM
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Registered: 9 years ago
Posts: 8 |
April 16, 2015 02:14PM
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Registered: 15 years ago
Posts: 670 |
April 17, 2015 09:45PM
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Registered: 9 years ago
Posts: 8 |