Ford Forums banner

1 - 14 of 14 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
My 1995 Fairmont will intermittently cut out while driving. This usually happens when the engine is at operating temp and after a short stop (like quickly stopping at the shop to buy milk or something). It also normally happens shortly after driving off while the speed is still slow. If I try to restart, the engine will start but it runs very rough (actually sputters) and cut out again. This is when I start it from the On position on the ignition. Only if I turn the key in the ignition all the way to Off, and start it then, will it start normally and run as if nothing is wrong.

I pulled the error codes and it does not report anything wrong, except code 126 which is MAP sensor out of range. I recently replaced the MAP sensor with a new one and I doubt that it could be the problem. The previous MAP sensor was faulty and I had almost no power, the engine was running rich the whole time, and I only got 5 km to the litre (20 litre per 100km) on the open road. Since replacing the MAP sensor, the power is great, and fuel consumption is now 10km to the litre (10 litre per 100km) on the open road.

Before the MAP sensor replacement, the car did not cut out like it does now. This only started after the MAP sensor replacement.

Any ideas what may be the problem?
 

·
Super Moderator
Joined
·
3,601 Posts
It will be the MAP sensor or possibly the wiring to it. The stalling is consistent with a faulty MAP sensor (for example http://www.autotap.com/techlibrary/solving_intermittent_stalling_problems.asp for example) and diagnostic codes are usually correct. If it's a new rather than used MAP sensor, and you cleared the codes before or after replacing it is likely the wiring to the sensor or a leak in the hose to the sensor (or the hose is disconnected at one end).
 

·
Super Moderator
Joined
·
3,601 Posts
Also check the small plastic vacuum line elbow that screws into the inlet manifold immediately below the throttle body is not cracked or broken as the often crack or break and a vacuum leak there will also adversely effect the performance of the MAP sensor.
 

·
Super Moderator
Joined
·
3,601 Posts
To check the wiring with the ignition switch off disconnect the harness plug from the MAP sensor. Then turn the ignition on and check for voltage at the orange black wire of the wiring harness plug (should be between 4 and 6 Volts). If 0 volts check for a blown fuse (remove fuse and check for continuity with a multimeter; don't just visually check). With ignition off also check for continuity between the centre wire of the plug and pin 34 of the ECU. Then check for continuity between earth and the third wire on the plug. Next reconnect the wiring harness and back probe the MAP sensor plug at the centre pin while it is connected to the sensor and use an oscilloscope, frequency meter or a multimeter with a frequency setting. The readings at sea level should be:

Ignition on 0.155 to 0.156 kHz
Engine idling in neutral 0.101 to 0.103 kHz
Engine revving in neutral 0.90 kHz
Engine Idling in Drive 0.105 0.106 kHz
Engine Idling in Drive Air Con on or Power Steering in use 10109 to 0.111 kHz

If you don't have something that can read frequencies but have a multimeter with a tacho function (or have a hand held tacho) set it to the 6 cylinder range and connect it by back probing between the black/white signal wire and the blue/yellow return wire. With the vacuum hose disconnected from the sensor it should read 300 to 320 rpm. If you apply 68 kPa of vacuum to the sensor vacuum port the tacho reading should change to 200 to 230 rpm with a smooth (not immediate) change between the with and without vacuum reading.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #7
I have not tested the MAP sensor yet, but I cleared the error codes and drove around town. I had the same issues again (as per the details below). Afterwards, I pulled the error codes again in KOEO and KOER and it gave my no error codes at all. Now for the problems I encountered:

Although it did not actually cut out, there were a few times it stumbled when trying to pull away at stops, traffic lights, etc. To prevent it from stalling, I have to completely take my foot off the accelerator, let i slowly start to move under idling, and then very very slowly start to use the accelerator. My previous experience was that any attempt to accelerate normally will definitely make it stall.

While this is happening, I have to smile and wave to all the nice people in the car behind me giving me middle finger greetings.

After about 10-15 seconds of feather footing the accelerator, it will come right and drive normally. Although I will test the MAP sensor, I do not think it is the problem as it is brand new and was installed by a qualified auto-electrician that checked the wiring and connector plug as well.

Can it maybe be the coil pack/leads or TPS ? Any suggestions will be very welcome.
 

·
Super Moderator
Joined
·
3,601 Posts
You may have a vacuum leak at the inlet manifold that closes up when the manifold gets hot. They usually at number 1 and/or 6 and at the bottom of the manifold where the manifold joins the head. They leak because the nuts get loose with time and the gasket partially burns out. You won't find these leaks by spraying engine start, oil, butane gas etc around the manifold because the leak is so small and at the bottom so gravity stops things being sucked in. Even smoke tests don't work well. You need to get a metre or so of windscreen washer sized tubing and stick one end in your ear while moving the other end around the inlet manifold especially at the bottom of cylinders 1 and 6. Do this with the engine idling and try it with a cold and hot engine; if there is a leak you will hear the distinctive sucking noise through the tube.

If the stalling happens on slow (and even slight) turns rather moving straight ahead then the power steering switch, that up the engine revs to counter the power steering load, may have failed or become unplugged.

Also check that plastic vacuum tube elbow immediately below the throttle body.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #10
Thanks Aussiblue. Checked for vacuum leaks but there are none.

Finally met a retired mechanic who knows the Fairmonts very well. Seems that the major problem was base timing. (Although it is an EF engine, it has a distributor and not coil pack). He set the timing and performance is now excellent. Occasionally the car will start to run rich and feels like it floods when trying to accelerate. A quick restart will remedy that immediately. Still do not know why it does that.
 

·
Super Moderator
Joined
·
7,785 Posts

·
Super Moderator
Joined
·
3,601 Posts
(Although it is an EF engine, it has a distributor and not coil pack).
If it is a stock EF it should have EDIS (Electronic Distributorless Ignition System). If it has a distributor and coil it would appear that either an engine from and EL with the EEC-V system has been retrofitted or the EEC-V system has been retrofitted to replace the EDIS system. Are you the original owner or, if not, have these problems existed from when you acquired the car?
 

·
Super Moderator
Joined
·
3,601 Posts
Also check the small plastic vacuum line elbow that screws into the inlet manifold immediately below the throttle body is not cracked or broken as the often crack or break and a vacuum leak there will also adversely effect the performance of the MAP sensor.
Have you checked this yet?
 

·
Super Moderator
Joined
·
3,601 Posts
Also next time the tank is low try briefly running it without a fuel cap. The fuel cap has a one way vent valve that allows air into the tank but doesn't let fuel out. If this vent fails the fuel pump will have difficulty overcoming the vacuum and the car will stall.
 
1 - 14 of 14 Posts
Top